The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x bc8aeb04fd80cb8cfae3058445c84410fd0beb5e # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024120612-helmet-unwed-8cfe@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From bc8aeb04fd80cb8cfae3058445c84410fd0beb5e Mon Sep 17 00:00:00 2001 From: Chao Yu chao@kernel.org Date: Thu, 21 Nov 2024 22:17:16 +0800 Subject: [PATCH] f2fs: fix to drop all discards after creating snapshot on lvm device

Piergiorgio reported a bug in bugzilla as below:

------------[ cut here ]------------ WARNING: CPU: 2 PID: 969 at fs/f2fs/segment.c:1330 RIP: 0010:__submit_discard_cmd+0x27d/0x400 [f2fs] Call Trace: __issue_discard_cmd+0x1ca/0x350 [f2fs] issue_discard_thread+0x191/0x480 [f2fs] kthread+0xcf/0x100 ret_from_fork+0x31/0x50 ret_from_fork_asm+0x1a/0x30

w/ below testcase, it can reproduce this bug quickly: - pvcreate /dev/vdb - vgcreate myvg1 /dev/vdb - lvcreate -L 1024m -n mylv1 myvg1 - mount /dev/myvg1/mylv1 /mnt/f2fs - dd if=/dev/zero of=/mnt/f2fs/file bs=1M count=20 - sync - rm /mnt/f2fs/file - sync - lvcreate -L 1024m -s -n mylv1-snapshot /dev/myvg1/mylv1 - umount /mnt/f2fs

The root cause is: it will update discard_max_bytes of mounted lvm device to zero after creating snapshot on this lvm device, then, __submit_discard_cmd() will pass parameter @nr_sects w/ zero value to __blkdev_issue_discard(), it returns a NULL bio pointer, result in panic.

This patch changes as below for fixing: 1. Let's drop all remained discards in f2fs_unfreeze() if snapshot of lvm device is created. 2. Checking discard_max_bytes before submitting discard during __submit_discard_cmd().

Cc: stable@vger.kernel.org Fixes: 35ec7d574884 ("f2fs: split discard command in prior to block layer") Reported-by: Piergiorgio Sartor piergiorgio.sartor@nexgo.de Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219484 Signed-off-by: Chao Yu chao@kernel.org Signed-off-by: Jaegeuk Kim jaegeuk@kernel.org

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c index 4236040e3994..eade36c5ef13 100644 --- a/fs/f2fs/segment.c +++ b/fs/f2fs/segment.c @@ -1290,16 +1290,18 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi, 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

+ /* + * stop issuing discard for any of below cases: + * 1. device is conventional zone, but it doesn't support discard. + * 2. device is regulare device, after snapshot it doesn't support + * discard. + */ + if (!bdev_max_discard_sectors(bdev)) + return -EOPNOTSUPP; + trace_f2fs_issue_discard(bdev, dc->di.start, dc->di.len);

lstart = dc->di.lstart; diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c index c0670cd61956..fc7d463dee15 100644 --- a/fs/f2fs/super.c +++ b/fs/f2fs/super.c @@ -1760,6 +1760,18 @@ static int f2fs_freeze(struct super_block *sb)

static int f2fs_unfreeze(struct super_block *sb) { + struct f2fs_sb_info *sbi = F2FS_SB(sb); + + /* + * It will update discard_max_bytes of mounted lvm device to zero + * after creating snapshot on this lvm device, let's drop all + * remained discards. + * We don't need to disable real-time discard because discard_max_bytes + * will recover after removal of snapshot. + */ + if (test_opt(sbi, DISCARD) && !f2fs_hw_support_discard(sbi)) + f2fs_issue_discard_timeout(sbi); + clear_sbi_flag(F2FS_SB(sb), SBI_IS_FREEZING); return 0; }