| Message ID | 20240816022353.734136-1-shinichiro.kawasaki@wdc.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [f2fs-dev] f2fs: check discard support for conventional zones | expand |
Thank you for the comments. Will reflect them and post v2.
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c index 78c3198a6308..e10bf3c4eed5 100644 --- a/fs/f2fs/segment.c +++ b/fs/f2fs/segment.c @@ -1281,6 +1281,8 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi, __submit_zone_reset_cmd(sbi, dc, flag, wait_list, issued); return 0; + } else if (!bdev_max_discard_sectors(bdev)) { + return -EOPNOTSUPP; } } #endif
As the helper function f2fs_bdev_support_discard() shows, f2fs checks if the target block devices support discard by calling bdev_max_discard_sectors() and bdev_is_zoned(). This check works good for most cases, but it does not work for conventional zones on zoned block devices. F2fs assumes that zoned block devices support discard, and calls __submit_discard_cmd(). When __submit_discard_cmd() is called for sequential write required zones, it works fine since __submit_discard_cmd() issues zone reset commands instead of discard commands. However, when __submit_discard_cmd() is called for conventional zones, __blkdev_issue_discard() is called even when the devices do not support discard. The inappropriate __blkdev_issue_discard() call was not a problem before the commit 30f1e7241422 ("block: move discard checks into the ioctl handler") because __blkdev_issue_discard() checked if the target devices support discard or not. If not, it returned EOPNOTSUPP. After the commit, __blkdev_issue_discard() no longer checks it and always returns zero and sets NULL to the give bio pointer. This NULL pointer triggers f2fs_bug_on() in __submit_discard_cmd(). The BUG is recreated with the commands below at the umount step, where /dev/nullb0 is a zoned null_blk with 5GB total size, 128MB zone size and 10 conventional zones. $ mkfs.f2fs -f -m /dev/nullb0 $ mount /dev/nullb0 /mnt $ for ((i=0;i<5;i++)); do dd if=/dev/zero of=/mnt/test bs=65536 count=1600 conv=fsync; done $ umount /mnt To fix the BUG, avoid the inappropriate __blkdev_issue_discard() call. When discard is requested for conventional zones, check if the device supports discard or not. If not, return EOPNOTSUPP. Fixes: 30f1e7241422 ("block: move discard checks into the ioctl handler") Cc: stable@vger.kernel.org Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com> --- fs/f2fs/segment.c | 2 ++ 1 file changed, 2 insertions(+)