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@xxxxxxxxxxxxxxx
Fixes: 35ec7d574884 ("f2fs: split discard command in prior to block layer")
Reported-by: Piergiorgio Sartor <piergiorgio.sartor@xxxxxxxx>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219484
Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
---
fs/f2fs/segment.c | 16 +++++++++-------
fs/f2fs/super.c | 12 ++++++++++++
2 files changed, 21 insertions(+), 7 deletions(-)
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 7bdfe08ce9ea..af3fb3f6d9b5 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;
}
--
2.40.1
