On 10/19/2013 12:32, Shilong Wang wrote:
2013/10/19, Stefan Behrens <[email protected]>:
On 10/19/2013 06:17, Wang Shilong wrote:
From: Wang Shilong <[email protected]>
Scrubing supers is not in a transaction context, when trying to
write supers to disk, we should check if we are trying to
scrub supers.Fix it.
Signed-off-by: Wang Shilong <[email protected]>
---
fs/btrfs/disk-io.c | 2 ++
fs/btrfs/transaction.c | 2 ++
2 files changed, 4 insertions(+)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 419968e..0debb19 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3582,7 +3582,9 @@ int btrfs_commit_super(struct btrfs_root *root)
return ret;
}
+ btrfs_scrub_pause_super(root);
ret = write_ctree_super(NULL, root, 0);
+ btrfs_scrub_continue_super(root);
return ret;
}
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 277fe81..3ebcbbd 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1892,7 +1892,9 @@ int btrfs_commit_transaction(struct
btrfs_trans_handle *trans,
goto cleanup_transaction;
}
+ btrfs_scrub_pause_super(root);
ret = write_ctree_super(trans, root, 0);
+ btrfs_scrub_continue_super(root);
if (ret) {
mutex_unlock(&root->fs_info->tree_log_mutex);
goto cleanup_transaction;
What kind of race do you see between writing the 4K superblock and scrub
checking its checksum? Or in other words, what could happen?
> Yeah, it did not hurt. but it may output checksum mismatch. For
example:
> Writing 4k superblock is not totally finished, but we are trying to
scrub it.
Have you ever seen this issue?
If yes, let's find a different solution. You scrub, let's say, once a
week. Scrubbing the superblock takes, let's say, 100ms, then it's
finished. This short race doesn't justify to add such code to
btrfs_commit_transaction and btrfs_commit_super IMHO. And commiting a
transaction is synchronized to scrub already when the commit root is
updated.
If this is really an issue and these 4K disk writes and reads interfere,
let's find a better solution please.
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