From: Anand Jain <anand.jain@oracle.com>
To: linux-btrfs@vger.kernel.org
Cc: Anand Jain <anand.jain@oracle.com>,
Chris Murphy <lists@colorremedies.com>
Subject: [PATCH] btrfs: fix unmountable seed device after fstrim
Date: Fri, 30 Apr 2021 17:10:28 +0800 [thread overview]
Message-ID: <c7715d09a67f212e0ecb5fea2d598513912092f4.1619443900.git.anand.jain@oracle.com> (raw)
The following test case reproduces an issue of wrongly freeing the in-use
block on the readonly seed device when fstrim is called on the rw sprout
device. As shown below.
create a seed device and add a sprout device to it
mkfs.btrfs -fq -dsingle -msingle /dev/loop0
btrfstune -S 1 /dev/loop0
mount /dev/loop0 /btrfs
btrfs dev add -f /dev/loop1 /btrfs
BTRFS info (device loop0): relocating block group 290455552 flags system
BTRFS info (device loop0): relocating block group 1048576 flags system
BTRFS info (device loop0): disk added /dev/loop1
umount /btrfs
mount the sprout device and run fstrim
mount /dev/loop1 /btrfs
fstrim /btrfs
umount /btrfs
now try to mount the seed device, and it fails...
mount /dev/loop0 /btrfs
mount: /btrfs: wrong fs type, bad option, bad superblock on /dev/loop0, missing codepage or helper program, or other error.
BTRFS error (device loop0): bad tree block start, want 5292032 have 0
BTRFS warning (device loop0): couldn't read-tree root
BTRFS error (device loop0): open_ctree failed
Block 5292032 is missing on the readonly seed device.
From the dump-tree of the seed device taken before the fstrim. Block
5292032 belonged to the block group starting at 5242880
<snip>
item 3 key (5242880 BLOCK_GROUP_ITEM 8388608) itemoff 16169 itemsize 24
block group used 114688 chunk_objectid 256 flags METADATA
<snip>
From the dump-tree of the sprout device (taken before the fstrim).
fstrim used the block-group 5242880 to find the free space to free.
<snip>
item 1 key (5242880 BLOCK_GROUP_ITEM 8388608) itemoff 16226 itemsize 24
block group used 32768 chunk_objectid 256 flags METADATA
<snip>
bpf tracing the fstrim command finds the missing block 5292032 within the
range of the discarded blocks...
kprobe:btrfs_discard_extent {
printf("free start %llu end %llu num_bytes %llu\n", arg1, arg1+arg2, arg2);
}
btrfs_discard_extent(..., start, num_bytes, ...):
free start 5259264 end 5406720 num_bytes 147456
<snip>
Fix this by avoiding the discard command to the readonly seed device.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reported-by: Chris Murphy <lists@colorremedies.com>
---
A xfstests case to follow.
fs/btrfs/extent-tree.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 7a28314189b4..0d19bd213715 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1340,12 +1340,19 @@ int btrfs_discard_extent(struct btrfs_fs_info *fs_info, u64 bytenr,
stripe = bbio->stripes;
for (i = 0; i < bbio->num_stripes; i++, stripe++) {
u64 bytes;
+ struct btrfs_device *device = stripe->dev;
- if (!stripe->dev->bdev) {
+ if (!device->bdev) {
ASSERT(btrfs_test_opt(fs_info, DEGRADED));
continue;
}
+ /*
+ * Skip sending discard command to a non-writeable device.
+ */
+ if (!test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state))
+ continue;
+
ret = do_discard_extent(stripe, &bytes);
if (!ret) {
discarded_bytes += bytes;
--
2.29.2
next reply other threads:[~2021-04-30 9:10 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-30 9:10 Anand Jain [this message]
2021-04-30 10:11 ` [PATCH] btrfs: fix unmountable seed device after fstrim Filipe Manana
2021-04-30 11:06 ` Anand Jain
2021-04-30 11:59 ` Anand Jain
2021-04-30 12:14 ` Filipe Manana
2021-04-30 12:48 ` Anand Jain
2021-05-03 13:34 ` David Sterba
2021-04-30 14:39 ` [PATCH] btrfs: add fstrim test case on the sprout device Anand Jain
2021-04-30 15:24 ` Filipe Manana
2021-05-01 5:16 ` Anand Jain
2021-05-01 5:17 ` [PATCH v2] " Anand Jain
2021-05-03 9:54 ` Filipe Manana
2021-05-03 10:29 ` Anand Jain
2021-05-03 11:08 ` [PATCH v3] " Anand Jain
2021-05-03 11:16 ` Filipe Manana
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