Messages in this thread | | | Subject | Re: [PATCH] NFSD: fix wrong mnt_writer count in rename (MMOTM 2007-11-10-19-05) | From | Dave Hansen <> | Date | Tue, 13 Nov 2007 09:39:41 -0800 |
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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 <ezk@cs.sunysb.edu> > > 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 <haveblue@us.ibm.com>
-- Dave
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