vdev_disk: ensure trim errors are returned immediately

After 08fd5ccc3, the discard issuing code was organised such that if
requesting an async discard or secure erase failed before the IO was
issued (that is, calling __blkdev_issue_discard() returned an error),
the failed zio would never be executed, resulting in txg_sync hanging
forever waiting for IO to finish.

This commit fixes that by immediately executing a failed zio on error.
To handle the successful synchronous op case, we fake an async op by,
when not using an asynchronous submission method, queuing the successful
result zio as part of the discard handler.

Since it was hard to understand the differences between discard and
secure erase, and sync and async, across different kernel versions, I've
commented and reorganised the code a bit to try and make everything more
contained and linear.

Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Signed-off-by: Rob Norris <[email protected]>
(cherry picked from commit ba9f587a77e6893390c752491dfacb6ee5d52023)

1 files changed, 86 insertions, 45 deletions

diff --git a/module/os/linux/zfs/vdev_disk.c b/module/os/linux/zfs/vdev_disk.c
index 62c7aa14f..12157d3b6 100644
--- a/module/os/linux/zfs/vdev_disk.c
+++ b/module/os/linux/zfs/vdev_disk.c
@@ -1243,8 +1243,6 @@ vdev_disk_io_flush(struct block_device *bdev, zio_t *zio)
 	return (0);
 }
 
-#if defined(HAVE_BLKDEV_ISSUE_SECURE_ERASE) || \
-	defined(HAVE_BLKDEV_ISSUE_DISCARD_ASYNC)
 BIO_END_IO_PROTO(vdev_disk_discard_end_io, bio, error)
 {
 	zio_t *zio = bio->bi_private;
@@ -1259,54 +1257,99 @@ BIO_END_IO_PROTO(vdev_disk_discard_end_io, bio, error)
 	zio_interrupt(zio);
 }
 
+/*
+ * Wrappers for the different secure erase and discard APIs. We use async
+ * when available; in this case, *biop is set to the last bio in the chain.
+ */
 static int
-vdev_issue_discard_trim(zio_t *zio, unsigned long flags)
+vdev_bdev_issue_secure_erase(zfs_bdev_handle_t *bdh, sector_t sector,
+    sector_t nsect, struct bio **biop)
 {
-	int ret;
-	struct bio *bio = NULL;
+	*biop = NULL;
+	int error;
 
-#if defined(BLKDEV_DISCARD_SECURE)
-	ret = - __blkdev_issue_discard(
-	    BDH_BDEV(((vdev_disk_t *)zio->io_vd->vdev_tsd)->vd_bdh),
-	    zio->io_offset >> 9, zio->io_size >> 9, GFP_NOFS, flags, &bio);
+#if defined(HAVE_BLKDEV_ISSUE_SECURE_ERASE)
+	error = blkdev_issue_secure_erase(BDH_BDEV(bdh),
+	    sector, nsect, GFP_NOFS);
+#elif defined(HAVE_BLKDEV_ISSUE_DISCARD_ASYNC_FLAGS)
+	error = __blkdev_issue_discard(BDH_BDEV(bdh),
+	    sector, nsect, GFP_NOFS, BLKDEV_DISCARD_SECURE, biop);
+#elif defined(HAVE_BLKDEV_ISSUE_DISCARD_FLAGS)
+	error = blkdev_issue_discard(BDH_BDEV(bdh),
+	    sector, nsect, GFP_NOFS, BLKDEV_DISCARD_SECURE);
 #else
-	(void) flags;
-	ret = - __blkdev_issue_discard(
-	    BDH_BDEV(((vdev_disk_t *)zio->io_vd->vdev_tsd)->vd_bdh),
-	    zio->io_offset >> 9, zio->io_size >> 9, GFP_NOFS, &bio);
+#error "unsupported kernel"
 #endif
-	if (!ret && bio) {
-		bio->bi_private = zio;
-		bio->bi_end_io = vdev_disk_discard_end_io;
-		vdev_submit_bio(bio);
-	}
-	return (ret);
+
+	return (error);
 }
+
+static int
+vdev_bdev_issue_discard(zfs_bdev_handle_t *bdh, sector_t sector,
+    sector_t nsect, struct bio **biop)
+{
+	*biop = NULL;
+	int error;
+
+#if defined(HAVE_BLKDEV_ISSUE_DISCARD_ASYNC_FLAGS)
+	error = __blkdev_issue_discard(BDH_BDEV(bdh),
+	    sector, nsect, GFP_NOFS, 0, biop);
+#elif defined(HAVE_BLKDEV_ISSUE_DISCARD_ASYNC_NOFLAGS)
+	error = __blkdev_issue_discard(BDH_BDEV(bdh),
+	    sector, nsect, GFP_NOFS, biop);
+#elif defined(HAVE_BLKDEV_ISSUE_DISCARD_FLAGS)
+	error = blkdev_issue_discard(BDH_BDEV(bdh),
+	    sector, nsect, GFP_NOFS, 0);
+#elif defined(HAVE_BLKDEV_ISSUE_DISCARD_NOFLAGS)
+	error = blkdev_issue_discard(BDH_BDEV(bdh),
+	    sector, nsect, GFP_NOFS);
+#else
+#error "unsupported kernel"
 #endif
 
+	return (error);
+}
+
+/*
+ * Entry point for TRIM ops. This calls the right wrapper for secure erase or
+ * discard, and then does the appropriate finishing work for error vs success
+ * and async vs sync.
+ */
 static int
 vdev_disk_io_trim(zio_t *zio)
 {
-	unsigned long trim_flags = 0;
-	if (zio->io_trim_flags & ZIO_TRIM_SECURE) {
-#if defined(HAVE_BLKDEV_ISSUE_SECURE_ERASE)
-		return (-blkdev_issue_secure_erase(
-		    BDH_BDEV(((vdev_disk_t *)zio->io_vd->vdev_tsd)->vd_bdh),
-		    zio->io_offset >> 9, zio->io_size >> 9, GFP_NOFS));
-#elif defined(BLKDEV_DISCARD_SECURE)
-		trim_flags |= BLKDEV_DISCARD_SECURE;
-#endif
+	int error;
+	struct bio *bio;
+
+	zfs_bdev_handle_t *bdh = ((vdev_disk_t *)zio->io_vd->vdev_tsd)->vd_bdh;
+	sector_t sector = zio->io_offset >> 9;
+	sector_t nsects = zio->io_size >> 9;
+
+	if (zio->io_trim_flags & ZIO_TRIM_SECURE)
+		error = vdev_bdev_issue_secure_erase(bdh, sector, nsects, &bio);
+	else
+		error = vdev_bdev_issue_discard(bdh, sector, nsects, &bio);
+
+	if (error != 0)
+		return (SET_ERROR(-error));
+
+	if (bio == NULL) {
+		/*
+		 * This was a synchronous op that completed successfully, so
+		 * return it to ZFS immediately.
+		 */
+		zio_interrupt(zio);
+	} else {
+		/*
+		 * This was an asynchronous op; set up completion callback and
+		 * issue it.
+		 */
+		bio->bi_private = zio;
+		bio->bi_end_io = vdev_disk_discard_end_io;
+		vdev_submit_bio(bio);
 	}
-#if defined(HAVE_BLKDEV_ISSUE_SECURE_ERASE) || \
-	defined(HAVE_BLKDEV_ISSUE_DISCARD_ASYNC)
-	return (vdev_issue_discard_trim(zio, trim_flags));
-#elif defined(HAVE_BLKDEV_ISSUE_DISCARD)
-	return (-blkdev_issue_discard(
-	    BDH_BDEV(((vdev_disk_t *)zio->io_vd->vdev_tsd)->vd_bdh),
-	    zio->io_offset >> 9, zio->io_size >> 9, GFP_NOFS, trim_flags));
-#else
-#error "Unsupported kernel"
-#endif
+
+	return (0);
 }
 
 int (*vdev_disk_io_rw_fn)(zio_t *zio) = NULL;
@@ -1381,14 +1424,12 @@ vdev_disk_io_start(zio_t *zio)
 		return;
 
 	case ZIO_TYPE_TRIM:
-		zio->io_error = vdev_disk_io_trim(zio);
+		error = vdev_disk_io_trim(zio);
 		rw_exit(&vd->vd_lock);
-#if defined(HAVE_BLKDEV_ISSUE_SECURE_ERASE)
-		if (zio->io_trim_flags & ZIO_TRIM_SECURE)
-			zio_interrupt(zio);
-#elif defined(HAVE_BLKDEV_ISSUE_DISCARD)
-		zio_interrupt(zio);
-#endif
+		if (error) {
+			zio->io_error = error;
+			zio_execute(zio);
+		}
 		return;
 
 	case ZIO_TYPE_READ: