From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
commit 41edf278fc2f042f4e22a12ed87d19c5201210e1 upstream.
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@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
fs/dcache.c | 27 +++++++++++++++++++--------
include/linux/dcache.h | 2 ++
2 files changed, 21 insertions(+), 8 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index 2bb4e4f1ca6d..8647519e864a 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -490,7 +490,14 @@ 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)) {
@@ -501,9 +508,7 @@ 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)
@@ -526,8 +531,6 @@ 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);
@@ -549,7 +552,15 @@ 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;
}
@@ -851,7 +862,7 @@ 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 59066e0b4ff1..cbde0540d4dd 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -211,6 +211,8 @@ struct dentry_operations {
#define DCACHE_LRU_LIST 0x80000
#define DCACHE_DENTRY_KILLED 0x100000
+#define DCACHE_MAY_FREE 0x00800000
+
extern seqlock_t rename_lock;
static inline int dname_external(const struct dentry *dentry)
--
2.1.2
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