linux-kernel - [PATCH 05/25] vfs: add filesystem flags for atomic

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Date:	Wed,  7 Mar 2012 22:22:22 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	viro@...IV.linux.org.uk
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	hch@...radead.org, Trond.Myklebust@...app.com, sfrench@...ba.org,
	sage@...dream.net, ericvh@...il.com, mszeredi@...e.cz
Subject: [PATCH 05/25] vfs: add filesystem flags for atomic_open

From: Miklos Szeredi <mszeredi@...e.cz>

Allow filesystem to select which cases it wants to perform atomic_open.

Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
---
 fs/namei.c         |   16 +++++++++++++++-
 include/linux/fs.h |    2 ++
 2 files changed, 17 insertions(+), 1 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 835dcf1..8dfbe45 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2227,6 +2227,20 @@ look_up:
 	return NULL;
 }
 
+static bool is_atomic_lookup_open(struct inode *dir, struct nameidata *nd)
+{
+	int fs_flags;
+
+	if (!(nd->flags & LOOKUP_OPEN) || !dir->i_op->atomic_open)
+		return false;
+
+	fs_flags = dir->i_sb->s_type->fs_flags;
+	if (nd->flags & LOOKUP_CREATE)
+		return !(fs_flags & FS_NO_LOOKUP_CREATE);
+	else
+		return !(fs_flags & FS_NO_LOOKUP_OPEN);
+}
+
 /*
  * Lookup and possibly open (and create) the last component
  *
@@ -2253,7 +2267,7 @@ static struct file *lookup_open(struct nameidata *nd, struct path *path,
 	if (!need_lookup && dentry->d_inode)
 		goto out_no_open;
 
-	if ((nd->flags & LOOKUP_OPEN) && dir_inode->i_op->atomic_open) {
+	if (is_atomic_lookup_open(dir_inode, nd)) {
 		struct file *filp;
 
 		filp = atomic_open(nd, dentry, op, want_write, &create_error);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3a47ecd..6615355 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -181,6 +181,8 @@ struct inodes_stat_t {
 #define FS_RENAME_DOES_D_MOVE	32768	/* FS will handle d_move()
 					 * during rename() internally.
 					 */
+#define FS_NO_LOOKUP_OPEN	0x10000	/* fs can't do atomic lookup+open */
+#define FS_NO_LOOKUP_CREATE	0x20000 /* fs can't do lookup+create+open */
 
 /*
  * These are the fs-independent mount-flags: up to 32 flags are supported
-- 
1.7.7

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