Illumos 5369 - arc flags should be an enum

5369 arc flags should be an enum
5370 consistent arc_buf_hdr_t naming scheme
Reviewed by: Matthew Ahrens <[email protected]>
Reviewed by: Alex Reece <[email protected]>
Reviewed by: Sebastien Roy <[email protected]>
Reviewed by: Richard Elling <[email protected]>
Approved by: Richard Lowe <[email protected]>

Porting notes:

ZoL has moved some ARC definitions into arc_impl.h.

Signed-off-by: Brian Behlendorf <[email protected]>
Ported by: Tim Chase <[email protected]>

13 files changed, 398 insertions, 389 deletions

diff --git a/cmd/zdb/zdb.c b/cmd/zdb/zdb.c
index 6e75d0c21..8572dae2e 100644
--- a/cmd/zdb/zdb.c
+++ b/cmd/zdb/zdb.c
@@ -1250,7 +1250,7 @@ visit_indirect(spa_t *spa, const dnode_phys_t *dnp,
 	print_indirect(bp, zb, dnp);
 
 	if (BP_GET_LEVEL(bp) > 0 && !BP_IS_HOLE(bp)) {
-		uint32_t flags = ARC_WAIT;
+		arc_flags_t flags = ARC_FLAG_WAIT;
 		int i;
 		blkptr_t *cbp;
 		int epb = BP_GET_LSIZE(bp) >> SPA_BLKPTRSHIFT;
diff --git a/include/sys/arc.h b/include/sys/arc.h
index 215c75b6d..25e2f0352 100644
--- a/include/sys/arc.h
+++ b/include/sys/arc.h
@@ -57,6 +57,36 @@ struct arc_prune {
 	refcount_t		p_refcnt;
 };
 
+typedef enum arc_flags
+{
+	/*
+	 * Public flags that can be passed into the ARC by external consumers.
+	 */
+	ARC_FLAG_NONE			= 1 << 0,	/* No flags set */
+	ARC_FLAG_WAIT			= 1 << 1,	/* perform sync I/O */
+	ARC_FLAG_NOWAIT			= 1 << 2,	/* perform async I/O */
+	ARC_FLAG_PREFETCH		= 1 << 3,	/* I/O is a prefetch */
+	ARC_FLAG_CACHED			= 1 << 4,	/* I/O was in cache */
+	ARC_FLAG_L2CACHE		= 1 << 5,	/* cache in L2ARC */
+	ARC_FLAG_L2COMPRESS		= 1 << 6,	/* compress in L2ARC */
+
+	/*
+	 * Private ARC flags.  These flags are private ARC only flags that
+	 * will show up in b_flags in the arc_hdr_buf_t. These flags should
+	 * only be set by ARC code.
+	 */
+	ARC_FLAG_IN_HASH_TABLE		= 1 << 7,	/* buffer is hashed */
+	ARC_FLAG_IO_IN_PROGRESS		= 1 << 8,	/* I/O in progress */
+	ARC_FLAG_IO_ERROR		= 1 << 9,	/* I/O failed for buf */
+	ARC_FLAG_FREED_IN_READ		= 1 << 10,	/* freed during read */
+	ARC_FLAG_BUF_AVAILABLE		= 1 << 11,	/* block not in use */
+	ARC_FLAG_INDIRECT		= 1 << 12,	/* indirect block */
+	ARC_FLAG_FREE_IN_PROGRESS	= 1 << 13,	/*  about to be freed */
+	ARC_FLAG_L2_WRITING		= 1 << 14,	/* write in progress */
+	ARC_FLAG_L2_EVICTED		= 1 << 15,	/* evicted during I/O */
+	ARC_FLAG_L2_WRITE_HEAD		= 1 << 16,	/* head of write list */
+} arc_flags_t;
+
 struct arc_buf {
 	arc_buf_hdr_t		*b_hdr;
 	arc_buf_t		*b_next;
@@ -71,15 +101,6 @@ typedef enum arc_buf_contents {
 	ARC_BUFC_METADATA,			/* buffer contains metadata */
 	ARC_BUFC_NUMTYPES
 } arc_buf_contents_t;
-/*
- * These are the flags we pass into calls to the arc
- */
-#define	ARC_WAIT	(1 << 1)	/* perform I/O synchronously */
-#define	ARC_NOWAIT	(1 << 2)	/* perform I/O asynchronously */
-#define	ARC_PREFETCH	(1 << 3)	/* I/O is a prefetch */
-#define	ARC_CACHED	(1 << 4)	/* I/O was already in cache */
-#define	ARC_L2CACHE	(1 << 5)	/* cache in L2ARC */
-#define	ARC_L2COMPRESS	(1 << 6)	/* compress in L2ARC */
 
 /*
  * The following breakdows of arc_size exist for kstat only.
@@ -146,7 +167,7 @@ int arc_referenced(arc_buf_t *buf);
 
 int arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp,
     arc_done_func_t *done, void *private, zio_priority_t priority, int flags,
-    uint32_t *arc_flags, const zbookmark_phys_t *zb);
+    arc_flags_t *arc_flags, const zbookmark_phys_t *zb);
 zio_t *arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
     blkptr_t *bp, arc_buf_t *buf, boolean_t l2arc, boolean_t l2arc_compress,
     const zio_prop_t *zp, arc_done_func_t *ready, arc_done_func_t *physdone,
diff --git a/include/sys/arc_impl.h b/include/sys/arc_impl.h
index e7068ea18..1f8351a67 100644
--- a/include/sys/arc_impl.h
+++ b/include/sys/arc_impl.h
@@ -107,7 +107,7 @@ struct arc_buf_hdr {
 
 	arc_buf_hdr_t		*b_hash_next;
 	arc_buf_t		*b_buf;
-	uint32_t		b_flags;
+	arc_flags_t		b_flags;
 	uint32_t		b_datacnt;
 
 	arc_callback_t		*b_acb;
diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index 1941044a0..7b34e6825 100644
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -495,50 +495,26 @@ static kmutex_t arc_prune_mtx;
 static arc_buf_t *arc_eviction_list;
 static kmutex_t arc_eviction_mtx;
 static arc_buf_hdr_t arc_eviction_hdr;
-static void arc_get_data_buf(arc_buf_t *buf);
-static void arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock);
-static int arc_evict_needed(arc_buf_contents_t type);
-static void arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes);
-static void arc_buf_watch(arc_buf_t *buf);
-
-static boolean_t l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab);
 
 #define	GHOST_STATE(state)	\
 	((state) == arc_mru_ghost || (state) == arc_mfu_ghost ||	\
 	(state) == arc_l2c_only)
 
-/*
- * Private ARC flags.  These flags are private ARC only flags that will show up
- * in b_flags in the arc_hdr_buf_t.  Some flags are publicly declared, and can
- * be passed in as arc_flags in things like arc_read.  However, these flags
- * should never be passed and should only be set by ARC code.  When adding new
- * public flags, make sure not to smash the private ones.
- */
-
-#define	ARC_IN_HASH_TABLE	(1 << 9)	/* this buffer is hashed */
-#define	ARC_IO_IN_PROGRESS	(1 << 10)	/* I/O in progress for buf */
-#define	ARC_IO_ERROR		(1 << 11)	/* I/O failed for buf */
-#define	ARC_FREED_IN_READ	(1 << 12)	/* buf freed while in read */
-#define	ARC_BUF_AVAILABLE	(1 << 13)	/* block not in active use */
-#define	ARC_INDIRECT		(1 << 14)	/* this is an indirect block */
-#define	ARC_FREE_IN_PROGRESS	(1 << 15)	/* hdr about to be freed */
-#define	ARC_L2_WRITING		(1 << 16)	/* L2ARC write in progress */
-#define	ARC_L2_EVICTED		(1 << 17)	/* evicted during I/O */
-#define	ARC_L2_WRITE_HEAD	(1 << 18)	/* head of write list */
-
-#define	HDR_IN_HASH_TABLE(hdr)	((hdr)->b_flags & ARC_IN_HASH_TABLE)
-#define	HDR_IO_IN_PROGRESS(hdr)	((hdr)->b_flags & ARC_IO_IN_PROGRESS)
-#define	HDR_IO_ERROR(hdr)	((hdr)->b_flags & ARC_IO_ERROR)
-#define	HDR_PREFETCH(hdr)	((hdr)->b_flags & ARC_PREFETCH)
-#define	HDR_FREED_IN_READ(hdr)	((hdr)->b_flags & ARC_FREED_IN_READ)
-#define	HDR_BUF_AVAILABLE(hdr)	((hdr)->b_flags & ARC_BUF_AVAILABLE)
-#define	HDR_FREE_IN_PROGRESS(hdr)	((hdr)->b_flags & ARC_FREE_IN_PROGRESS)
-#define	HDR_L2CACHE(hdr)	((hdr)->b_flags & ARC_L2CACHE)
-#define	HDR_L2_READING(hdr)	((hdr)->b_flags & ARC_IO_IN_PROGRESS &&	\
-				    (hdr)->b_l2hdr != NULL)
-#define	HDR_L2_WRITING(hdr)	((hdr)->b_flags & ARC_L2_WRITING)
-#define	HDR_L2_EVICTED(hdr)	((hdr)->b_flags & ARC_L2_EVICTED)
-#define	HDR_L2_WRITE_HEAD(hdr)	((hdr)->b_flags & ARC_L2_WRITE_HEAD)
+#define	HDR_IN_HASH_TABLE(hdr)	((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE)
+#define	HDR_IO_IN_PROGRESS(hdr)	((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS)
+#define	HDR_IO_ERROR(hdr)	((hdr)->b_flags & ARC_FLAG_IO_ERROR)
+#define	HDR_PREFETCH(hdr)	((hdr)->b_flags & ARC_FLAG_PREFETCH)
+#define	HDR_FREED_IN_READ(hdr)	((hdr)->b_flags & ARC_FLAG_FREED_IN_READ)
+#define	HDR_BUF_AVAILABLE(hdr)	((hdr)->b_flags & ARC_FLAG_BUF_AVAILABLE)
+#define	HDR_FREE_IN_PROGRESS(hdr)	\
+	((hdr)->b_flags & ARC_FLAG_FREE_IN_PROGRESS)
+#define	HDR_L2CACHE(hdr)	((hdr)->b_flags & ARC_FLAG_L2CACHE)
+#define	HDR_L2_READING(hdr)	\
+	((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS &&	\
+	    (hdr)->b_l2hdr != NULL)
+#define	HDR_L2_WRITING(hdr)	((hdr)->b_flags & ARC_FLAG_L2_WRITING)
+#define	HDR_L2_EVICTED(hdr)	((hdr)->b_flags & ARC_FLAG_L2_EVICTED)
+#define	HDR_L2_WRITE_HEAD(hdr)	((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD)
 
 /*
  * Other sizes
@@ -655,14 +631,20 @@ static kmutex_t l2arc_feed_thr_lock;
 static kcondvar_t l2arc_feed_thr_cv;
 static uint8_t l2arc_thread_exit;
 
-static void l2arc_read_done(zio_t *zio);
+static void arc_get_data_buf(arc_buf_t *);
+static void arc_access(arc_buf_hdr_t *, kmutex_t *);
+static int arc_evict_needed(arc_buf_contents_t);
+static void arc_evict_ghost(arc_state_t *, uint64_t, int64_t);
+static void arc_buf_watch(arc_buf_t *);
+
+static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *);
+static void l2arc_read_done(zio_t *);
 static void l2arc_hdr_stat_add(void);
 static void l2arc_hdr_stat_remove(void);
 
-static boolean_t l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr);
-static void l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr,
-    enum zio_compress c);
-static void l2arc_release_cdata_buf(arc_buf_hdr_t *ab);
+static boolean_t l2arc_compress_buf(l2arc_buf_hdr_t *);
+static void l2arc_decompress_zio(zio_t *, arc_buf_hdr_t *, enum zio_compress);
+static void l2arc_release_cdata_buf(arc_buf_hdr_t *);
 
 static uint64_t
 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
@@ -707,14 +689,14 @@ buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
 	uint64_t birth = BP_PHYSICAL_BIRTH(bp);
 	uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
 	kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
-	arc_buf_hdr_t *buf;
+	arc_buf_hdr_t *hdr;
 
 	mutex_enter(hash_lock);
-	for (buf = buf_hash_table.ht_table[idx]; buf != NULL;
-	    buf = buf->b_hash_next) {
-		if (BUF_EQUAL(spa, dva, birth, buf)) {
+	for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL;
+	    hdr = hdr->b_hash_next) {
+		if (BUF_EQUAL(spa, dva, birth, hdr)) {
 			*lockp = hash_lock;
-			return (buf);
+			return (hdr);
 		}
 	}
 	mutex_exit(hash_lock);
@@ -729,27 +711,27 @@ buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
  * Otherwise returns NULL.
  */
 static arc_buf_hdr_t *
-buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp)
+buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp)
 {
-	uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
+	uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
 	kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
-	arc_buf_hdr_t *fbuf;
+	arc_buf_hdr_t *fhdr;
 	uint32_t i;
 
-	ASSERT(!DVA_IS_EMPTY(&buf->b_dva));
-	ASSERT(buf->b_birth != 0);
-	ASSERT(!HDR_IN_HASH_TABLE(buf));
+	ASSERT(!DVA_IS_EMPTY(&hdr->b_dva));
+	ASSERT(hdr->b_birth != 0);
+	ASSERT(!HDR_IN_HASH_TABLE(hdr));
 	*lockp = hash_lock;
 	mutex_enter(hash_lock);
-	for (fbuf = buf_hash_table.ht_table[idx], i = 0; fbuf != NULL;
-	    fbuf = fbuf->b_hash_next, i++) {
-		if (BUF_EQUAL(buf->b_spa, &buf->b_dva, buf->b_birth, fbuf))
-			return (fbuf);
+	for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL;
+	    fhdr = fhdr->b_hash_next, i++) {
+		if (BUF_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr))
+			return (fhdr);
 	}
 
-	buf->b_hash_next = buf_hash_table.ht_table[idx];
-	buf_hash_table.ht_table[idx] = buf;
-	buf->b_flags |= ARC_IN_HASH_TABLE;
+	hdr->b_hash_next = buf_hash_table.ht_table[idx];
+	buf_hash_table.ht_table[idx] = hdr;
+	hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE;
 
 	/* collect some hash table performance data */
 	if (i > 0) {
@@ -767,22 +749,22 @@ buf_hash_insert(arc_buf_hdr_t *buf, kmutex_t **lockp)
 }
 
 static void
-buf_hash_remove(arc_buf_hdr_t *buf)
+buf_hash_remove(arc_buf_hdr_t *hdr)
 {
-	arc_buf_hdr_t *fbuf, **bufp;
-	uint64_t idx = BUF_HASH_INDEX(buf->b_spa, &buf->b_dva, buf->b_birth);
+	arc_buf_hdr_t *fhdr, **hdrp;
+	uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
 
 	ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
-	ASSERT(HDR_IN_HASH_TABLE(buf));
+	ASSERT(HDR_IN_HASH_TABLE(hdr));
 
-	bufp = &buf_hash_table.ht_table[idx];
-	while ((fbuf = *bufp) != buf) {
-		ASSERT(fbuf != NULL);
-		bufp = &fbuf->b_hash_next;
+	hdrp = &buf_hash_table.ht_table[idx];
+	while ((fhdr = *hdrp) != hdr) {
+		ASSERT(fhdr != NULL);
+		hdrp = &fhdr->b_hash_next;
 	}
-	*bufp = buf->b_hash_next;
-	buf->b_hash_next = NULL;
-	buf->b_flags &= ~ARC_IN_HASH_TABLE;
+	*hdrp = hdr->b_hash_next;
+	hdr->b_hash_next = NULL;
+	hdr->b_flags &= ~ARC_FLAG_IN_HASH_TABLE;
 
 	/* collect some hash table performance data */
 	ARCSTAT_BUMPDOWN(arcstat_hash_elements);
@@ -828,14 +810,14 @@ buf_fini(void)
 static int
 hdr_cons(void *vbuf, void *unused, int kmflag)
 {
-	arc_buf_hdr_t *buf = vbuf;
-
-	bzero(buf, sizeof (arc_buf_hdr_t));
-	refcount_create(&buf->b_refcnt);
-	cv_init(&buf->b_cv, NULL, CV_DEFAULT, NULL);
-	mutex_init(&buf->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
-	list_link_init(&buf->b_arc_node);
-	list_link_init(&buf->b_l2node);
+	arc_buf_hdr_t *hdr = vbuf;
+
+	bzero(hdr, sizeof (arc_buf_hdr_t));
+	refcount_create(&hdr->b_refcnt);
+	cv_init(&hdr->b_cv, NULL, CV_DEFAULT, NULL);
+	mutex_init(&hdr->b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
+	list_link_init(&hdr->b_arc_node);
+	list_link_init(&hdr->b_l2node);
 	arc_space_consume(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
 
 	return (0);
@@ -862,12 +844,12 @@ buf_cons(void *vbuf, void *unused, int kmflag)
 static void
 hdr_dest(void *vbuf, void *unused)
 {
-	arc_buf_hdr_t *buf = vbuf;
+	arc_buf_hdr_t *hdr = vbuf;
 
-	ASSERT(BUF_EMPTY(buf));
-	refcount_destroy(&buf->b_refcnt);
-	cv_destroy(&buf->b_cv);
-	mutex_destroy(&buf->b_freeze_lock);
+	ASSERT(BUF_EMPTY(hdr));
+	refcount_destroy(&hdr->b_refcnt);
+	cv_destroy(&hdr->b_cv);
+	mutex_destroy(&hdr->b_freeze_lock);
 	arc_space_return(sizeof (arc_buf_hdr_t), ARC_SPACE_HDRS);
 }
 
@@ -942,7 +924,7 @@ arc_cksum_verify(arc_buf_t *buf)
 
 	mutex_enter(&buf->b_hdr->b_freeze_lock);
 	if (buf->b_hdr->b_freeze_cksum == NULL ||
-	    (buf->b_hdr->b_flags & ARC_IO_ERROR)) {
+	    (buf->b_hdr->b_flags & ARC_FLAG_IO_ERROR)) {
 		mutex_exit(&buf->b_hdr->b_freeze_lock);
 		return;
 	}
@@ -1021,7 +1003,7 @@ arc_buf_thaw(arc_buf_t *buf)
 	if (zfs_flags & ZFS_DEBUG_MODIFY) {
 		if (buf->b_hdr->b_state != arc_anon)
 			panic("modifying non-anon buffer!");
-		if (buf->b_hdr->b_flags & ARC_IO_IN_PROGRESS)
+		if (buf->b_hdr->b_flags & ARC_FLAG_IO_IN_PROGRESS)
 			panic("modifying buffer while i/o in progress!");
 		arc_cksum_verify(buf);
 	}
@@ -1056,54 +1038,54 @@ arc_buf_freeze(arc_buf_t *buf)
 }
 
 static void
-add_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
+add_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag)
 {
 	ASSERT(MUTEX_HELD(hash_lock));
 
-	if ((refcount_add(&ab->b_refcnt, tag) == 1) &&
-	    (ab->b_state != arc_anon)) {
-		uint64_t delta = ab->b_size * ab->b_datacnt;
-		list_t *list = &ab->b_state->arcs_list[ab->b_type];
-		uint64_t *size = &ab->b_state->arcs_lsize[ab->b_type];
-
-		ASSERT(!MUTEX_HELD(&ab->b_state->arcs_mtx));
-		mutex_enter(&ab->b_state->arcs_mtx);
-		ASSERT(list_link_active(&ab->b_arc_node));
-		list_remove(list, ab);
-		if (GHOST_STATE(ab->b_state)) {
-			ASSERT0(ab->b_datacnt);
-			ASSERT3P(ab->b_buf, ==, NULL);
-			delta = ab->b_size;
+	if ((refcount_add(&hdr->b_refcnt, tag) == 1) &&
+	    (hdr->b_state != arc_anon)) {
+		uint64_t delta = hdr->b_size * hdr->b_datacnt;
+		list_t *list = &hdr->b_state->arcs_list[hdr->b_type];
+		uint64_t *size = &hdr->b_state->arcs_lsize[hdr->b_type];
+
+		ASSERT(!MUTEX_HELD(&hdr->b_state->arcs_mtx));
+		mutex_enter(&hdr->b_state->arcs_mtx);
+		ASSERT(list_link_active(&hdr->b_arc_node));
+		list_remove(list, hdr);
+		if (GHOST_STATE(hdr->b_state)) {
+			ASSERT0(hdr->b_datacnt);
+			ASSERT3P(hdr->b_buf, ==, NULL);
+			delta = hdr->b_size;
 		}
 		ASSERT(delta > 0);
 		ASSERT3U(*size, >=, delta);
 		atomic_add_64(size, -delta);
-		mutex_exit(&ab->b_state->arcs_mtx);
+		mutex_exit(&hdr->b_state->arcs_mtx);
 		/* remove the prefetch flag if we get a reference */
-		if (ab->b_flags & ARC_PREFETCH)
-			ab->b_flags &= ~ARC_PREFETCH;
+		if (hdr->b_flags & ARC_FLAG_PREFETCH)
+			hdr->b_flags &= ~ARC_FLAG_PREFETCH;
 	}
 }
 
 static int
-remove_reference(arc_buf_hdr_t *ab, kmutex_t *hash_lock, void *tag)
+remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag)
 {
 	int cnt;
-	arc_state_t *state = ab->b_state;
+	arc_state_t *state = hdr->b_state;
 
 	ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
 	ASSERT(!GHOST_STATE(state));
 
-	if (((cnt = refcount_remove(&ab->b_refcnt, tag)) == 0) &&
+	if (((cnt = refcount_remove(&hdr->b_refcnt, tag)) == 0) &&
 	    (state != arc_anon)) {
-		uint64_t *size = &state->arcs_lsize[ab->b_type];
+		uint64_t *size = &state->arcs_lsize[hdr->b_type];
 
 		ASSERT(!MUTEX_HELD(&state->arcs_mtx));
 		mutex_enter(&state->arcs_mtx);
-		ASSERT(!list_link_active(&ab->b_arc_node));
-		list_insert_head(&state->arcs_list[ab->b_type], ab);
-		ASSERT(ab->b_datacnt > 0);
-		atomic_add_64(size, ab->b_size * ab->b_datacnt);
+		ASSERT(!list_link_active(&hdr->b_arc_node));
+		list_insert_head(&state->arcs_list[hdr->b_type], hdr);
+		ASSERT(hdr->b_datacnt > 0);
+		atomic_add_64(size, hdr->b_size * hdr->b_datacnt);
 		mutex_exit(&state->arcs_mtx);
 	}
 	return (cnt);
@@ -1162,19 +1144,20 @@ arc_buf_info(arc_buf_t *ab, arc_buf_info_t *abi, int state_index)
  * for the buffer must be held by the caller.
  */
 static void
-arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
+arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr,
+    kmutex_t *hash_lock)
 {
-	arc_state_t *old_state = ab->b_state;
-	int64_t refcnt = refcount_count(&ab->b_refcnt);
+	arc_state_t *old_state = hdr->b_state;
+	int64_t refcnt = refcount_count(&hdr->b_refcnt);
 	uint64_t from_delta, to_delta;
 
 	ASSERT(MUTEX_HELD(hash_lock));
 	ASSERT3P(new_state, !=, old_state);
-	ASSERT(refcnt == 0 || ab->b_datacnt > 0);
-	ASSERT(ab->b_datacnt == 0 || !GHOST_STATE(new_state));
-	ASSERT(ab->b_datacnt <= 1 || old_state != arc_anon);
+	ASSERT(refcnt == 0 || hdr->b_datacnt > 0);
+	ASSERT(hdr->b_datacnt == 0 || !GHOST_STATE(new_state));
+	ASSERT(hdr->b_datacnt <= 1 || old_state != arc_anon);
 
-	from_delta = to_delta = ab->b_datacnt * ab->b_size;
+	from_delta = to_delta = hdr->b_datacnt * hdr->b_size;
 
 	/*
 	 * If this buffer is evictable, transfer it from the
@@ -1183,22 +1166,22 @@ arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
 	if (refcnt == 0) {
 		if (old_state != arc_anon) {
 			int use_mutex = !MUTEX_HELD(&old_state->arcs_mtx);
-			uint64_t *size = &old_state->arcs_lsize[ab->b_type];
+			uint64_t *size = &old_state->arcs_lsize[hdr->b_type];
 
 			if (use_mutex)
 				mutex_enter(&old_state->arcs_mtx);
 
-			ASSERT(list_link_active(&ab->b_arc_node));
-			list_remove(&old_state->arcs_list[ab->b_type], ab);
+			ASSERT(list_link_active(&hdr->b_arc_node));
+			list_remove(&old_state->arcs_list[hdr->b_type], hdr);
 
 			/*
 			 * If prefetching out of the ghost cache,
 			 * we will have a non-zero datacnt.
 			 */
-			if (GHOST_STATE(old_state) && ab->b_datacnt == 0) {
+			if (GHOST_STATE(old_state) && hdr->b_datacnt == 0) {
 				/* ghost elements have a ghost size */
-				ASSERT(ab->b_buf == NULL);
-				from_delta = ab->b_size;
+				ASSERT(hdr->b_buf == NULL);
+				from_delta = hdr->b_size;
 			}
 			ASSERT3U(*size, >=, from_delta);
 			atomic_add_64(size, -from_delta);
@@ -1208,18 +1191,19 @@ arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
 		}
 		if (new_state != arc_anon) {
 			int use_mutex = !MUTEX_HELD(&new_state->arcs_mtx);
-			uint64_t *size = &new_state->arcs_lsize[ab->b_type];
+			uint64_t *size = &new_state->arcs_lsize[hdr->b_type];
 
 			if (use_mutex)
 				mutex_enter(&new_state->arcs_mtx);
 
-			list_insert_head(&new_state->arcs_list[ab->b_type], ab);
+			list_insert_head(&new_state->arcs_list[hdr->b_type],
+			    hdr);
 
 			/* ghost elements have a ghost size */
 			if (GHOST_STATE(new_state)) {
-				ASSERT(ab->b_datacnt == 0);
-				ASSERT(ab->b_buf == NULL);
-				to_delta = ab->b_size;
+				ASSERT(hdr->b_datacnt == 0);
+				ASSERT(hdr->b_buf == NULL);
+				to_delta = hdr->b_size;
 			}
 			atomic_add_64(size, to_delta);
 
@@ -1228,9 +1212,9 @@ arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
 		}
 	}
 
-	ASSERT(!BUF_EMPTY(ab));
-	if (new_state == arc_anon && HDR_IN_HASH_TABLE(ab))
-		buf_hash_remove(ab);
+	ASSERT(!BUF_EMPTY(hdr));
+	if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr))
+		buf_hash_remove(hdr);
 
 	/* adjust state sizes */
 	if (to_delta)
@@ -1239,7 +1223,7 @@ arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *ab, kmutex_t *hash_lock)
 		ASSERT3U(old_state->arcs_size, >=, from_delta);
 		atomic_add_64(&old_state->arcs_size, -from_delta);
 	}
-	ab->b_state = new_state;
+	hdr->b_state = new_state;
 
 	/* adjust l2arc hdr stats */
 	if (new_state == arc_l2c_only)
@@ -1462,7 +1446,7 @@ arc_buf_add_ref(arc_buf_t *buf, void* tag)
 	arc_access(hdr, hash_lock);
 	mutex_exit(hash_lock);
 	ARCSTAT_BUMP(arcstat_hits);
-	ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
+	ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_FLAG_PREFETCH),
 	    demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
 	    data, metadata, hits);
 }
@@ -1660,7 +1644,7 @@ arc_buf_free(arc_buf_t *buf, void *tag)
 		} else {
 			ASSERT(buf == hdr->b_buf);
 			ASSERT(buf->b_efunc == NULL);
-			hdr->b_flags |= ARC_BUF_AVAILABLE;
+			hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE;
 		}
 		mutex_exit(hash_lock);
 	} else if (HDR_IO_IN_PROGRESS(hdr)) {
@@ -1712,7 +1696,7 @@ arc_buf_remove_ref(arc_buf_t *buf, void* tag)
 	} else if (no_callback) {
 		ASSERT(hdr->b_buf == buf && buf->b_next == NULL);
 		ASSERT(buf->b_efunc == NULL);
-		hdr->b_flags |= ARC_BUF_AVAILABLE;
+		hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE;
 	}
 	ASSERT(no_callback || hdr->b_datacnt > 1 ||
 	    refcount_is_zero(&hdr->b_refcnt));
@@ -1787,7 +1771,7 @@ arc_evict(arc_state_t *state, uint64_t spa, int64_t bytes, boolean_t recycle,
 {
 	arc_state_t *evicted_state;
 	uint64_t bytes_evicted = 0, skipped = 0, missed = 0;
-	arc_buf_hdr_t *ab, *ab_prev = NULL;
+	arc_buf_hdr_t *hdr, *hdr_prev = NULL;
 	list_t *list = &state->arcs_list[type];
 	kmutex_t *hash_lock;
 	boolean_t have_lock;
@@ -1803,24 +1787,24 @@ top:
 	mutex_enter(&state->arcs_mtx);
 	mutex_enter(&evicted_state->arcs_mtx);
 
-	for (ab = list_tail(list); ab; ab = ab_prev) {
-		ab_prev = list_prev(list, ab);
+	for (hdr = list_tail(list); hdr; hdr = hdr_prev) {
+		hdr_prev = list_prev(list, hdr);
 		/* prefetch buffers have a minimum lifespan */
-		if (HDR_IO_IN_PROGRESS(ab) ||
-		    (spa && ab->b_spa != spa) ||
-		    (ab->b_flags & (ARC_PREFETCH|ARC_INDIRECT) &&
-		    ddi_get_lbolt() - ab->b_arc_access <
+		if (HDR_IO_IN_PROGRESS(hdr) ||
+		    (spa && hdr->b_spa != spa) ||
+		    (hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT) &&
+		    ddi_get_lbolt() - hdr->b_arc_access <
 		    zfs_arc_min_prefetch_lifespan)) {
 			skipped++;
 			continue;
 		}
 		/* "lookahead" for better eviction candidate */
-		if (recycle && ab->b_size != bytes &&
-		    ab_prev && ab_prev->b_size == bytes)
+		if (recycle && hdr->b_size != bytes &&
+		    hdr_prev && hdr_prev->b_size == bytes)
 			continue;
 
 		/* ignore markers */
-		if (ab->b_spa == 0)
+		if (hdr->b_spa == 0)
 			continue;
 
 		/*
@@ -1833,34 +1817,34 @@ top:
 		 * the hot code path, so don't sleep.
 		 */
 		if (!recycle && count++ > arc_evict_iterations) {
-			list_insert_after(list, ab, &marker);
+			list_insert_after(list, hdr, &marker);
 			mutex_exit(&evicted_state->arcs_mtx);
 			mutex_exit(&state->arcs_mtx);
 			kpreempt(KPREEMPT_SYNC);
 			mutex_enter(&state->arcs_mtx);
 			mutex_enter(&evicted_state->arcs_mtx);
-			ab_prev = list_prev(list, &marker);
+			hdr_prev = list_prev(list, &marker);
 			list_remove(list, &marker);
 			count = 0;
 			continue;
 		}
 
-		hash_lock = HDR_LOCK(ab);
+		hash_lock = HDR_LOCK(hdr);
 		have_lock = MUTEX_HELD(hash_lock);
 		if (have_lock || mutex_tryenter(hash_lock)) {
-			ASSERT0(refcount_count(&ab->b_refcnt));
-			ASSERT(ab->b_datacnt > 0);
-			while (ab->b_buf) {
-				arc_buf_t *buf = ab->b_buf;
+			ASSERT0(refcount_count(&hdr->b_refcnt));
+			ASSERT(hdr->b_datacnt > 0);
+			while (hdr->b_buf) {
+				arc_buf_t *buf = hdr->b_buf;
 				if (!mutex_tryenter(&buf->b_evict_lock)) {
 					missed += 1;
 					break;
 				}
 				if (buf->b_data) {
-					bytes_evicted += ab->b_size;
-					if (recycle && ab->b_type == type &&
-					    ab->b_size == bytes &&
-					    !HDR_L2_WRITING(ab)) {
+					bytes_evicted += hdr->b_size;
+					if (recycle && hdr->b_type == type &&
+					    hdr->b_size == bytes &&
+					    !HDR_L2_WRITING(hdr)) {
 						stolen = buf->b_data;
 						recycle = FALSE;
 					}
@@ -1869,7 +1853,7 @@ top:
 					mutex_enter(&arc_eviction_mtx);
 					arc_buf_destroy(buf,
 					    buf->b_data == stolen, FALSE);
-					ab->b_buf = buf->b_next;
+					hdr->b_buf = buf->b_next;
 					buf->b_hdr = &arc_eviction_hdr;
 					buf->b_next = arc_eviction_list;
 					arc_eviction_list = buf;
@@ -1882,26 +1866,26 @@ top:
 				}
 			}
 
-			if (ab->b_l2hdr) {
+			if (hdr->b_l2hdr) {
 				ARCSTAT_INCR(arcstat_evict_l2_cached,
-				    ab->b_size);
+				    hdr->b_size);
 			} else {
-				if (l2arc_write_eligible(ab->b_spa, ab)) {
+				if (l2arc_write_eligible(hdr->b_spa, hdr)) {
 					ARCSTAT_INCR(arcstat_evict_l2_eligible,
-					    ab->b_size);
+					    hdr->b_size);
 				} else {
 					ARCSTAT_INCR(
 					    arcstat_evict_l2_ineligible,
-					    ab->b_size);
+					    hdr->b_size);
 				}
 			}
 
-			if (ab->b_datacnt == 0) {
-				arc_change_state(evicted_state, ab, hash_lock);
-				ASSERT(HDR_IN_HASH_TABLE(ab));
-				ab->b_flags |= ARC_IN_HASH_TABLE;
-				ab->b_flags &= ~ARC_BUF_AVAILABLE;
-				DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, ab);
+			if (hdr->b_datacnt == 0) {
+				arc_change_state(evicted_state, hdr, hash_lock);
+				ASSERT(HDR_IN_HASH_TABLE(hdr));
+				hdr->b_flags |= ARC_FLAG_IN_HASH_TABLE;
+				hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE;
+				DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr);
 			}
 			if (!have_lock)
 				mutex_exit(hash_lock);
@@ -1950,7 +1934,7 @@ top:
 static void
 arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes)
 {
-	arc_buf_hdr_t *ab, *ab_prev;
+	arc_buf_hdr_t *hdr, *hdr_prev;
 	arc_buf_hdr_t marker;
 	list_t *list = &state->arcs_list[ARC_BUFC_DATA];
 	kmutex_t *hash_lock;
@@ -1962,18 +1946,18 @@ arc_evict_ghost(arc_state_t *state, uint64_t spa, int64_t bytes)
 	bzero(&marker, sizeof (marker));
 top:
 	mutex_enter(&state->arcs_mtx);
-	for (ab = list_tail(list); ab; ab = ab_prev) {
-		ab_prev = list_prev(list, ab);
-		if (ab->b_type > ARC_BUFC_NUMTYPES)
-			panic("invalid ab=%p", (void *)ab);
-		if (spa && ab->b_spa != spa)
+	for (hdr = list_tail(list); hdr; hdr = hdr_prev) {
+		hdr_prev = list_prev(list, hdr);
+		if (hdr->b_type > ARC_BUFC_NUMTYPES)
+			panic("invalid hdr=%p", (void *)hdr);
+		if (spa && hdr->b_spa != spa)
 			continue;
 
 		/* ignore markers */
-		if (ab->b_spa == 0)
+		if (hdr->b_spa == 0)
 			continue;
 
-		hash_lock = HDR_LOCK(ab);
+		hash_lock = HDR_LOCK(hdr);
 		/* caller may be trying to modify this buffer, skip it */
 		if (MUTEX_HELD(hash_lock))
 			continue;
@@ -1985,35 +1969,35 @@ top:
 		 * before reacquiring the lock.
 		 */
 		if (count++ > arc_evict_iterations) {
-			list_insert_after(list, ab, &marker);
+			list_insert_after(list, hdr, &marker);
 			mutex_exit(&state->arcs_mtx);
 			kpreempt(KPREEMPT_SYNC);
 			mutex_enter(&state->arcs_mtx);
-			ab_prev = list_prev(list, &marker);
+			hdr_prev = list_prev(list, &marker);
 			list_remove(list, &marker);
 			count = 0;
 			continue;
 		}
 		if (mutex_tryenter(hash_lock)) {
-			ASSERT(!HDR_IO_IN_PROGRESS(ab));
-			ASSERT(ab->b_buf == NULL);
+			ASSERT(!HDR_IO_IN_PROGRESS(hdr));
+			ASSERT(hdr->b_buf == NULL);
 			ARCSTAT_BUMP(arcstat_deleted);
-			bytes_deleted += ab->b_size;
+			bytes_deleted += hdr->b_size;
 
-			if (ab->b_l2hdr != NULL) {
+			if (hdr->b_l2hdr != NULL) {
 				/*
 				 * This buffer is cached on the 2nd Level ARC;
 				 * don't destroy the header.
 				 */
-				arc_change_state(arc_l2c_only, ab, hash_lock);
+				arc_change_state(arc_l2c_only, hdr, hash_lock);
 				mutex_exit(hash_lock);
 			} else {
-				arc_change_state(arc_anon, ab, hash_lock);
+				arc_change_state(arc_anon, hdr, hash_lock);
 				mutex_exit(hash_lock);
-				arc_hdr_destroy(ab);
+				arc_hdr_destroy(hdr);
 			}
 
-			DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, ab);
+			DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr);
 			if (bytes >= 0 && bytes_deleted >= bytes)
 				break;
 		} else if (bytes < 0) {
@@ -2022,12 +2006,12 @@ top:
 			 * hash lock to become available. Once its
 			 * available, restart from where we left off.
 			 */
-			list_insert_after(list, ab, &marker);
+			list_insert_after(list, hdr, &marker);
 			mutex_exit(&state->arcs_mtx);
 			mutex_enter(hash_lock);
 			mutex_exit(hash_lock);
 			mutex_enter(&state->arcs_mtx);
-			ab_prev = list_prev(list, &marker);
+			hdr_prev = list_prev(list, &marker);
 			list_remove(list, &marker);
 		} else {
 			bufs_skipped += 1;
@@ -2734,7 +2718,8 @@ arc_get_data_buf(arc_buf_t *buf)
 	 * will end up on the mru list; so steal space from there.
 	 */
 	if (state == arc_mfu_ghost)
-		state = buf->b_hdr->b_flags & ARC_PREFETCH ? arc_mru : arc_mfu;
+		state = buf->b_hdr->b_flags & ARC_FLAG_PREFETCH ?
+		    arc_mru : arc_mfu;
 	else if (state == arc_mru_ghost)
 		state = arc_mru;
 
@@ -2821,25 +2806,25 @@ out:
  * NOTE: the hash lock is dropped in this function.
  */
 static void
-arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
+arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
 {
 	clock_t now;
 
 	ASSERT(MUTEX_HELD(hash_lock));
 
-	if (buf->b_state == arc_anon) {
+	if (hdr->b_state == arc_anon) {
 		/*
 		 * This buffer is not in the cache, and does not
 		 * appear in our "ghost" list.  Add the new buffer
 		 * to the MRU state.
 		 */
 
-		ASSERT(buf->b_arc_access == 0);
-		buf->b_arc_access = ddi_get_lbolt();
-		DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
-		arc_change_state(arc_mru, buf, hash_lock);
+		ASSERT(hdr->b_arc_access == 0);
+		hdr->b_arc_access = ddi_get_lbolt();
+		DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
+		arc_change_state(arc_mru, hdr, hash_lock);
 
-	} else if (buf->b_state == arc_mru) {
+	} else if (hdr->b_state == arc_mru) {
 		now = ddi_get_lbolt();
 
 		/*
@@ -2850,15 +2835,15 @@ arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
 		 * - move the buffer to the head of the list if this is
 		 *   another prefetch (to make it less likely to be evicted).
 		 */
-		if ((buf->b_flags & ARC_PREFETCH) != 0) {
-			if (refcount_count(&buf->b_refcnt) == 0) {
-				ASSERT(list_link_active(&buf->b_arc_node));
+		if ((hdr->b_flags & ARC_FLAG_PREFETCH) != 0) {
+			if (refcount_count(&hdr->b_refcnt) == 0) {
+				ASSERT(list_link_active(&hdr->b_arc_node));
 			} else {
-				buf->b_flags &= ~ARC_PREFETCH;
-				atomic_inc_32(&buf->b_mru_hits);
+				hdr->b_flags &= ~ARC_FLAG_PREFETCH;
+				atomic_inc_32(&hdr->b_mru_hits);
 				ARCSTAT_BUMP(arcstat_mru_hits);
 			}
-			buf->b_arc_access = now;
+			hdr->b_arc_access = now;
 			return;
 		}
 
@@ -2867,19 +2852,19 @@ arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
 		 * but it is still in the cache. Move it to the MFU
 		 * state.
 		 */
-		if (ddi_time_after(now, buf->b_arc_access + ARC_MINTIME)) {
+		if (ddi_time_after(now, hdr->b_arc_access + ARC_MINTIME)) {
 			/*
 			 * More than 125ms have passed since we
 			 * instantiated this buffer.  Move it to the
 			 * most frequently used state.
 			 */
-			buf->b_arc_access = now;
-			DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
-			arc_change_state(arc_mfu, buf, hash_lock);
+			hdr->b_arc_access = now;
+			DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
+			arc_change_state(arc_mfu, hdr, hash_lock);
 		}
-		atomic_inc_32(&buf->b_mru_hits);
+		atomic_inc_32(&hdr->b_mru_hits);
 		ARCSTAT_BUMP(arcstat_mru_hits);
-	} else if (buf->b_state == arc_mru_ghost) {
+	} else if (hdr->b_state == arc_mru_ghost) {
 		arc_state_t	*new_state;
 		/*
 		 * This buffer has been "accessed" recently, but
@@ -2887,22 +2872,22 @@ arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
 		 * MFU state.
 		 */
 
-		if (buf->b_flags & ARC_PREFETCH) {
+		if (hdr->b_flags & ARC_FLAG_PREFETCH) {
 			new_state = arc_mru;
-			if (refcount_count(&buf->b_refcnt) > 0)
-				buf->b_flags &= ~ARC_PREFETCH;
-			DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, buf);
+			if (refcount_count(&hdr->b_refcnt) > 0)
+				hdr->b_flags &= ~ARC_FLAG_PREFETCH;
+			DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
 		} else {
 			new_state = arc_mfu;
-			DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
+			DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
 		}
 
-		buf->b_arc_access = ddi_get_lbolt();
-		arc_change_state(new_state, buf, hash_lock);
+		hdr->b_arc_access = ddi_get_lbolt();
+		arc_change_state(new_state, hdr, hash_lock);
 
-		atomic_inc_32(&buf->b_mru_ghost_hits);
+		atomic_inc_32(&hdr->b_mru_ghost_hits);
 		ARCSTAT_BUMP(arcstat_mru_ghost_hits);
-	} else if (buf->b_state == arc_mfu) {
+	} else if (hdr->b_state == arc_mfu) {
 		/*
 		 * This buffer has been accessed more than once and is
 		 * still in the cache.  Keep it in the MFU state.
@@ -2912,14 +2897,14 @@ arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
 		 * If it was a prefetch, we will explicitly move it to
 		 * the head of the list now.
 		 */
-		if ((buf->b_flags & ARC_PREFETCH) != 0) {
-			ASSERT(refcount_count(&buf->b_refcnt) == 0);
-			ASSERT(list_link_active(&buf->b_arc_node));
+		if ((hdr->b_flags & ARC_FLAG_PREFETCH) != 0) {
+			ASSERT(refcount_count(&hdr->b_refcnt) == 0);
+			ASSERT(list_link_active(&hdr->b_arc_node));
 		}
-		atomic_inc_32(&buf->b_mfu_hits);
+		atomic_inc_32(&hdr->b_mfu_hits);
 		ARCSTAT_BUMP(arcstat_mfu_hits);
-		buf->b_arc_access = ddi_get_lbolt();
-	} else if (buf->b_state == arc_mfu_ghost) {
+		hdr->b_arc_access = ddi_get_lbolt();
+	} else if (hdr->b_state == arc_mfu_ghost) {
 		arc_state_t	*new_state = arc_mfu;
 		/*
 		 * This buffer has been accessed more than once but has
@@ -2927,31 +2912,31 @@ arc_access(arc_buf_hdr_t *buf, kmutex_t *hash_lock)
 		 * MFU state.
 		 */
 
-		if (buf->b_flags & ARC_PREFETCH) {
+		if (hdr->b_flags & ARC_FLAG_PREFETCH) {
 			/*
 			 * This is a prefetch access...
 			 * move this block back to the MRU state.
 			 */
-			ASSERT0(refcount_count(&buf->b_refcnt));
+			ASSERT0(refcount_count(&hdr->b_refcnt));
 			new_state = arc_mru;
 		}
 
-		buf->b_arc_access = ddi_get_lbolt();
-		DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
-		arc_change_state(new_state, buf, hash_lock);
+		hdr->b_arc_access = ddi_get_lbolt();
+		DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
+		arc_change_state(new_state, hdr, hash_lock);
 
-		atomic_inc_32(&buf->b_mfu_ghost_hits);
+		atomic_inc_32(&hdr->b_mfu_ghost_hits);
 		ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
-	} else if (buf->b_state == arc_l2c_only) {
+	} else if (hdr->b_state == arc_l2c_only) {
 		/*
 		 * This buffer is on the 2nd Level ARC.
 		 */
 
-		buf->b_arc_access = ddi_get_lbolt();
-		DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, buf);
-		arc_change_state(arc_mfu, buf, hash_lock);
+		hdr->b_arc_access = ddi_get_lbolt();
+		DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
+		arc_change_state(arc_mfu, hdr, hash_lock);
 	} else {
-		cmn_err(CE_PANIC, "invalid arc state 0x%p", buf->b_state);
+		cmn_err(CE_PANIC, "invalid arc state 0x%p", hdr->b_state);
 	}
 }
 
@@ -3019,9 +3004,9 @@ arc_read_done(zio_t *zio)
 		    (found == hdr && HDR_L2_READING(hdr)));
 	}
 
-	hdr->b_flags &= ~ARC_L2_EVICTED;
-	if (l2arc_noprefetch && (hdr->b_flags & ARC_PREFETCH))
-		hdr->b_flags &= ~ARC_L2CACHE;
+	hdr->b_flags &= ~ARC_FLAG_L2_EVICTED;
+	if (l2arc_noprefetch && (hdr->b_flags & ARC_FLAG_PREFETCH))
+		hdr->b_flags &= ~ARC_FLAG_L2CACHE;
 
 	/* byteswap if necessary */
 	callback_list = hdr->b_acb;
@@ -3061,18 +3046,18 @@ arc_read_done(zio_t *zio)
 		}
 	}
 	hdr->b_acb = NULL;
-	hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
+	hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS;
 	ASSERT(!HDR_BUF_AVAILABLE(hdr));
 	if (abuf == buf) {
 		ASSERT(buf->b_efunc == NULL);
 		ASSERT(hdr->b_datacnt == 1);
-		hdr->b_flags |= ARC_BUF_AVAILABLE;
+		hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE;
 	}
 
 	ASSERT(refcount_is_zero(&hdr->b_refcnt) || callback_list != NULL);
 
 	if (zio->io_error != 0) {
-		hdr->b_flags |= ARC_IO_ERROR;
+		hdr->b_flags |= ARC_FLAG_IO_ERROR;
 		if (hdr->b_state != arc_anon)
 			arc_change_state(arc_anon, hdr, hash_lock);
 		if (HDR_IN_HASH_TABLE(hdr))
@@ -3138,8 +3123,8 @@ arc_read_done(zio_t *zio)
  */
 int
 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_done_func_t *done,
-    void *private, zio_priority_t priority, int zio_flags, uint32_t *arc_flags,
-    const zbookmark_phys_t *zb)
+    void *private, zio_priority_t priority, int zio_flags,
+    arc_flags_t *arc_flags, const zbookmark_phys_t *zb)
 {
 	arc_buf_hdr_t *hdr = NULL;
 	arc_buf_t *buf = NULL;
@@ -3162,16 +3147,16 @@ top:
 
 	if (hdr != NULL && hdr->b_datacnt > 0) {
 
-		*arc_flags |= ARC_CACHED;
+		*arc_flags |= ARC_FLAG_CACHED;
 
 		if (HDR_IO_IN_PROGRESS(hdr)) {
 
-			if (*arc_flags & ARC_WAIT) {
+			if (*arc_flags & ARC_FLAG_WAIT) {
 				cv_wait(&hdr->b_cv, hash_lock);
 				mutex_exit(hash_lock);
 				goto top;
 			}
-			ASSERT(*arc_flags & ARC_NOWAIT);
+			ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
 
 			if (done) {
 				arc_callback_t	*acb = NULL;
@@ -3209,24 +3194,24 @@ top:
 			ASSERT(buf->b_data);
 			if (HDR_BUF_AVAILABLE(hdr)) {
 				ASSERT(buf->b_efunc == NULL);
-				hdr->b_flags &= ~ARC_BUF_AVAILABLE;
+				hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE;
 			} else {
 				buf = arc_buf_clone(buf);
 			}
 
-		} else if (*arc_flags & ARC_PREFETCH &&
+		} else if (*arc_flags & ARC_FLAG_PREFETCH &&
 		    refcount_count(&hdr->b_refcnt) == 0) {
-			hdr->b_flags |= ARC_PREFETCH;
+			hdr->b_flags |= ARC_FLAG_PREFETCH;
 		}
 		DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
 		arc_access(hdr, hash_lock);
-		if (*arc_flags & ARC_L2CACHE)
-			hdr->b_flags |= ARC_L2CACHE;
-		if (*arc_flags & ARC_L2COMPRESS)
-			hdr->b_flags |= ARC_L2COMPRESS;
+		if (*arc_flags & ARC_FLAG_L2CACHE)
+			hdr->b_flags |= ARC_FLAG_L2CACHE;
+		if (*arc_flags & ARC_FLAG_L2COMPRESS)
+			hdr->b_flags |= ARC_FLAG_L2COMPRESS;
 		mutex_exit(hash_lock);
 		ARCSTAT_BUMP(arcstat_hits);
-		ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
+		ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_FLAG_PREFETCH),
 		    demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
 		    data, metadata, hits);
 
@@ -3276,18 +3261,19 @@ top:
 				(void) arc_buf_remove_ref(buf, private);
 				goto top; /* restart the IO request */
 			}
+
 			/* if this is a prefetch, we don't have a reference */
-			if (*arc_flags & ARC_PREFETCH) {
+			if (*arc_flags & ARC_FLAG_PREFETCH) {
 				(void) remove_reference(hdr, hash_lock,
 				    private);
-				hdr->b_flags |= ARC_PREFETCH;
+				hdr->b_flags |= ARC_FLAG_PREFETCH;
 			}
-			if (*arc_flags & ARC_L2CACHE)
-				hdr->b_flags |= ARC_L2CACHE;
-			if (*arc_flags & ARC_L2COMPRESS)
-				hdr->b_flags |= ARC_L2COMPRESS;
+			if (*arc_flags & ARC_FLAG_L2CACHE)
+				hdr->b_flags |= ARC_FLAG_L2CACHE;
+			if (*arc_flags & ARC_FLAG_L2COMPRESS)
+				hdr->b_flags |= ARC_FLAG_L2COMPRESS;
 			if (BP_GET_LEVEL(bp) > 0)
-				hdr->b_flags |= ARC_INDIRECT;
+				hdr->b_flags |= ARC_FLAG_INDIRECT;
 		} else {
 			/* this block is in the ghost cache */
 			ASSERT(GHOST_STATE(hdr->b_state));
@@ -3296,14 +3282,14 @@ top:
 			ASSERT(hdr->b_buf == NULL);
 
 			/* if this is a prefetch, we don't have a reference */
-			if (*arc_flags & ARC_PREFETCH)
-				hdr->b_flags |= ARC_PREFETCH;
+			if (*arc_flags & ARC_FLAG_PREFETCH)
+				hdr->b_flags |= ARC_FLAG_PREFETCH;
 			else
 				add_reference(hdr, hash_lock, private);
-			if (*arc_flags & ARC_L2CACHE)
-				hdr->b_flags |= ARC_L2CACHE;
-			if (*arc_flags & ARC_L2COMPRESS)
-				hdr->b_flags |= ARC_L2COMPRESS;
+			if (*arc_flags & ARC_FLAG_L2CACHE)
+				hdr->b_flags |= ARC_FLAG_L2CACHE;
+			if (*arc_flags & ARC_FLAG_L2COMPRESS)
+				hdr->b_flags |= ARC_FLAG_L2COMPRESS;
 			buf = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
 			buf->b_hdr = hdr;
 			buf->b_data = NULL;
@@ -3325,7 +3311,7 @@ top:
 
 		ASSERT(hdr->b_acb == NULL);
 		hdr->b_acb = acb;
-		hdr->b_flags |= ARC_IO_IN_PROGRESS;
+		hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS;
 
 		if (hdr->b_l2hdr != NULL &&
 		    (vd = hdr->b_l2hdr->b_dev->l2ad_vdev) != NULL) {
@@ -3352,7 +3338,7 @@ top:
 		DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
 		    uint64_t, size, zbookmark_phys_t *, zb);
 		ARCSTAT_BUMP(arcstat_misses);
-		ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
+		ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_FLAG_PREFETCH),
 		    demand, prefetch, hdr->b_type != ARC_BUFC_METADATA,
 		    data, metadata, misses);
 
@@ -3415,12 +3401,12 @@ top:
 				    zio_t *, rzio);
 				ARCSTAT_INCR(arcstat_l2_read_bytes, b_asize);
 
-				if (*arc_flags & ARC_NOWAIT) {
+				if (*arc_flags & ARC_FLAG_NOWAIT) {
 					zio_nowait(rzio);
 					goto out;
 				}
 
-				ASSERT(*arc_flags & ARC_WAIT);
+				ASSERT(*arc_flags & ARC_FLAG_WAIT);
 				if (zio_wait(rzio) == 0)
 					goto out;
 
@@ -3446,12 +3432,12 @@ top:
 		rzio = zio_read(pio, spa, bp, buf->b_data, size,
 		    arc_read_done, buf, priority, zio_flags, zb);
 
-		if (*arc_flags & ARC_WAIT) {
+		if (*arc_flags & ARC_FLAG_WAIT) {
 			rc = zio_wait(rzio);
 			goto out;
 		}
 
-		ASSERT(*arc_flags & ARC_NOWAIT);
+		ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
 		zio_nowait(rzio);
 	}
 
@@ -3522,7 +3508,7 @@ arc_freed(spa_t *spa, const blkptr_t *bp)
 	if (HDR_BUF_AVAILABLE(hdr)) {
 		arc_buf_t *buf = hdr->b_buf;
 		add_reference(hdr, hash_lock, FTAG);
-		hdr->b_flags &= ~ARC_BUF_AVAILABLE;
+		hdr->b_flags &= ~ARC_FLAG_BUF_AVAILABLE;
 		mutex_exit(hash_lock);
 
 		arc_release(buf, FTAG);
@@ -3589,7 +3575,7 @@ arc_clear_callback(arc_buf_t *buf)
 		arc_buf_destroy(buf, FALSE, TRUE);
 	} else {
 		ASSERT(buf == hdr->b_buf);
-		hdr->b_flags |= ARC_BUF_AVAILABLE;
+		hdr->b_flags |= ARC_FLAG_BUF_AVAILABLE;
 		mutex_exit(&buf->b_evict_lock);
 	}
 
@@ -3700,7 +3686,7 @@ arc_release(arc_buf_t *buf, void *tag)
 		nhdr->b_mfu_hits = 0;
 		nhdr->b_mfu_ghost_hits = 0;
 		nhdr->b_l2_hits = 0;
-		nhdr->b_flags = flags & ARC_L2_WRITING;
+		nhdr->b_flags = flags & ARC_FLAG_L2_WRITING;
 		nhdr->b_l2hdr = NULL;
 		nhdr->b_datacnt = 1;
 		nhdr->b_freeze_cksum = NULL;
@@ -3790,7 +3776,7 @@ arc_write_ready(zio_t *zio)
 		mutex_exit(&hdr->b_freeze_lock);
 	}
 	arc_cksum_compute(buf, B_FALSE);
-	hdr->b_flags |= ARC_IO_IN_PROGRESS;
+	hdr->b_flags |= ARC_FLAG_IO_IN_PROGRESS;
 }
 
 /*
@@ -3871,13 +3857,13 @@ arc_write_done(zio_t *zio)
 				ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
 			}
 		}
-		hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
+		hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS;
 		/* if it's not anon, we are doing a scrub */
 		if (!exists && hdr->b_state == arc_anon)
 			arc_access(hdr, hash_lock);
 		mutex_exit(hash_lock);
 	} else {
-		hdr->b_flags &= ~ARC_IO_IN_PROGRESS;
+		hdr->b_flags &= ~ARC_FLAG_IO_IN_PROGRESS;
 	}
 
 	ASSERT(!refcount_is_zero(&hdr->b_refcnt));
@@ -3900,12 +3886,12 @@ arc_write(zio_t *pio, spa_t *spa, uint64_t txg,
 	ASSERT(ready != NULL);
 	ASSERT(done != NULL);
 	ASSERT(!HDR_IO_ERROR(hdr));
-	ASSERT((hdr->b_flags & ARC_IO_IN_PROGRESS) == 0);
+	ASSERT((hdr->b_flags & ARC_FLAG_IO_IN_PROGRESS) == 0);
 	ASSERT(hdr->b_acb == NULL);
 	if (l2arc)
-		hdr->b_flags |= ARC_L2CACHE;
+		hdr->b_flags |= ARC_FLAG_L2CACHE;
 	if (l2arc_compress)
-		hdr->b_flags |= ARC_L2COMPRESS;
+		hdr->b_flags |= ARC_FLAG_L2COMPRESS;
 	callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
 	callback->awcb_ready = ready;
 	callback->awcb_physdone = physdone;
@@ -4395,7 +4381,7 @@ arc_fini(void)
  */
 
 static boolean_t
-l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab)
+l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr)
 {
 	/*
 	 * A buffer is *not* eligible for the L2ARC if it:
@@ -4404,8 +4390,8 @@ l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *ab)
 	 * 3. has an I/O in progress (it may be an incomplete read).
 	 * 4. is flagged not eligible (zfs property).
 	 */
-	if (ab->b_spa != spa_guid || ab->b_l2hdr != NULL ||
-	    HDR_IO_IN_PROGRESS(ab) || !HDR_L2CACHE(ab))
+	if (hdr->b_spa != spa_guid || hdr->b_l2hdr != NULL ||
+	    HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr))
 		return (B_FALSE);
 
 	return (B_TRUE);
@@ -4566,7 +4552,7 @@ l2arc_write_done(zio_t *zio)
 	l2arc_write_callback_t *cb;
 	l2arc_dev_t *dev;
 	list_t *buflist;
-	arc_buf_hdr_t *head, *ab, *ab_prev;
+	arc_buf_hdr_t *head, *hdr, *hdr_prev;
 	l2arc_buf_hdr_t *abl2;
 	kmutex_t *hash_lock;
 	int64_t bytes_dropped = 0;
@@ -4590,17 +4576,17 @@ l2arc_write_done(zio_t *zio)
 	/*
 	 * All writes completed, or an error was hit.
 	 */
-	for (ab = list_prev(buflist, head); ab; ab = ab_prev) {
-		ab_prev = list_prev(buflist, ab);
-		abl2 = ab->b_l2hdr;
+	for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) {
+		hdr_prev = list_prev(buflist, hdr);
+		abl2 = hdr->b_l2hdr;
 
 		/*
 		 * Release the temporary compressed buffer as soon as possible.
 		 */
 		if (abl2->b_compress != ZIO_COMPRESS_OFF)
-			l2arc_release_cdata_buf(ab);
+			l2arc_release_cdata_buf(hdr);
 
-		hash_lock = HDR_LOCK(ab);
+		hash_lock = HDR_LOCK(hdr);
 		if (!mutex_tryenter(hash_lock)) {
 			/*
 			 * This buffer misses out.  It may be in a stage
@@ -4615,19 +4601,19 @@ l2arc_write_done(zio_t *zio)
 			/*
 			 * Error - drop L2ARC entry.
 			 */
-			list_remove(buflist, ab);
+			list_remove(buflist, hdr);
 			ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize);
 			bytes_dropped += abl2->b_asize;
-			ab->b_l2hdr = NULL;
+			hdr->b_l2hdr = NULL;
 			kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
 			arc_space_return(L2HDR_SIZE, ARC_SPACE_L2HDRS);
-			ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
+			ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
 		}
 
 		/*
 		 * Allow ARC to begin reads to this L2ARC entry.
 		 */
-		ab->b_flags &= ~ARC_L2_WRITING;
+		hdr->b_flags &= ~ARC_FLAG_L2_WRITING;
 
 		mutex_exit(hash_lock);
 	}
@@ -4774,7 +4760,7 @@ l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
 {
 	list_t *buflist;
 	l2arc_buf_hdr_t *abl2;
-	arc_buf_hdr_t *ab, *ab_prev;
+	arc_buf_hdr_t *hdr, *hdr_prev;
 	kmutex_t *hash_lock;
 	uint64_t taddr;
 	int64_t bytes_evicted = 0;
@@ -4806,10 +4792,10 @@ l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
 
 top:
 	mutex_enter(&l2arc_buflist_mtx);
-	for (ab = list_tail(buflist); ab; ab = ab_prev) {
-		ab_prev = list_prev(buflist, ab);
+	for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) {
+		hdr_prev = list_prev(buflist, hdr);
 
-		hash_lock = HDR_LOCK(ab);
+		hash_lock = HDR_LOCK(hdr);
 		if (!mutex_tryenter(hash_lock)) {
 			/*
 			 * Missed the hash lock.  Retry.
@@ -4821,19 +4807,19 @@ top:
 			goto top;
 		}
 
-		if (HDR_L2_WRITE_HEAD(ab)) {
+		if (HDR_L2_WRITE_HEAD(hdr)) {
 			/*
 			 * We hit a write head node.  Leave it for
 			 * l2arc_write_done().
 			 */
-			list_remove(buflist, ab);
+			list_remove(buflist, hdr);
 			mutex_exit(hash_lock);
 			continue;
 		}
 
-		if (!all && ab->b_l2hdr != NULL &&
-		    (ab->b_l2hdr->b_daddr > taddr ||
-		    ab->b_l2hdr->b_daddr < dev->l2ad_hand)) {
+		if (!all && hdr->b_l2hdr != NULL &&
+		    (hdr->b_l2hdr->b_daddr > taddr ||
+		    hdr->b_l2hdr->b_daddr < dev->l2ad_hand)) {
 			/*
 			 * We've evicted to the target address,
 			 * or the end of the device.
@@ -4842,7 +4828,7 @@ top:
 			break;
 		}
 
-		if (HDR_FREE_IN_PROGRESS(ab)) {
+		if (HDR_FREE_IN_PROGRESS(hdr)) {
 			/*
 			 * Already on the path to destruction.
 			 */
@@ -4850,45 +4836,45 @@ top:
 			continue;
 		}
 
-		if (ab->b_state == arc_l2c_only) {
-			ASSERT(!HDR_L2_READING(ab));
+		if (hdr->b_state == arc_l2c_only) {
+			ASSERT(!HDR_L2_READING(hdr));
 			/*
 			 * This doesn't exist in the ARC.  Destroy.
 			 * arc_hdr_destroy() will call list_remove()
 			 * and decrement arcstat_l2_size.
 			 */
-			arc_change_state(arc_anon, ab, hash_lock);
-			arc_hdr_destroy(ab);
+			arc_change_state(arc_anon, hdr, hash_lock);
+			arc_hdr_destroy(hdr);
 		} else {
 			/*
 			 * Invalidate issued or about to be issued
 			 * reads, since we may be about to write
 			 * over this location.
 			 */
-			if (HDR_L2_READING(ab)) {
+			if (HDR_L2_READING(hdr)) {
 				ARCSTAT_BUMP(arcstat_l2_evict_reading);
-				ab->b_flags |= ARC_L2_EVICTED;
+				hdr->b_flags |= ARC_FLAG_L2_EVICTED;
 			}
 
 			/*
 			 * Tell ARC this no longer exists in L2ARC.
 			 */
-			if (ab->b_l2hdr != NULL) {
-				abl2 = ab->b_l2hdr;
+			if (hdr->b_l2hdr != NULL) {
+				abl2 = hdr->b_l2hdr;
 				ARCSTAT_INCR(arcstat_l2_asize, -abl2->b_asize);
 				bytes_evicted += abl2->b_asize;
-				ab->b_l2hdr = NULL;
+				hdr->b_l2hdr = NULL;
 				kmem_free(abl2, sizeof (l2arc_buf_hdr_t));
 				arc_space_return(L2HDR_SIZE, ARC_SPACE_L2HDRS);
-				ARCSTAT_INCR(arcstat_l2_size, -ab->b_size);
+				ARCSTAT_INCR(arcstat_l2_size, -hdr->b_size);
 			}
-			list_remove(buflist, ab);
+			list_remove(buflist, hdr);
 
 			/*
 			 * This may have been leftover after a
 			 * failed write.
 			 */
-			ab->b_flags &= ~ARC_L2_WRITING;
+			hdr->b_flags &= ~ARC_FLAG_L2_WRITING;
 		}
 		mutex_exit(hash_lock);
 	}
@@ -4901,7 +4887,7 @@ top:
 /*
  * Find and write ARC buffers to the L2ARC device.
  *
- * An ARC_L2_WRITING flag is set so that the L2ARC buffers are not valid
+ * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid
  * for reading until they have completed writing.
  * The headroom_boost is an in-out parameter used to maintain headroom boost
  * state between calls to this function.
@@ -4913,7 +4899,7 @@ static uint64_t
 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
     boolean_t *headroom_boost)
 {
-	arc_buf_hdr_t *ab, *ab_prev, *head;
+	arc_buf_hdr_t *hdr, *hdr_prev, *head;
 	list_t *list;
 	uint64_t write_asize, write_psize, write_sz, headroom,
 	    buf_compress_minsz;
@@ -4935,7 +4921,7 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
 	write_sz = write_asize = write_psize = 0;
 	full = B_FALSE;
 	head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
-	head->b_flags |= ARC_L2_WRITE_HEAD;
+	head->b_flags |= ARC_FLAG_L2_WRITE_HEAD;
 
 	/*
 	 * We will want to try to compress buffers that are at least 2x the
@@ -4959,25 +4945,25 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
 		 * head of the ARC lists rather than the tail.
 		 */
 		if (arc_warm == B_FALSE)
-			ab = list_head(list);
+			hdr = list_head(list);
 		else
-			ab = list_tail(list);
+			hdr = list_tail(list);
 
 		headroom = target_sz * l2arc_headroom;
 		if (do_headroom_boost)
 			headroom = (headroom * l2arc_headroom_boost) / 100;
 
-		for (; ab; ab = ab_prev) {
+		for (; hdr; hdr = hdr_prev) {
 			l2arc_buf_hdr_t *l2hdr;
 			kmutex_t *hash_lock;
 			uint64_t buf_sz;
 
 			if (arc_warm == B_FALSE)
-				ab_prev = list_next(list, ab);
+				hdr_prev = list_next(list, hdr);
 			else
-				ab_prev = list_prev(list, ab);
+				hdr_prev = list_prev(list, hdr);
 
-			hash_lock = HDR_LOCK(ab);
+			hash_lock = HDR_LOCK(hdr);
 			if (!mutex_tryenter(hash_lock)) {
 				/*
 				 * Skip this buffer rather than waiting.
@@ -4985,7 +4971,7 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
 				continue;
 			}
 
-			passed_sz += ab->b_size;
+			passed_sz += hdr->b_size;
 			if (passed_sz > headroom) {
 				/*
 				 * Searched too far.
@@ -4994,12 +4980,12 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
 				break;
 			}
 
-			if (!l2arc_write_eligible(guid, ab)) {
+			if (!l2arc_write_eligible(guid, hdr)) {
 				mutex_exit(hash_lock);
 				continue;
 			}
 
-			if ((write_sz + ab->b_size) > target_sz) {
+			if ((write_sz + hdr->b_size) > target_sz) {
 				full = B_TRUE;
 				mutex_exit(hash_lock);
 				break;
@@ -5029,32 +5015,32 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
 			l2hdr->b_dev = dev;
 			arc_space_consume(L2HDR_SIZE, ARC_SPACE_L2HDRS);
 
-			ab->b_flags |= ARC_L2_WRITING;
+			hdr->b_flags |= ARC_FLAG_L2_WRITING;
 
 			/*
 			 * Temporarily stash the data buffer in b_tmp_cdata.
 			 * The subsequent write step will pick it up from
-			 * there. This is because can't access ab->b_buf
+			 * there. This is because can't access hdr->b_buf
 			 * without holding the hash_lock, which we in turn
 			 * can't access without holding the ARC list locks
 			 * (which we want to avoid during compression/writing)
 			 */
 			l2hdr->b_compress = ZIO_COMPRESS_OFF;
-			l2hdr->b_asize = ab->b_size;
-			l2hdr->b_tmp_cdata = ab->b_buf->b_data;
+			l2hdr->b_asize = hdr->b_size;
+			l2hdr->b_tmp_cdata = hdr->b_buf->b_data;
 			l2hdr->b_hits = 0;
 
-			buf_sz = ab->b_size;
-			ab->b_l2hdr = l2hdr;
+			buf_sz = hdr->b_size;
+			hdr->b_l2hdr = l2hdr;
 
-			list_insert_head(dev->l2ad_buflist, ab);
+			list_insert_head(dev->l2ad_buflist, hdr);
 
 			/*
 			 * Compute and store the buffer cksum before
 			 * writing.  On debug the cksum is verified first.
 			 */
-			arc_cksum_verify(ab->b_buf);
-			arc_cksum_compute(ab->b_buf, B_TRUE);
+			arc_cksum_verify(hdr->b_buf);
+			arc_cksum_compute(hdr->b_buf, B_TRUE);
 
 			mutex_exit(hash_lock);
 
@@ -5080,21 +5066,22 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
 	 * and work backwards, retracing the course of the buffer selector
 	 * loop above.
 	 */
-	for (ab = list_prev(dev->l2ad_buflist, head); ab;
-	    ab = list_prev(dev->l2ad_buflist, ab)) {
+	for (hdr = list_prev(dev->l2ad_buflist, head); hdr;
+	    hdr = list_prev(dev->l2ad_buflist, hdr)) {
 		l2arc_buf_hdr_t *l2hdr;
 		uint64_t buf_sz;
 
 		/*
 		 * We shouldn't need to lock the buffer here, since we flagged
-		 * it as ARC_L2_WRITING in the previous step, but we must take
-		 * care to only access its L2 cache parameters. In particular,
-		 * ab->b_buf may be invalid by now due to ARC eviction.
+		 * it as ARC_FLAG_L2_WRITING in the previous step, but we must
+		 * take care to only access its L2 cache parameters. In
+		 * particular, hdr->b_buf may be invalid by now due to
+		 * ARC eviction.
 		 */
-		l2hdr = ab->b_l2hdr;
+		l2hdr = hdr->b_l2hdr;
 		l2hdr->b_daddr = dev->l2ad_hand;
 
-		if (!l2arc_nocompress && (ab->b_flags & ARC_L2COMPRESS) &&
+		if (!l2arc_nocompress && (hdr->b_flags & ARC_FLAG_L2COMPRESS) &&
 		    l2hdr->b_asize >= buf_compress_minsz) {
 			if (l2arc_compress_buf(l2hdr)) {
 				/*
@@ -5298,9 +5285,9 @@ l2arc_decompress_zio(zio_t *zio, arc_buf_hdr_t *hdr, enum zio_compress c)
  * done, we can dispose of it.
  */
 static void
-l2arc_release_cdata_buf(arc_buf_hdr_t *ab)
+l2arc_release_cdata_buf(arc_buf_hdr_t *hdr)
 {
-	l2arc_buf_hdr_t *l2hdr = ab->b_l2hdr;
+	l2arc_buf_hdr_t *l2hdr = hdr->b_l2hdr;
 
 	if (l2hdr->b_compress == ZIO_COMPRESS_LZ4) {
 		/*
@@ -5308,7 +5295,7 @@ l2arc_release_cdata_buf(arc_buf_hdr_t *ab)
 		 * temporary buffer for it, so now we need to release it.
 		 */
 		ASSERT(l2hdr->b_tmp_cdata != NULL);
-		zio_data_buf_free(l2hdr->b_tmp_cdata, ab->b_size);
+		zio_data_buf_free(l2hdr->b_tmp_cdata, hdr->b_size);
 	}
 	l2hdr->b_tmp_cdata = NULL;
 }
diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c
index 48e0e347a..4e0f857c5 100644
--- a/module/zfs/dbuf.c
+++ b/module/zfs/dbuf.c
@@ -653,7 +653,7 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t *flags)
 {
 	dnode_t *dn;
 	zbookmark_phys_t zb;
-	uint32_t aflags = ARC_NOWAIT;
+	uint32_t aflags = ARC_FLAG_NOWAIT;
 	int err;
 
 	DB_DNODE_ENTER(db);
@@ -707,9 +707,9 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t *flags)
 	mutex_exit(&db->db_mtx);
 
 	if (DBUF_IS_L2CACHEABLE(db))
-		aflags |= ARC_L2CACHE;
+		aflags |= ARC_FLAG_L2CACHE;
 	if (DBUF_IS_L2COMPRESSIBLE(db))
-		aflags |= ARC_L2COMPRESS;
+		aflags |= ARC_FLAG_L2COMPRESS;
 
 	SET_BOOKMARK(&zb, db->db_objset->os_dsl_dataset ?
 	    db->db_objset->os_dsl_dataset->ds_object : DMU_META_OBJSET,
@@ -721,7 +721,7 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t *flags)
 	    dbuf_read_done, db, ZIO_PRIORITY_SYNC_READ,
 	    (*flags & DB_RF_CANFAIL) ? ZIO_FLAG_CANFAIL : ZIO_FLAG_MUSTSUCCEED,
 	    &aflags, &zb);
-	if (aflags & ARC_CACHED)
+	if (aflags & ARC_FLAG_CACHED)
 		*flags |= DB_RF_CACHED;
 
 	return (SET_ERROR(err));
@@ -2028,7 +2028,8 @@ dbuf_prefetch(dnode_t *dn, uint64_t blkid, zio_priority_t prio)
 	if (dbuf_findbp(dn, 0, blkid, TRUE, &db, &bp, NULL) == 0) {
 		if (bp && !BP_IS_HOLE(bp) && !BP_IS_EMBEDDED(bp)) {
 			dsl_dataset_t *ds = dn->dn_objset->os_dsl_dataset;
-			uint32_t aflags = ARC_NOWAIT | ARC_PREFETCH;
+			arc_flags_t aflags =
+			    ARC_FLAG_NOWAIT | ARC_FLAG_PREFETCH;
 			zbookmark_phys_t zb;
 
 			SET_BOOKMARK(&zb, ds ? ds->ds_object : DMU_META_OBJSET,
diff --git a/module/zfs/dmu_diff.c b/module/zfs/dmu_diff.c
index 32e451a77..91415d0d2 100644
--- a/module/zfs/dmu_diff.c
+++ b/module/zfs/dmu_diff.c
@@ -129,7 +129,7 @@ diff_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
 	} else if (zb->zb_level == 0) {
 		dnode_phys_t *blk;
 		arc_buf_t *abuf;
-		uint32_t aflags = ARC_WAIT;
+		arc_flags_t aflags = ARC_FLAG_WAIT;
 		int blksz = BP_GET_LSIZE(bp);
 		int i;
 
diff --git a/module/zfs/dmu_objset.c b/module/zfs/dmu_objset.c
index 6ef6adbd9..bc1aa1286 100644
--- a/module/zfs/dmu_objset.c
+++ b/module/zfs/dmu_objset.c
@@ -306,15 +306,15 @@ dmu_objset_open_impl(spa_t *spa, dsl_dataset_t *ds, blkptr_t *bp,
 	os->os_spa = spa;
 	os->os_rootbp = bp;
 	if (!BP_IS_HOLE(os->os_rootbp)) {
-		uint32_t aflags = ARC_WAIT;
+		arc_flags_t aflags = ARC_FLAG_WAIT;
 		zbookmark_phys_t zb;
 		SET_BOOKMARK(&zb, ds ? ds->ds_object : DMU_META_OBJSET,
 		    ZB_ROOT_OBJECT, ZB_ROOT_LEVEL, ZB_ROOT_BLKID);
 
 		if (DMU_OS_IS_L2CACHEABLE(os))
-			aflags |= ARC_L2CACHE;
+			aflags |= ARC_FLAG_L2CACHE;
 		if (DMU_OS_IS_L2COMPRESSIBLE(os))
-			aflags |= ARC_L2COMPRESS;
+			aflags |= ARC_FLAG_L2COMPRESS;
 
 		dprintf_bp(os->os_rootbp, "reading %s", "");
 		err = arc_read(NULL, spa, os->os_rootbp,
diff --git a/module/zfs/dmu_send.c b/module/zfs/dmu_send.c
index dddc8094f..8fa6797c4 100644
--- a/module/zfs/dmu_send.c
+++ b/module/zfs/dmu_send.c
@@ -486,7 +486,7 @@ backup_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
 		dnode_phys_t *blk;
 		int i;
 		int blksz = BP_GET_LSIZE(bp);
-		uint32_t aflags = ARC_WAIT;
+		arc_flags_t aflags = ARC_FLAG_WAIT;
 		arc_buf_t *abuf;
 
 		if (arc_read(NULL, spa, bp, arc_getbuf_func, &abuf,
@@ -504,7 +504,7 @@ backup_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
 		}
 		(void) arc_buf_remove_ref(abuf, &abuf);
 	} else if (type == DMU_OT_SA) {
-		uint32_t aflags = ARC_WAIT;
+		arc_flags_t aflags = ARC_FLAG_WAIT;
 		arc_buf_t *abuf;
 		int blksz = BP_GET_LSIZE(bp);
 
@@ -521,8 +521,8 @@ backup_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
 		err = dump_write_embedded(dsp, zb->zb_object,
 		    zb->zb_blkid * blksz, blksz, bp);
 	} else { /* it's a level-0 block of a regular object */
-		uint32_t aflags = ARC_WAIT;
 		uint64_t offset;
+		arc_flags_t aflags = ARC_FLAG_WAIT;
 		arc_buf_t *abuf;
 		int blksz = BP_GET_LSIZE(bp);
 
diff --git a/module/zfs/dmu_traverse.c b/module/zfs/dmu_traverse.c
index 8673132a0..6c69a2339 100644
--- a/module/zfs/dmu_traverse.c
+++ b/module/zfs/dmu_traverse.c
@@ -177,7 +177,7 @@ static void
 traverse_prefetch_metadata(traverse_data_t *td,
     const blkptr_t *bp, const zbookmark_phys_t *zb)
 {
-	uint32_t flags = ARC_NOWAIT | ARC_PREFETCH;
+	arc_flags_t flags = ARC_FLAG_NOWAIT | ARC_FLAG_PREFETCH;
 
 	if (!(td->td_flags & TRAVERSE_PREFETCH_METADATA))
 		return;
@@ -273,7 +273,7 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
 	}
 
 	if (BP_GET_LEVEL(bp) > 0) {
-		uint32_t flags = ARC_WAIT;
+		uint32_t flags = ARC_FLAG_WAIT;
 		int32_t i;
 		int32_t epb = BP_GET_LSIZE(bp) >> SPA_BLKPTRSHIFT;
 		zbookmark_phys_t *czb;
@@ -307,7 +307,7 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
 		kmem_free(czb, sizeof (zbookmark_phys_t));
 
 	} else if (BP_GET_TYPE(bp) == DMU_OT_DNODE) {
-		uint32_t flags = ARC_WAIT;
+		uint32_t flags = ARC_FLAG_WAIT;
 		int32_t i;
 		int32_t epb = BP_GET_LSIZE(bp) >> DNODE_SHIFT;
 		dnode_phys_t *cdnp;
@@ -331,7 +331,7 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp,
 				break;
 		}
 	} else if (BP_GET_TYPE(bp) == DMU_OT_OBJSET) {
-		uint32_t flags = ARC_WAIT;
+		arc_flags_t flags = ARC_FLAG_WAIT;
 		objset_phys_t *osp;
 		dnode_phys_t *mdnp, *gdnp, *udnp;
 
@@ -448,7 +448,7 @@ traverse_prefetcher(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
     const zbookmark_phys_t *zb, const dnode_phys_t *dnp, void *arg)
 {
 	prefetch_data_t *pfd = arg;
-	uint32_t aflags = ARC_NOWAIT | ARC_PREFETCH;
+	arc_flags_t aflags = ARC_FLAG_NOWAIT | ARC_FLAG_PREFETCH;
 
 	ASSERT(pfd->pd_bytes_fetched >= 0);
 	if (pfd->pd_cancel)
@@ -545,7 +545,7 @@ traverse_impl(spa_t *spa, dsl_dataset_t *ds, uint64_t objset, blkptr_t *rootbp,
 
 	/* See comment on ZIL traversal in dsl_scan_visitds. */
 	if (ds != NULL && !ds->ds_is_snapshot && !BP_IS_HOLE(rootbp)) {
-		uint32_t flags = ARC_WAIT;
+		uint32_t flags = ARC_FLAG_WAIT;
 		objset_phys_t *osp;
 		arc_buf_t *buf;
 
diff --git a/module/zfs/dsl_scan.c b/module/zfs/dsl_scan.c
index 6b9b04a0e..048935971 100644
--- a/module/zfs/dsl_scan.c
+++ b/module/zfs/dsl_scan.c
@@ -590,7 +590,7 @@ dsl_scan_prefetch(dsl_scan_t *scn, arc_buf_t *buf, blkptr_t *bp,
     uint64_t objset, uint64_t object, uint64_t blkid)
 {
 	zbookmark_phys_t czb;
-	uint32_t flags = ARC_NOWAIT | ARC_PREFETCH;
+	arc_flags_t flags = ARC_FLAG_NOWAIT | ARC_FLAG_PREFETCH;
 
 	if (zfs_no_scrub_prefetch)
 		return;
@@ -655,7 +655,7 @@ dsl_scan_recurse(dsl_scan_t *scn, dsl_dataset_t *ds, dmu_objset_type_t ostype,
 	int err;
 
 	if (BP_GET_LEVEL(bp) > 0) {
-		uint32_t flags = ARC_WAIT;
+		arc_flags_t flags = ARC_FLAG_WAIT;
 		int i;
 		blkptr_t *cbp;
 		int epb = BP_GET_LSIZE(bp) >> SPA_BLKPTRSHIFT;
@@ -682,7 +682,7 @@ dsl_scan_recurse(dsl_scan_t *scn, dsl_dataset_t *ds, dmu_objset_type_t ostype,
 		}
 		(void) arc_buf_remove_ref(buf, &buf);
 	} else if (BP_GET_TYPE(bp) == DMU_OT_DNODE) {
-		uint32_t flags = ARC_WAIT;
+		arc_flags_t flags = ARC_FLAG_WAIT;
 		dnode_phys_t *cdnp;
 		int i, j;
 		int epb = BP_GET_LSIZE(bp) >> DNODE_SHIFT;
@@ -708,7 +708,7 @@ dsl_scan_recurse(dsl_scan_t *scn, dsl_dataset_t *ds, dmu_objset_type_t ostype,
 
 		(void) arc_buf_remove_ref(buf, &buf);
 	} else if (BP_GET_TYPE(bp) == DMU_OT_OBJSET) {
-		uint32_t flags = ARC_WAIT;
+		arc_flags_t flags = ARC_FLAG_WAIT;
 		objset_phys_t *osp;
 		arc_buf_t *buf;
 
diff --git a/module/zfs/spa_stats.c b/module/zfs/spa_stats.c
index 3e39dba2c..2b8559b5d 100644
--- a/module/zfs/spa_stats.c
+++ b/module/zfs/spa_stats.c
@@ -200,7 +200,7 @@ spa_read_history_add(spa_t *spa, const zbookmark_phys_t *zb, uint32_t aflags)
 	if (zfs_read_history == 0 && ssh->size == 0)
 		return;
 
-	if (zfs_read_history_hits == 0 && (aflags & ARC_CACHED))
+	if (zfs_read_history_hits == 0 && (aflags & ARC_FLAG_CACHED))
 		return;
 
 	srh = kmem_zalloc(sizeof (spa_read_history_t), KM_SLEEP);
diff --git a/module/zfs/zil.c b/module/zfs/zil.c
index ff4d2cec0..6a3885816 100644
--- a/module/zfs/zil.c
+++ b/module/zfs/zil.c
@@ -204,7 +204,7 @@ zil_read_log_block(zilog_t *zilog, const blkptr_t *bp, blkptr_t *nbp, void *dst,
     char **end)
 {
 	enum zio_flag zio_flags = ZIO_FLAG_CANFAIL;
-	uint32_t aflags = ARC_WAIT;
+	arc_flags_t aflags = ARC_FLAG_WAIT;
 	arc_buf_t *abuf = NULL;
 	zbookmark_phys_t zb;
 	int error;
@@ -280,7 +280,7 @@ zil_read_log_data(zilog_t *zilog, const lr_write_t *lr, void *wbuf)
 {
 	enum zio_flag zio_flags = ZIO_FLAG_CANFAIL;
 	const blkptr_t *bp = &lr->lr_blkptr;
-	uint32_t aflags = ARC_WAIT;
+	arc_flags_t aflags = ARC_FLAG_WAIT;
 	arc_buf_t *abuf = NULL;
 	zbookmark_phys_t zb;
 	int error;
diff --git a/module/zfs/zio.c b/module/zfs/zio.c
index 1e5be8bfc..c378742ed 100644
--- a/module/zfs/zio.c
+++ b/module/zfs/zio.c
@@ -2241,7 +2241,7 @@ zio_ddt_collision(zio_t *zio, ddt_t *ddt, ddt_entry_t *dde)
 
 		if (ddp->ddp_phys_birth != 0) {
 			arc_buf_t *abuf = NULL;
-			uint32_t aflags = ARC_WAIT;
+			arc_flags_t aflags = ARC_FLAG_WAIT;
 			blkptr_t blk = *zio->io_bp;
 			int error;