[Devel] [PATCH vz7] fuse: relax i_mutex coverage in fuse_fsync

[Denis V. Lunev]

On 11/30/2016 04:02 AM, Maxim Patlasov wrote:
> fuse_fsync_common() does need i_mutex for fuse_sync_writes() and
> fuse_flush_mtime(). But when those operations are done, it's actually
> doesn't matter whether to hold the lock over fuse_request_send(FUSE_FSYNC)
> or not: we ensured that all relevant data were already seen by
> userspace fuse daemon, and so it will sync them (by handling FUSE_FSYNC)
> anyway; if the user screws up by leaking new data updates in-between, it
> is up to the user and doesn't violate fsync(2) semantics.
>
> https://jira.sw.ru/browse/PSBM-55919
>
> Signed-off-by: Maxim Patlasov <mpatlasov at virtuozzo.com>
Can you pls think about merging the same into PCS6-Up12?


> ---
>  fs/fuse/file.c |    3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 464b2f5..559dfd9 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -697,6 +697,8 @@ int fuse_fsync_common(struct file *file, loff_t start, loff_t end,
>  		goto out;
>  	}
>  
> +	mutex_unlock(&inode->i_mutex);
> +
>  	memset(&inarg, 0, sizeof(inarg));
>  	inarg.fh = ff->fh;
>  	inarg.fsync_flags = datasync ? 1 : 0;
> @@ -715,6 +717,7 @@ int fuse_fsync_common(struct file *file, loff_t start, loff_t end,
>  			fc->no_fsync = 1;
>  		err = 0;
>  	}
> +	return err;
>  out:
>  	mutex_unlock(&inode->i_mutex);
>  	return err;
>