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, 12 insertions, 1 deletions

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 87f75ebd2fd6..7bea1bc6589f 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1366,6 +1366,17 @@ static inline bool time_to_inject(struct f2fs_sb_info *sbi, int type)
 }
 #endif
 
+/*
+ * Test if the mounted volume is a multi-device volume.
+ *   - For a single regular disk volume, sbi->s_ndevs is 0.
+ *   - For a single zoned disk volume, sbi->s_ndevs is 1.
+ *   - For a multi-device volume, sbi->s_ndevs is always 2 or more.
+ */
+static inline bool f2fs_is_multi_device(struct f2fs_sb_info *sbi)
+{
+	return sbi->s_ndevs > 1;
+}
+
 /* For write statistics. Suppose sector size is 512 bytes,
  * and the return value is in kbytes. s is of struct f2fs_sb_info.
  */
@@ -3615,7 +3626,7 @@ static inline bool f2fs_force_buffered_io(struct inode *inode,
 
 	if (f2fs_post_read_required(inode))
 		return true;
-	if (sbi->s_ndevs)
+	if (f2fs_is_multi_device(sbi))
 		return true;
 	/*
 	 * for blkzoned device, fallback direct IO to buffered IO, so