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 4236040e3994cc74948b6908fc36539d10e93743..eade36c5ef138ce5814eb1ff4fce27a72f3224fd 100644 (file)
--- 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 c0670cd61956301d3ddbebe42c45605a619f6cc5..fc7d463dee158ac6aeb7d101492b56e0045636cc 100644 (file)
--- 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;
 }