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    SubjectRe: [PATCH 08/11] vfs: Merge check_submounts_and_drop and d_invalidate
    On Sat, Feb 15, 2014 at 01:39:22PM -0800, Eric W. Biederman wrote:
    >
    > Now that d_invalidate is the only caller of check_submounts_and_drop,
    > expand check_submounts_and_drop inline in d_invalidate.
    >
    > Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
    > ---
    > fs/dcache.c | 55 +++++++++++++++++++----------------------------
    > include/linux/dcache.h | 1 -
    > 2 files changed, 22 insertions(+), 34 deletions(-)
    >
    > diff --git a/fs/dcache.c b/fs/dcache.c
    > index 27585b1dd6f1..5b41205cbf33 100644
    > --- a/fs/dcache.c
    > +++ b/fs/dcache.c
    > @@ -608,32 +608,6 @@ kill_it:
    > }
    > EXPORT_SYMBOL(dput);
    >
    > -/**
    > - * d_invalidate - invalidate a dentry
    > - * @dentry: dentry to invalidate
    > - *
    > - * Try to invalidate the dentry if it turns out to be
    > - * possible. If there are reasons not to delete it
    > - * return -EBUSY. On success return 0.
    > - *
    > - * no dcache lock.
    > - */
    > -
    > -int d_invalidate(struct dentry * dentry)
    > -{
    > - /*
    > - * If it's already been dropped, return OK.
    > - */
    > - spin_lock(&dentry->d_lock);
    > - if (d_unhashed(dentry)) {
    > - spin_unlock(&dentry->d_lock);
    > - return 0;
    > - }
    > - spin_unlock(&dentry->d_lock);
    > -
    > - return check_submounts_and_drop(dentry);
    > -}
    > -EXPORT_SYMBOL(d_invalidate);
    >
    > /* This must be called with d_lock held */
    > static inline void __dget_dlock(struct dentry *dentry)
    > @@ -1175,7 +1149,7 @@ EXPORT_SYMBOL(have_submounts);
    > * reachable (e.g. NFS can unhash a directory dentry and then the complete
    > * subtree can become unreachable).
    > *
    > - * Only one of check_submounts_and_drop() and d_set_mounted() must succeed. For
    > + * Only one of d_invalidate() and d_set_mounted() must succeed. For
    > * this reason take rename_lock and d_lock on dentry and ancestors.
    > */
    > int d_set_mounted(struct dentry *dentry)
    > @@ -1184,7 +1158,7 @@ int d_set_mounted(struct dentry *dentry)
    > int ret = -ENOENT;
    > write_seqlock(&rename_lock);
    > for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
    > - /* Need exclusion wrt. check_submounts_and_drop() */
    > + /* Need exclusion wrt. d_invalidate() */
    > spin_lock(&p->d_lock);
    > if (unlikely(d_unhashed(p))) {
    > spin_unlock(&p->d_lock);
    > @@ -1400,18 +1374,33 @@ static void check_and_drop(void *_data)
    > }
    >
    > /**
    > - * check_submounts_and_drop - detach submounts, prune dcache, and drop
    > + * d_invalidate - detach submounts, prune dcache, and drop
    > + * @dentry: dentry to invalidate (aka detach, prune and drop)
    > + *
    > + * Try to invalidate the dentry if it turns out to be
    > + * possible. If there are reasons not to delete it
    > + * return -EBUSY. On success return 0.
    > + *
    > + * no dcache lock.
    > *
    > * The final d_drop is done as an atomic operation relative to
    > * rename_lock ensuring there are no races with d_set_mounted. This
    > * ensures there are no unhashed dentries on the path to a mountpoint.
    > - *
    > - * @dentry: dentry to detach, prune and drop
    > */
    > -int check_submounts_and_drop(struct dentry *dentry)
    > +int d_invalidate(struct dentry *dentry)
    > {
    > int ret = 0;
    >
    > + /*
    > + * If it's already been dropped, return OK.
    > + */
    > + spin_lock(&dentry->d_lock);
    > + if (d_unhashed(dentry)) {
    > + spin_unlock(&dentry->d_lock);
    > + return 0;
    > + }
    > + spin_unlock(&dentry->d_lock);
    > +
    > /* Negative dentries can be dropped without further checks */
    > if (!dentry->d_inode) {
    > d_drop(dentry);


    You can optimize this by including the negative check within the above d_locked
    region and calling __d_drop() instead.

    > @@ -1445,7 +1434,7 @@ int check_submounts_and_drop(struct dentry *dentry)
    > out:
    > return ret;
    > }
    > -EXPORT_SYMBOL(check_submounts_and_drop);
    > +EXPORT_SYMBOL(d_invalidate);
    >
    > /**
    > * __d_alloc - allocate a dcache entry
    > diff --git a/include/linux/dcache.h b/include/linux/dcache.h
    > index bf72e9ac6de0..ae77222c3e86 100644
    > --- a/include/linux/dcache.h
    > +++ b/include/linux/dcache.h
    > @@ -265,7 +265,6 @@ extern void d_prune_aliases(struct inode *);
    >
    > /* test whether we have any submounts in a subdir tree */
    > extern int have_submounts(struct dentry *);
    > -extern int check_submounts_and_drop(struct dentry *);
    >
    > /*
    > * This adds the entry to the hash queues.
    > --
    > 1.7.5.4
    >


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