dentry_kill(): don't try to remove from shrink list

If the victim in on the shrink list, don't remove it from there.
If shrink_dentry_list() manages to remove it from the list before
we are done - fine, we'll just free it as usual.  If not - mark
it with new flag (DCACHE_MAY_FREE) and leave it there.

Eventually, shrink_dentry_list() will get to it, remove the sucker
from shrink list and call dentry_kill(dentry, 0).  Which is where
we'll deal with freeing.

Since now dentry_kill(dentry, 0) may happen after or during
dentry_kill(dentry, 1), we need to recognize that (by seeing
DCACHE_DENTRY_KILLED already set), unlock everything
and either free the sucker (in case DCACHE_MAY_FREE has been
set) or leave it for ongoing dentry_kill(dentry, 1) to deal with.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/dcache.c b/fs/dcache.c
index e482775343a0d3fe6d518e257286b08bc3b56da8..58e26bee7ef463fe36f3f7ecbc84b7dfd1a34134 100644 (file)
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -468,7 +468,14 @@ dentry_kill(struct dentry *dentry, int unlock_on_failure)
        __releases(dentry->d_lock)
 {
        struct inode *inode;
-       struct dentry *parent;
+       struct dentry *parent = NULL;
+       bool can_free = true;
+
+       if (unlikely(dentry->d_flags & DCACHE_DENTRY_KILLED)) {
+               can_free = dentry->d_flags & DCACHE_MAY_FREE;
+               spin_unlock(&dentry->d_lock);
+               goto out;
+       }
 
        inode = dentry->d_inode;
        if (inode && !spin_trylock(&inode->i_lock)) {
@@ -479,9 +486,7 @@ relock:
                }
                return dentry; /* try again with same dentry */
        }
-       if (IS_ROOT(dentry))
-               parent = NULL;
-       else
+       if (!IS_ROOT(dentry))
                parent = dentry->d_parent;
        if (parent && !spin_trylock(&parent->d_lock)) {
                if (inode)
@@ -504,8 +509,6 @@ relock:
        if (dentry->d_flags & DCACHE_LRU_LIST) {
                if (!(dentry->d_flags & DCACHE_SHRINK_LIST))
                        d_lru_del(dentry);
-               else
-                       d_shrink_del(dentry);
        }
        /* if it was on the hash then remove it */
        __d_drop(dentry);
@@ -527,7 +530,15 @@ relock:
        if (dentry->d_op && dentry->d_op->d_release)
                dentry->d_op->d_release(dentry);
 
-       dentry_free(dentry);
+       spin_lock(&dentry->d_lock);
+       if (dentry->d_flags & DCACHE_SHRINK_LIST) {
+               dentry->d_flags |= DCACHE_MAY_FREE;
+               can_free = false;
+       }
+       spin_unlock(&dentry->d_lock);
+out:
+       if (likely(can_free))
+               dentry_free(dentry);
        return parent;
 }
 
@@ -829,7 +840,7 @@ static void shrink_dentry_list(struct list_head *list)
                 * We found an inuse dentry which was not removed from
                 * the LRU because of laziness during lookup. Do not free it.
                 */
-               if (dentry->d_lockref.count) {
+               if ((int)dentry->d_lockref.count > 0) {
                        spin_unlock(&dentry->d_lock);
                        continue;
                }

diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 3b9bfdb83ba6f698cbe1ddf8409f8b6e0dc17427..3c7ec327ebd2eecc2fb63ac4f742ca0d75c56ec8 100644 (file)
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -221,6 +221,8 @@ struct dentry_operations {
 #define DCACHE_SYMLINK_TYPE            0x00300000 /* Symlink */
 #define DCACHE_FILE_TYPE               0x00400000 /* Other file type */
 
+#define DCACHE_MAY_FREE                        0x00800000
+
 extern seqlock_t rename_lock;
 
 static inline int dname_external(const struct dentry *dentry)