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[v2,4/4] btrfs: assert that relocation is protected with sb_start_write()

Message ID 3f88d51b35da92bf2391febd7186973cc9539e95.1647436353.git.naohiro.aota@wdc.com (mailing list archive)
State New, archived
Headers show
Series protect relocation with sb_start_write | expand

Commit Message

Naohiro Aota March 16, 2022, 1:22 p.m. UTC 
btrfs_relocate_chunk() initiates new ordered extents. They can cause a
hang when a process is trying to thaw the filesystem.

We should have called sb_start_write(), so the filesystem is not being
frozen. Add an ASSERT to check it is protected.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
---
 fs/btrfs/volumes.c | 3 +++
 1 file changed, 3 insertions(+)
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Patch

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 3471698fd831..393fc7db99d3 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3230,6 +3230,9 @@  int btrfs_relocate_chunk(struct btrfs_fs_info *fs_info, u64 chunk_offset)
 	u64 length;
 	int ret;
 
+	/* Assert we called sb_start_write(), not to race with FS freezing */
+	ASSERT(sb_write_started(fs_info->sb));
+
 	if (btrfs_fs_incompat(fs_info, EXTENT_TREE_V2)) {
 		btrfs_err(fs_info,
 			  "relocate: not supported on extent tree v2 yet");