Hi Al,
We'd like to get this into mainline during this window. Does this patch
look good to you?
Thanks-
sage
On Wed, 21 Aug 2013, Sage Weil wrote:
> On Tue, 13 Aug 2013, Yan, Zheng wrote:
> > From: "Yan, Zheng" <zheng.z.yan@xxxxxxxxx>
> >
> > The d_prune dentry operation is used to notify filesystem when VFS
> > about to prune a hashed dentry from the dcache. There are three
> > code paths that prune dentries: shrink_dcache_for_umount_subtree(),
> > prune_dcache_sb() and d_prune_aliases(). For the d_prune_aliases()
> > case, VFS unhashes the dentry first, then call the d_prune dentry
> > operation. This confuses ceph_d_prune() (ceph uses the d_prune
> > dentry operation to maintain a flag indicating whether the complete
> > contents of a directory are in the dcache, pruning unhashed dentry
> > does not affect dir's completeness)
> >
> > This patch fixes the issue by calling the d_prune dentry operation
> > in d_prune_aliases(), before unhashing the dentry. Also make VFS
> > only call the d_prune dentry operation for hashed dentry, to avoid
> > calling the d_prune dentry operation twice when dentry is pruned
> > by d_prune_aliases().
> >
> > Signed-off-by: Yan, Zheng <zheng.z.yan@xxxxxxxxx>
>
> Reviewed-by: Sage Weil <sage@xxxxxxxxxxx>
>
> This is behaving well under my testing, seems to resolve the race we were
> encoutering before, and cleans up the d_prune semantics nicely IMO.
>
> Al, does this look okay to you?
>
> Thanks!
> sage
>
> > ---
> > fs/dcache.c | 13 +++++++++++--
> > 1 file changed, 11 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/dcache.c b/fs/dcache.c
> > index 87bdb53..612e99b 100644
> > --- a/fs/dcache.c
> > +++ b/fs/dcache.c
> > @@ -472,7 +472,7 @@ relock:
> > * inform the fs via d_prune that this dentry is about to be
> > * unhashed and destroyed.
> > */
> > - if (dentry->d_flags & DCACHE_OP_PRUNE)
> > + if ((dentry->d_flags & DCACHE_OP_PRUNE) && !d_unhashed(dentry))
> > dentry->d_op->d_prune(dentry);
> >
> > dentry_lru_del(dentry);
> > @@ -719,6 +719,14 @@ restart:
> > hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) {
> > spin_lock(&dentry->d_lock);
> > if (!dentry->d_count) {
> > + /*
> > + * inform the fs via d_prune that this dentry
> > + * is about to be unhashed and destroyed.
> > + */
> > + if ((dentry->d_flags & DCACHE_OP_PRUNE) &&
> > + !d_unhashed(dentry))
> > + dentry->d_op->d_prune(dentry);
> > +
> > __dget_dlock(dentry);
> > __d_drop(dentry);
> > spin_unlock(&dentry->d_lock);
> > @@ -907,7 +915,8 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
> > * inform the fs that this dentry is about to be
> > * unhashed and destroyed.
> > */
> > - if (dentry->d_flags & DCACHE_OP_PRUNE)
> > + if ((dentry->d_flags & DCACHE_OP_PRUNE) &&
> > + !d_unhashed(dentry))
> > dentry->d_op->d_prune(dentry);
> >
> > dentry_lru_del(dentry);
> > --
> > 1.8.1.4
> >
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