f2fs: Fix use of number of devices

For a single device mount using a zoned block device, the zone
information for the device is stored in the sbi->devs single entry
array and sbi->s_ndevs is set to 1. This differs from a single device
mount using a regular block device which does not allocate sbi->devs
and sets sbi->s_ndevs to 0.

However, sbi->s_devs == 0 condition is used throughout the code to
differentiate a single device mount from a multi-device mount where
sbi->s_ndevs is always larger than 1. This results in problems with
single zoned block device volumes as these are treated as multi-device
mounts but do not have the start_blk and end_blk information set. One
of the problem observed is skipping of zone discard issuing resulting in
write commands being issued to full zones or unaligned to a zone write
pointer.

Fix this problem by simply treating the cases sbi->s_ndevs == 0 (single
regular block device mount) and sbi->s_ndevs == 1 (single zoned block
device mount) in the same manner. This is done by introducing the
helper function f2fs_is_multi_device() and using this helper in place
of direct tests of sbi->s_ndevs value, improving code readability.

Fixes: 7bb3a371d199 ("f2fs: Fix zoned block device support")
Cc: <stable@vger.kernel.org>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 11 insertions, 6 deletions

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 9727944139f2..d87dfa5aa112 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -220,12 +220,14 @@ struct block_device *f2fs_target_device(struct f2fs_sb_info *sbi,
 	struct block_device *bdev = sbi->sb->s_bdev;
 	int i;
 
-	for (i = 0; i < sbi->s_ndevs; i++) {
-		if (FDEV(i).start_blk <= blk_addr &&
-					FDEV(i).end_blk >= blk_addr) {
-			blk_addr -= FDEV(i).start_blk;
-			bdev = FDEV(i).bdev;
-			break;
+	if (f2fs_is_multi_device(sbi)) {
+		for (i = 0; i < sbi->s_ndevs; i++) {
+			if (FDEV(i).start_blk <= blk_addr &&
+			    FDEV(i).end_blk >= blk_addr) {
+				blk_addr -= FDEV(i).start_blk;
+				bdev = FDEV(i).bdev;
+				break;
+			}
 		}
 	}
 	if (bio) {
@@ -239,6 +241,9 @@ int f2fs_target_device_index(struct f2fs_sb_info *sbi, block_t blkaddr)
 {
 	int i;
 
+	if (!f2fs_is_multi_device(sbi))
+		return 0;
+
 	for (i = 0; i < sbi->s_ndevs; i++)
 		if (FDEV(i).start_blk <= blkaddr && FDEV(i).end_blk >= blkaddr)
 			return i;