diff --git a/fs/9p/acl.c b/fs/9p/acl.c
index 9da967f383872dab4bc08ed149a230f5f8304f1a..2d94e94b6b591277753e0f7f8dd66663fa0db1ed 100644
--- a/fs/9p/acl.c
+++ b/fs/9p/acl.c
@@ -93,7 +93,7 @@ static struct posix_acl *v9fs_get_cached_acl(struct inode *inode, int type)
* instantiating the inode (v9fs_inode_from_fid)
*/
acl = get_cached_acl(inode, type);
- BUG_ON(acl == ACL_NOT_CACHED);
+ BUG_ON(is_uncached_acl(acl));
return acl;
}
diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
index 6d263bb1621cd92c51cc6ebd014f8ad06dcd719f..67a607709d4f7eb18d941cf1a70c7d00a7afba66 100644
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -63,9 +63,6 @@ struct posix_acl *btrfs_get_acl(struct inode *inode, int type)
}
kfree(value);
- if (!IS_ERR(acl))
- set_cached_acl(inode, type, acl);
-
return acl;
}
diff --git a/fs/ceph/acl.c b/fs/ceph/acl.c
index f19708487e2f74c80e55b14ecbadb07bf79b73a9..5457f216e2e5bc4999eb4795cee994b941a57365 100644
--- a/fs/ceph/acl.c
+++ b/fs/ceph/acl.c
@@ -37,6 +37,8 @@ static inline void ceph_set_cached_acl(struct inode *inode,
spin_lock(&ci->i_ceph_lock);
if (__ceph_caps_issued_mask(ci, CEPH_CAP_XATTR_SHARED, 0))
set_cached_acl(inode, type, acl);
+ else
+ forget_cached_acl(inode, type);
spin_unlock(&ci->i_ceph_lock);
}
diff --git a/fs/ext2/acl.c b/fs/ext2/acl.c
index 27695e6f4e46629a8a888f38bcaf6f0e4ceaf1ec..42f1d1814083c568cff9b6daf181d96da1ac5420 100644
--- a/fs/ext2/acl.c
+++ b/fs/ext2/acl.c
@@ -172,9 +172,6 @@ ext2_get_acl(struct inode *inode, int type)
acl = ERR_PTR(retval);
kfree(value);
- if (!IS_ERR(acl))
- set_cached_acl(inode, type, acl);
-
return acl;
}
diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c
index 69b1e73026a51f6b8ae0e591d33abb0fdc9169d8..c6601a476c021f52235350666fc82f9424f87464 100644
--- a/fs/ext4/acl.c
+++ b/fs/ext4/acl.c
@@ -172,9 +172,6 @@ ext4_get_acl(struct inode *inode, int type)
acl = ERR_PTR(retval);
kfree(value);
- if (!IS_ERR(acl))
- set_cached_acl(inode, type, acl);
-
return acl;
}
diff --git a/fs/f2fs/acl.c b/fs/f2fs/acl.c
index c8f25f7241f06a96c3d99ebf5c82e53a6099ed60..6f1fdda977b396839d7804fc4fcdb4a948895b53 100644
--- a/fs/f2fs/acl.c
+++ b/fs/f2fs/acl.c
@@ -190,9 +190,6 @@ static struct posix_acl *__f2fs_get_acl(struct inode *inode, int type,
acl = ERR_PTR(retval);
kfree(value);
- if (!IS_ERR(acl))
- set_cached_acl(inode, type, acl);
-
return acl;
}
diff --git a/fs/hfsplus/posix_acl.c b/fs/hfsplus/posix_acl.c
index afb33eda6d7dbae7ea5dab4d19b1edc401db151a..ab7ea2506b4defa4ff126fe19762e9d6157ef893 100644
--- a/fs/hfsplus/posix_acl.c
+++ b/fs/hfsplus/posix_acl.c
@@ -48,9 +48,6 @@ struct posix_acl *hfsplus_get_posix_acl(struct inode *inode, int type)
hfsplus_destroy_attr_entry((hfsplus_attr_entry *)value);
- if (!IS_ERR(acl))
- set_cached_acl(inode, type, acl);
-
return acl;
}
diff --git a/fs/inode.c b/fs/inode.c
index 69b8b526c1946c455c8b5ad0c8939542d9c2e82d..4202aac99464079e89609a492fb0c514a0af8a7c 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -238,9 +238,9 @@ void __destroy_inode(struct inode *inode)
}
#ifdef CONFIG_FS_POSIX_ACL
- if (inode->i_acl && inode->i_acl != ACL_NOT_CACHED)
+ if (inode->i_acl && !is_uncached_acl(inode->i_acl))
posix_acl_release(inode->i_acl);
- if (inode->i_default_acl && inode->i_default_acl != ACL_NOT_CACHED)
+ if (inode->i_default_acl && !is_uncached_acl(inode->i_default_acl))
posix_acl_release(inode->i_default_acl);
#endif
this_cpu_dec(nr_inodes);
diff --git a/fs/jffs2/acl.c b/fs/jffs2/acl.c
index 2f7a3c09048999f4365c3e5612ffdf18e9c65d54..bc2693d562987a6602b9403599f48d6c481a39be 100644
--- a/fs/jffs2/acl.c
+++ b/fs/jffs2/acl.c
@@ -203,8 +203,6 @@ struct posix_acl *jffs2_get_acl(struct inode *inode, int type)
acl = ERR_PTR(rc);
}
kfree(value);
- if (!IS_ERR(acl))
- set_cached_acl(inode, type, acl);
return acl;
}
diff --git a/fs/jfs/acl.c b/fs/jfs/acl.c
index ab4882801b24393470f301a4b990f1399b0f87e2..21fa92ba2c191664fb2851da022f76a5e5d62388 100644
--- a/fs/jfs/acl.c
+++ b/fs/jfs/acl.c
@@ -63,8 +63,6 @@ struct posix_acl *jfs_get_acl(struct inode *inode, int type)
acl = posix_acl_from_xattr(&init_user_ns, value, size);
}
kfree(value);
- if (!IS_ERR(acl))
- set_cached_acl(inode, type, acl);
return acl;
}
diff --git a/fs/namei.c b/fs/namei.c
index 794f81dce76606ec025e3dcf1f182a175eaa0e82..3498d53de26fe4e33aa0620f4cd5fcfb3f208149 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -265,7 +265,7 @@ static int check_acl(struct inode *inode, int mask)
if (!acl)
return -EAGAIN;
/* no ->get_acl() calls in RCU mode... */
- if (acl == ACL_NOT_CACHED)
+ if (is_uncached_acl(acl))
return -ECHILD;
return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
}
diff --git a/fs/nfs/nfs3acl.c b/fs/nfs/nfs3acl.c
index 17c0fa1eccfaad22710fe6e938dc4904cc5b8cdf..720d92f5abfb838875bb1a01630e101e4738581a 100644
--- a/fs/nfs/nfs3acl.c
+++ b/fs/nfs/nfs3acl.c
@@ -11,6 +11,38 @@
#define NFSDBG_FACILITY NFSDBG_PROC
+/*
+ * nfs3_prepare_get_acl, nfs3_complete_get_acl, nfs3_abort_get_acl: Helpers for
+ * caching get_acl results in a race-free way. See fs/posix_acl.c:get_acl()
+ * for explanations.
+ */
+static void nfs3_prepare_get_acl(struct posix_acl **p)
+{
+ struct posix_acl *sentinel = uncached_acl_sentinel(current);
+
+ if (cmpxchg(p, ACL_NOT_CACHED, sentinel) != ACL_NOT_CACHED) {
+ /* Not the first reader or sentinel already in place. */
+ }
+}
+
+static void nfs3_complete_get_acl(struct posix_acl **p, struct posix_acl *acl)
+{
+ struct posix_acl *sentinel = uncached_acl_sentinel(current);
+
+ /* Only cache the ACL if our sentinel is still in place. */
+ posix_acl_dup(acl);
+ if (cmpxchg(p, sentinel, acl) != sentinel)
+ posix_acl_release(acl);
+}
+
+static void nfs3_abort_get_acl(struct posix_acl **p)
+{
+ struct posix_acl *sentinel = uncached_acl_sentinel(current);
+
+ /* Remove our sentinel upon failure. */
+ cmpxchg(p, sentinel, ACL_NOT_CACHED);
+}
+
struct posix_acl *nfs3_get_acl(struct inode *inode, int type)
{
struct nfs_server *server = NFS_SERVER(inode);
@@ -55,6 +87,11 @@ struct posix_acl *nfs3_get_acl(struct inode *inode, int type)
if (res.fattr == NULL)
return ERR_PTR(-ENOMEM);
+ if (args.mask & NFS_ACL)
+ nfs3_prepare_get_acl(&inode->i_acl);
+ if (args.mask & NFS_DFACL)
+ nfs3_prepare_get_acl(&inode->i_default_acl);
+
status = rpc_call_sync(server->client_acl, &msg, 0);
dprintk("NFS reply getacl: %d\n", status);
@@ -89,12 +126,12 @@ struct posix_acl *nfs3_get_acl(struct inode *inode, int type)
}
if (res.mask & NFS_ACL)
- set_cached_acl(inode, ACL_TYPE_ACCESS, res.acl_access);
+ nfs3_complete_get_acl(&inode->i_acl, res.acl_access);
else
forget_cached_acl(inode, ACL_TYPE_ACCESS);
if (res.mask & NFS_DFACL)
- set_cached_acl(inode, ACL_TYPE_DEFAULT, res.acl_default);
+ nfs3_complete_get_acl(&inode->i_default_acl, res.acl_default);
else
forget_cached_acl(inode, ACL_TYPE_DEFAULT);
@@ -108,6 +145,8 @@ struct posix_acl *nfs3_get_acl(struct inode *inode, int type)
}
getout:
+ nfs3_abort_get_acl(&inode->i_acl);
+ nfs3_abort_get_acl(&inode->i_default_acl);
posix_acl_release(res.acl_access);
posix_acl_release(res.acl_default);
nfs_free_fattr(res.fattr);
diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
index 474e57f834e6caff12eaca03c8ece4d35303d1e0..1eaa9100c8897a143d1409a471c4900546e94dc4 100644
--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -54,6 +54,7 @@
#include "uptodate.h"
#include "quota.h"
#include "refcounttree.h"
+#include "acl.h"
#include "buffer_head_io.h"
@@ -3623,6 +3624,8 @@ static int ocfs2_data_convert_worker(struct ocfs2_lock_res *lockres,
filemap_fdatawait(mapping);
}
+ forget_all_cached_acls(inode);
+
out:
return UNBLOCK_CONTINUE;
}
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 711dd517037689ac03fa1b31085a72ca010ab314..bc6736d6078638f6cf940f68a6a2cf08d7f5814d 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -37,14 +37,18 @@ EXPORT_SYMBOL(acl_by_type);
struct posix_acl *get_cached_acl(struct inode *inode, int type)
{
struct posix_acl **p = acl_by_type(inode, type);
- struct posix_acl *acl = ACCESS_ONCE(*p);
- if (acl) {
- spin_lock(&inode->i_lock);
- acl = *p;
- if (acl != ACL_NOT_CACHED)
- acl = posix_acl_dup(acl);
- spin_unlock(&inode->i_lock);
+ struct posix_acl *acl;
+
+ for (;;) {
+ rcu_read_lock();
+ acl = rcu_dereference(*p);
+ if (!acl || is_uncached_acl(acl) ||
+ atomic_inc_not_zero(&acl->a_refcount))
+ break;
+ rcu_read_unlock();
+ cpu_relax();
}
+ rcu_read_unlock();
return acl;
}
EXPORT_SYMBOL(get_cached_acl);
@@ -59,58 +63,72 @@ void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl)
{
struct posix_acl **p = acl_by_type(inode, type);
struct posix_acl *old;
- spin_lock(&inode->i_lock);
- old = *p;
- rcu_assign_pointer(*p, posix_acl_dup(acl));
- spin_unlock(&inode->i_lock);
- if (old != ACL_NOT_CACHED)
+
+ old = xchg(p, posix_acl_dup(acl));
+ if (!is_uncached_acl(old))
posix_acl_release(old);
}
EXPORT_SYMBOL(set_cached_acl);
-void forget_cached_acl(struct inode *inode, int type)
+static void __forget_cached_acl(struct posix_acl **p)
{
- struct posix_acl **p = acl_by_type(inode, type);
struct posix_acl *old;
- spin_lock(&inode->i_lock);
- old = *p;
- *p = ACL_NOT_CACHED;
- spin_unlock(&inode->i_lock);
- if (old != ACL_NOT_CACHED)
+
+ old = xchg(p, ACL_NOT_CACHED);
+ if (!is_uncached_acl(old))
posix_acl_release(old);
}
+
+void forget_cached_acl(struct inode *inode, int type)
+{
+ __forget_cached_acl(acl_by_type(inode, type));
+}
EXPORT_SYMBOL(forget_cached_acl);
void forget_all_cached_acls(struct inode *inode)
{
- struct posix_acl *old_access, *old_default;
- spin_lock(&inode->i_lock);
- old_access = inode->i_acl;
- old_default = inode->i_default_acl;
- inode->i_acl = inode->i_default_acl = ACL_NOT_CACHED;
- spin_unlock(&inode->i_lock);
- if (old_access != ACL_NOT_CACHED)
- posix_acl_release(old_access);
- if (old_default != ACL_NOT_CACHED)
- posix_acl_release(old_default);
+ __forget_cached_acl(&inode->i_acl);
+ __forget_cached_acl(&inode->i_default_acl);
}
EXPORT_SYMBOL(forget_all_cached_acls);
struct posix_acl *get_acl(struct inode *inode, int type)
{
+ void *sentinel;
+ struct posix_acl **p;
struct posix_acl *acl;
+ /*
+ * The sentinel is used to detect when another operation like
+ * set_cached_acl() or forget_cached_acl() races with get_acl().
+ * It is guaranteed that is_uncached_acl(sentinel) is true.
+ */
+
acl = get_cached_acl(inode, type);
- if (acl != ACL_NOT_CACHED)
+ if (!is_uncached_acl(acl))
return acl;
if (!IS_POSIXACL(inode))
return NULL;
+ sentinel = uncached_acl_sentinel(current);
+ p = acl_by_type(inode, type);
+
/*
- * A filesystem can force a ACL callback by just never filling the
- * ACL cache. But normally you'd fill the cache either at inode
- * instantiation time, or on the first ->get_acl call.
+ * If the ACL isn't being read yet, set our sentinel. Otherwise, the
+ * current value of the ACL will not be ACL_NOT_CACHED and so our own
+ * sentinel will not be set; another task will update the cache. We
+ * could wait for that other task to complete its job, but it's easier
+ * to just call ->get_acl to fetch the ACL ourself. (This is going to
+ * be an unlikely race.)
+ */
+ if (cmpxchg(p, ACL_NOT_CACHED, sentinel) != ACL_NOT_CACHED)
+ /* fall through */ ;
+
+ /*
+ * Normally, the ACL returned by ->get_acl will be cached.
+ * A filesystem can prevent that by calling
+ * forget_cached_acl(inode, type) in ->get_acl.
*
* If the filesystem doesn't have a get_acl() function at all, we'll
* just create the negative cache entry.
@@ -119,7 +137,24 @@ struct posix_acl *get_acl(struct inode *inode, int type)
set_cached_acl(inode, type, NULL);
return NULL;
}
- return inode->i_op->get_acl(inode, type);
+ acl = inode->i_op->get_acl(inode, type);
+
+ if (IS_ERR(acl)) {
+ /*
+ * Remove our sentinel so that we don't block future attempts
+ * to cache the ACL.
+ */
+ cmpxchg(p, sentinel, ACL_NOT_CACHED);
+ return acl;
+ }
+
+ /*
+ * Cache the result, but only if our sentinel is still in place.
+ */
+ posix_acl_dup(acl);
+ if (unlikely(cmpxchg(p, sentinel, acl) != sentinel))
+ posix_acl_release(acl);
+ return acl;
}
EXPORT_SYMBOL(get_acl);
diff --git a/fs/reiserfs/xattr_acl.c b/fs/reiserfs/xattr_acl.c
index ec74bbedc8731db5534ff5094cb46a0933c5e3b7..dbed42f755e01ff46518efb35e46a06036b1b52d 100644
--- a/fs/reiserfs/xattr_acl.c
+++ b/fs/reiserfs/xattr_acl.c
@@ -197,10 +197,8 @@ struct posix_acl *reiserfs_get_acl(struct inode *inode, int type)
size = reiserfs_xattr_get(inode, name, NULL, 0);
if (size < 0) {
- if (size == -ENODATA || size == -ENOSYS) {
- set_cached_acl(inode, type, NULL);
+ if (size == -ENODATA || size == -ENOSYS)
return NULL;
- }
return ERR_PTR(size);
}
@@ -220,8 +218,6 @@ struct posix_acl *reiserfs_get_acl(struct inode *inode, int type)
} else {
acl = reiserfs_posix_acl_from_disk(value, retval);
}
- if (!IS_ERR(acl))
- set_cached_acl(inode, type, acl);
kfree(value);
return acl;
diff --git a/fs/xfs/xfs_acl.c b/fs/xfs/xfs_acl.c
index 2d5df1f23bbcbe47cebc087023d04126230cbe6c..b6e527b8eccb6d2917a9ef8a7938da902ed9b7c8 100644
--- a/fs/xfs/xfs_acl.c
+++ b/fs/xfs/xfs_acl.c
@@ -158,22 +158,14 @@ xfs_get_acl(struct inode *inode, int type)
if (error) {
/*
* If the attribute doesn't exist make sure we have a negative
- * cache entry, for any other error assume it is transient and
- * leave the cache entry as ACL_NOT_CACHED.
+ * cache entry, for any other error assume it is transient.
*/
- if (error == -ENOATTR)
- goto out_update_cache;
- acl = ERR_PTR(error);
- goto out;
+ if (error != -ENOATTR)
+ acl = ERR_PTR(error);
+ } else {
+ acl = xfs_acl_from_disk(xfs_acl, len,
+ XFS_ACL_MAX_ENTRIES(ip->i_mount));
}
-
- acl = xfs_acl_from_disk(xfs_acl, len, XFS_ACL_MAX_ENTRIES(ip->i_mount));
- if (IS_ERR(acl))
- goto out;
-
-out_update_cache:
- set_cached_acl(inode, type, acl);
-out:
kmem_free(xfs_acl);
return acl;
}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 14a97194b34ba16ba7906ae8c27b1767f266f317..329ed372d7082f07046f440ac9ae16a86731a1b5 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -577,6 +577,18 @@ static inline void mapping_allow_writable(struct address_space *mapping)
struct posix_acl;
#define ACL_NOT_CACHED ((void *)(-1))
+static inline struct posix_acl *
+uncached_acl_sentinel(struct task_struct *task)
+{
+ return (void *)task + 1;
+}
+
+static inline bool
+is_uncached_acl(struct posix_acl *acl)
+{
+ return (long)acl & 1;
+}
+
#define IOP_FASTPERM 0x0001
#define IOP_LOOKUP 0x0002
#define IOP_NOFOLLOW 0x0004