[PATCH 5.15 075/171] btrfs: free exchange changeset on failures

Greg Kroah-Hartman
2021-12-13T10:21:13Z

From: Johannes Thumshirn <johannes.thumshirn@wdc.com>

commit da5e817d9d75422eaaa05490d0b9a5e328fc1a51 upstream.

Fstests runs on my VMs have show several kmemleak reports like the following.

unreferenced object 0xffff88811ae59080 (size 64):
comm "xfs_io", pid 12124, jiffies 4294987392 (age 6.368s)
hex dump (first 32 bytes):
00 c0 1c 00 00 00 00 00 ff cf 1c 00 00 00 00 00 ................
90 97 e5 1a 81 88 ff ff 90 97 e5 1a 81 88 ff ff ................
backtrace:
[<00000000ac0176d2>] ulist_add_merge+0x60/0x150 [btrfs]
[<0000000076e9f312>] set_state_bits+0x86/0xc0 [btrfs]
[<0000000014fe73d6>] set_extent_bit+0x270/0x690 [btrfs]
[<000000004f675208>] set_record_extent_bits+0x19/0x20 [btrfs]
[<00000000b96137b1>] qgroup_reserve_data+0x274/0x310 [btrfs]
[<0000000057e9dcbb>] btrfs_check_data_free_space+0x5c/0xa0 [btrfs]
[<0000000019c4511d>] btrfs_delalloc_reserve_space+0x1b/0xa0 [btrfs]
[<000000006d37e007>] btrfs_dio_iomap_begin+0x415/0x970 [btrfs]
[<00000000fb8a74b8>] iomap_iter+0x161/0x1e0
[<0000000071dff6ff>] __iomap_dio_rw+0x1df/0x700
[<000000002567ba53>] iomap_dio_rw+0x5/0x20
[<0000000072e555f8>] btrfs_file_write_iter+0x290/0x530 [btrfs]
[<000000005eb3d845>] new_sync_write+0x106/0x180
[<000000003fb505bf>] vfs_write+0x24d/0x2f0
[<000000009bb57d37>] __x64_sys_pwrite64+0x69/0xa0
[<000000003eba3fdf>] do_syscall_64+0x43/0x90

In case brtfs_qgroup_reserve_data() or btrfs_delalloc_reserve_metadata()
fail the allocated extent_changeset will not be freed.

So in btrfs_check_data_free_space() and btrfs_delalloc_reserve_space()
free the allocated extent_changeset to get rid of the allocated memory.

The issue currently only happens in the direct IO write path, but only
after 65b3c08606e5 ("btrfs: fix ENOSPC failure when attempting direct IO
write into NOCOW range"), and also at defrag_one_locked_target(). Every
other place is always calling extent_changeset_free() even if its call
to btrfs_delalloc_reserve_space() or btrfs_check_data_free_space() has
failed.

CC: stable@vger.kernel.org # 5.15+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/btrfs/delalloc-space.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

--- a/fs/btrfs/delalloc-space.c
+++ b/fs/btrfs/delalloc-space.c
@@ -143,10 +143,13 @@ int btrfs_check_data_free_space(struct b

/* Use new btrfs_qgroup_reserve_data to reserve precious data space. */
ret = btrfs_qgroup_reserve_data(inode, reserved, start, len);
- if (ret < 0)
+ if (ret < 0) {
btrfs_free_reserved_data_space_noquota(fs_info, len);
- else
+ extent_changeset_free(*reserved);
+ *reserved = NULL;
+ } else {
ret = 0;
+ }
return ret;
}

@@ -452,8 +455,11 @@ int btrfs_delalloc_reserve_space(struct
if (ret < 0)
return ret;
ret = btrfs_delalloc_reserve_metadata(inode, len);
- if (ret < 0)
+ if (ret < 0) {
btrfs_free_reserved_data_space(inode, *reserved, start, len);
+ extent_changeset_free(*reserved);
+ *reserved = NULL;
+ }
return ret;
}