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-rw-r--r--module/zfs/rrwlock.c88
-rw-r--r--module/zfs/zfs_ioctl.c6
-rw-r--r--module/zfs/zfs_vfsops.c14
3 files changed, 98 insertions, 10 deletions
diff --git a/module/zfs/rrwlock.c b/module/zfs/rrwlock.c
index 29a22534e..51394c01c 100644
--- a/module/zfs/rrwlock.c
+++ b/module/zfs/rrwlock.c
@@ -305,3 +305,91 @@ rrw_tsd_destroy(void *arg)
(void *)curthread, (void *)rn->rn_rrl);
}
}
+
+/*
+ * A reader-mostly lock implementation, tuning above reader-writer locks
+ * for hightly parallel read acquisitions, while pessimizing writes.
+ *
+ * The idea is to split single busy lock into array of locks, so that
+ * each reader can lock only one of them for read, depending on result
+ * of simple hash function. That proportionally reduces lock congestion.
+ * Writer same time has to sequentially aquire write on all the locks.
+ * That makes write aquisition proportionally slower, but in places where
+ * it is used (filesystem unmount) performance is not critical.
+ *
+ * All the functions below are direct wrappers around functions above.
+ */
+void
+rrm_init(rrmlock_t *rrl, boolean_t track_all)
+{
+ int i;
+
+ for (i = 0; i < RRM_NUM_LOCKS; i++)
+ rrw_init(&rrl->locks[i], track_all);
+}
+
+void
+rrm_destroy(rrmlock_t *rrl)
+{
+ int i;
+
+ for (i = 0; i < RRM_NUM_LOCKS; i++)
+ rrw_destroy(&rrl->locks[i]);
+}
+
+void
+rrm_enter(rrmlock_t *rrl, krw_t rw, void *tag)
+{
+ if (rw == RW_READER)
+ rrm_enter_read(rrl, tag);
+ else
+ rrm_enter_write(rrl);
+}
+
+/*
+ * This maps the current thread to a specific lock. Note that the lock
+ * must be released by the same thread that acquired it. We do this
+ * mapping by taking the thread pointer mod a prime number. We examine
+ * only the low 32 bits of the thread pointer, because 32-bit division
+ * is faster than 64-bit division, and the high 32 bits have little
+ * entropy anyway.
+ */
+#define RRM_TD_LOCK() (((uint32_t)(uintptr_t)(curthread)) % RRM_NUM_LOCKS)
+
+void
+rrm_enter_read(rrmlock_t *rrl, void *tag)
+{
+ rrw_enter_read(&rrl->locks[RRM_TD_LOCK()], tag);
+}
+
+void
+rrm_enter_write(rrmlock_t *rrl)
+{
+ int i;
+
+ for (i = 0; i < RRM_NUM_LOCKS; i++)
+ rrw_enter_write(&rrl->locks[i]);
+}
+
+void
+rrm_exit(rrmlock_t *rrl, void *tag)
+{
+ int i;
+
+ if (rrl->locks[0].rr_writer == curthread) {
+ for (i = 0; i < RRM_NUM_LOCKS; i++)
+ rrw_exit(&rrl->locks[i], tag);
+ } else {
+ rrw_exit(&rrl->locks[RRM_TD_LOCK()], tag);
+ }
+}
+
+boolean_t
+rrm_held(rrmlock_t *rrl, krw_t rw)
+{
+ if (rw == RW_WRITER) {
+ return (rrw_held(&rrl->locks[0], rw));
+ } else {
+ return (rrw_held(&rrl->locks[RRM_TD_LOCK()], rw));
+ }
+}
diff --git a/module/zfs/zfs_ioctl.c b/module/zfs/zfs_ioctl.c
index c44927036..d997616ae 100644
--- a/module/zfs/zfs_ioctl.c
+++ b/module/zfs/zfs_ioctl.c
@@ -1451,7 +1451,7 @@ zfs_sb_hold(const char *name, void *tag, zfs_sb_t **zsbp, boolean_t writer)
if (get_zfs_sb(name, zsbp) != 0)
error = zfs_sb_create(name, zsbp);
if (error == 0) {
- rrw_enter(&(*zsbp)->z_teardown_lock, (writer) ? RW_WRITER :
+ rrm_enter(&(*zsbp)->z_teardown_lock, (writer) ? RW_WRITER :
RW_READER, tag);
if ((*zsbp)->z_unmounted) {
/*
@@ -1459,7 +1459,7 @@ zfs_sb_hold(const char *name, void *tag, zfs_sb_t **zsbp, boolean_t writer)
* thread should be just about to disassociate the
* objset from the zsb.
*/
- rrw_exit(&(*zsbp)->z_teardown_lock, tag);
+ rrm_exit(&(*zsbp)->z_teardown_lock, tag);
return (SET_ERROR(EBUSY));
}
}
@@ -1469,7 +1469,7 @@ zfs_sb_hold(const char *name, void *tag, zfs_sb_t **zsbp, boolean_t writer)
static void
zfs_sb_rele(zfs_sb_t *zsb, void *tag)
{
- rrw_exit(&zsb->z_teardown_lock, tag);
+ rrm_exit(&zsb->z_teardown_lock, tag);
if (zsb->z_sb) {
deactivate_super(zsb->z_sb);
diff --git a/module/zfs/zfs_vfsops.c b/module/zfs/zfs_vfsops.c
index ae1bc324b..a7005a2a1 100644
--- a/module/zfs/zfs_vfsops.c
+++ b/module/zfs/zfs_vfsops.c
@@ -771,7 +771,7 @@ zfs_sb_create(const char *osname, zfs_sb_t **zsbp)
mutex_init(&zsb->z_lock, NULL, MUTEX_DEFAULT, NULL);
list_create(&zsb->z_all_znodes, sizeof (znode_t),
offsetof(znode_t, z_link_node));
- rrw_init(&zsb->z_teardown_lock, B_FALSE);
+ rrm_init(&zsb->z_teardown_lock, B_FALSE);
rw_init(&zsb->z_teardown_inactive_lock, NULL, RW_DEFAULT, NULL);
rw_init(&zsb->z_fuid_lock, NULL, RW_DEFAULT, NULL);
@@ -890,7 +890,7 @@ zfs_sb_free(zfs_sb_t *zsb)
mutex_destroy(&zsb->z_znodes_lock);
mutex_destroy(&zsb->z_lock);
list_destroy(&zsb->z_all_znodes);
- rrw_destroy(&zsb->z_teardown_lock);
+ rrm_destroy(&zsb->z_teardown_lock);
rw_destroy(&zsb->z_teardown_inactive_lock);
rw_destroy(&zsb->z_fuid_lock);
for (i = 0; i != ZFS_OBJ_MTX_SZ; i++)
@@ -1221,7 +1221,7 @@ zfs_sb_teardown(zfs_sb_t *zsb, boolean_t unmounting)
}
}
- rrw_enter(&zsb->z_teardown_lock, RW_WRITER, FTAG);
+ rrm_enter(&zsb->z_teardown_lock, RW_WRITER, FTAG);
if (!unmounting) {
/*
@@ -1252,7 +1252,7 @@ zfs_sb_teardown(zfs_sb_t *zsb, boolean_t unmounting)
*/
if (!unmounting && (zsb->z_unmounted || zsb->z_os == NULL)) {
rw_exit(&zsb->z_teardown_inactive_lock);
- rrw_exit(&zsb->z_teardown_lock, FTAG);
+ rrm_exit(&zsb->z_teardown_lock, FTAG);
return (SET_ERROR(EIO));
}
@@ -1280,7 +1280,7 @@ zfs_sb_teardown(zfs_sb_t *zsb, boolean_t unmounting)
*/
if (unmounting) {
zsb->z_unmounted = B_TRUE;
- rrw_exit(&zsb->z_teardown_lock, FTAG);
+ rrm_exit(&zsb->z_teardown_lock, FTAG);
rw_exit(&zsb->z_teardown_inactive_lock);
}
@@ -1599,7 +1599,7 @@ zfs_resume_fs(zfs_sb_t *zsb, const char *osname)
znode_t *zp;
uint64_t sa_obj = 0;
- ASSERT(RRW_WRITE_HELD(&zsb->z_teardown_lock));
+ ASSERT(RRM_WRITE_HELD(&zsb->z_teardown_lock));
ASSERT(RW_WRITE_HELD(&zsb->z_teardown_inactive_lock));
/*
@@ -1663,7 +1663,7 @@ zfs_resume_fs(zfs_sb_t *zsb, const char *osname)
bail:
/* release the VFS ops */
rw_exit(&zsb->z_teardown_inactive_lock);
- rrw_exit(&zsb->z_teardown_lock, FTAG);
+ rrm_exit(&zsb->z_teardown_lock, FTAG);
if (err) {
/*
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-15 12:32:20 +0000