On Mon, 2007-11-12 at 20:15 -0500, Erez Zadok wrote:
> NFSD forgets to call mnt_drop_write after a successful rename. Here's a
> fix. (Ah, the curse of a stackable file system developer: you have to debug
> everyone else's too. :-)
>
> One thing I wasn't sure is whether I could move the mnt_drop_write line a
> little above, just after the call to vfs_rename. If we can drop the ref
> earlier, it could improve scalability/performance just a bit, no? (i.e.,
> what are the ramifications of holding on to this mnt writer ref longer than
> needed?)
I do see some write-ish things happening inside of the nfsd_sync_dir()
call chain: the fsync() and filemap_fdatawrite().
The danger here is that the moment you mnt_drop_write(), the filesystem
is mounted r/o by someone else, then those fsync() writes occur when
everyone thinks it is r/o. So, I think your fix is the most
conservative, and the most correct.
> Signed-off-by: Erez Zadok <[email protected]>
>
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index 7dfde65..47aec49 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -1693,6 +1693,7 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
> if (!host_err)
> host_err = nfsd_sync_dir(fdentry);
> }
> + mnt_drop_write(ffhp->fh_export->ex_path.mnt);
>
> out_dput_new:
> dput(ndentry);
Otherwise, looks good to me. Thanks.
Signed-off-by: Dave Hansen <[email protected]>
-- Dave
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