From: Miklos Szeredi <miklos@xxxxxxxxxx>
atomic_open() will do an open-by-name or create-and-open
depending on the flags.
If file was created, then the old positive dentry is obviously
stale, so it will be invalidated and a new one will be allocated.
If not created, then check whether it's the same inode (same as in
->d_revalidate()) and if not, invalidate & allocate new dentry.
Changes from Miklos initial patch (by Bernd):
- LOOKUP_ATOMIC_REVALIDATE was added and is set for revalidate
calls into the file system when revalidate by atomic open is
supported - this is to avoid that ->d_revalidate() would skip
revalidate and set DCACHE_ATOMIC_OPEN, although vfs
does not supported it in the given code path (for example
when LOOKUP_RCU is set)).
- Support atomic-open-revalidate in lookup_fast() - allow atomic
open for positive dentries without O_CREAT being set.
Signed-off-by: Miklos Szeredi <miklos@xxxxxxxxxx>
Signed-off-by: Bernd Schubert <bschubert@xxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Dharmendra Singh <dsingh@xxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
---
fs/fuse/dir.c | 5 ++---
fs/namei.c | 17 +++++++++++++----
include/linux/dcache.h | 6 ++++++
include/linux/namei.h | 1 +
4 files changed, 22 insertions(+), 7 deletions(-)
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index c02b63fe91ca..8ccd49d63235 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -380,7 +380,6 @@ int fuse_lookup_name(struct super_block *sb, u64 nodeid, const struct qstr *name
if (name->len > FUSE_NAME_MAX)
goto out;
-
forget = fuse_alloc_forget();
err = -ENOMEM;
if (!forget)
@@ -771,8 +770,8 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry,
}
static int _fuse_atomic_open(struct inode *dir, struct dentry *entry,
- struct file *file, unsigned flags,
- umode_t mode)
+ struct file *file, unsigned flags,
+ umode_t mode)
{
int err;
diff --git a/fs/namei.c b/fs/namei.c
index e4fe0879ae55..5dae1b1afd0e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1643,12 +1643,14 @@ static struct dentry *lookup_fast(struct nameidata *nd)
return ERR_PTR(-ECHILD);
if (status == -ECHILD)
/* we'd been told to redo it in non-rcu mode */
- status = d_revalidate(dentry, nd->flags);
+ status = d_revalidate(dentry,
+ nd->flags | LOOKUP_ATOMIC_REVALIDATE);
} else {
dentry = __d_lookup(parent, &nd->last);
if (unlikely(!dentry))
return NULL;
- status = d_revalidate(dentry, nd->flags);
+ status = d_revalidate(dentry,
+ nd->flags | LOOKUP_ATOMIC_REVALIDATE);
}
if (unlikely(status <= 0)) {
if (!status)
@@ -1656,6 +1658,12 @@ static struct dentry *lookup_fast(struct nameidata *nd)
dput(dentry);
return ERR_PTR(status);
}
+
+ if (unlikely(d_atomic_open(dentry))) {
+ dput(dentry);
+ return NULL;
+ }
+
return dentry;
}
@@ -3421,7 +3429,8 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
if (d_in_lookup(dentry))
break;
- error = d_revalidate(dentry, nd->flags);
+ error = d_revalidate(dentry,
+ nd->flags | LOOKUP_ATOMIC_REVALIDATE);
if (likely(error > 0))
break;
if (error)
@@ -3430,7 +3439,7 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
dput(dentry);
dentry = NULL;
}
- if (dentry->d_inode) {
+ if (dentry->d_inode && !d_atomic_open(dentry)) {
/* Cached positive dentry: will open in f_op->open */
return dentry;
}
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 6b351e009f59..f90eec22691c 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -208,6 +208,7 @@ struct dentry_operations {
#define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */
#define DCACHE_NOKEY_NAME 0x02000000 /* Encrypted name encoded without key */
#define DCACHE_OP_REAL 0x04000000
+#define DCACHE_ATOMIC_OPEN 0x08000000 /* Always use ->atomic_open() to open this file */
#define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */
#define DCACHE_DENTRY_CURSOR 0x20000000
@@ -496,6 +497,11 @@ static inline bool d_is_fallthru(const struct dentry *dentry)
return dentry->d_flags & DCACHE_FALLTHRU;
}
+static inline bool d_atomic_open(const struct dentry *dentry)
+{
+ return dentry->d_flags & DCACHE_ATOMIC_OPEN;
+}
+
extern int sysctl_vfs_cache_pressure;
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 1463cbda4888..7eec6c06b192 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -33,6 +33,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT};
#define LOOKUP_CREATE 0x0200 /* ... in object creation */
#define LOOKUP_EXCL 0x0400 /* ... in exclusive creation */
#define LOOKUP_RENAME_TARGET 0x0800 /* ... in destination of rename() */
+#define LOOKUP_ATOMIC_REVALIDATE 0x1000 /* atomic revalidate possible */
/* internal use only */
#define LOOKUP_PARENT 0x0010
--
2.34.1
