6.10-stable review patch. If anyone has any objections, please let me know.
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From: Shin'ichiro Kawasaki shinichiro.kawasaki@wdc.com
commit 43aec4d01bd2ce961817a777b3846f8318f398e4 upstream.
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 well 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. It always returns zero and sets NULL to the given 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 Reviewed-by: Damien Le Moal dlemoal@kernel.org Reviewed-by: Chao Yu chao@kernel.org Reviewed-by: Christoph Hellwig hch@lst.de Signed-off-by: Jaegeuk Kim jaegeuk@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/f2fs/segment.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/fs/f2fs/segment.c +++ b/fs/f2fs/segment.c @@ -1290,6 +1290,13 @@ static int __submit_discard_cmd(struct f wait_list, issued); return 0; } + + /* + * Issue discard for conventional zones only if the device + * supports discard. + */ + if (!bdev_max_discard_sectors(bdev)) + return -EOPNOTSUPP; } #endif