GFS2: Add atomic_open support

I've restricted atomic_open to only operate on regular files, although
I still don't understand why atomic_open should not be possible also for
directories on GFS2. That can always be added in later though, if it
makes sense.

The ->atomic_open function can be passed negative dentries, which
in most cases means either ENOENT (->lookup) or a call to d_instantiate
(->create). In the GFS2 case though, we need to actually perform the
look up, since we do not know whether there has been a new inode created
on another node. The look up calls d_splice_alias which then tries to
rehash the dentry - so the solution here is to simply check for that
in d_splice_alias. The same issue is likely to affect any other cluster
filesystem implementing ->atomic_open

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "J. Bruce Fields" <bfields fieldses org>
Cc: Jeff Layton <jlayton@redhat.com>

1 files changed, 99 insertions, 26 deletions

diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index ede16ae784e..bbb2715171c 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -535,6 +535,7 @@ static int gfs2_security_init(struct gfs2_inode *dip, struct gfs2_inode *ip,
  * gfs2_create_inode - Create a new inode
  * @dir: The parent directory
  * @dentry: The new dentry
+ * @file: If non-NULL, the file which is being opened
  * @mode: The permissions on the new inode
  * @dev: For device nodes, this is the device number
  * @symname: For symlinks, this is the link destination
@@ -544,8 +545,9 @@ static int gfs2_security_init(struct gfs2_inode *dip, struct gfs2_inode *ip,
  */
 
 static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
+			     struct file *file,
 			     umode_t mode, dev_t dev, const char *symname,
-			     unsigned int size, int excl)
+			     unsigned int size, int excl, int *opened)
 {
 	const struct qstr *name = &dentry->d_name;
 	struct gfs2_holder ghs[2];
@@ -553,6 +555,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
 	struct gfs2_inode *dip = GFS2_I(dir), *ip;
 	struct gfs2_sbd *sdp = GFS2_SB(&dip->i_inode);
 	struct gfs2_glock *io_gl;
+	struct dentry *d;
 	int error;
 	u32 aflags = 0;
 	int arq;
@@ -579,9 +582,20 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
 	inode = gfs2_dir_search(dir, &dentry->d_name, !S_ISREG(mode) || excl);
 	error = PTR_ERR(inode);
 	if (!IS_ERR(inode)) {
+		d = d_splice_alias(inode, dentry);
+		error = 0;
+		if (file && !IS_ERR(d)) {
+			if (d == NULL)
+				d = dentry;
+			if (S_ISREG(inode->i_mode))
+				error = finish_open(file, d, gfs2_open_common, opened);
+			else
+				error = finish_no_open(file, d);
+		}
 		gfs2_glock_dq_uninit(ghs);
-		d_instantiate(dentry, inode);
-		return 0;
+		if (IS_ERR(d))
+			return PTR_RET(d);
+		return error;
 	} else if (error != -ENOENT) {
 		goto fail_gunlock;
 	}
@@ -679,10 +693,12 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
 		goto fail_gunlock3;
 
 	mark_inode_dirty(inode);
+	d_instantiate(dentry, inode);
+	if (file)
+		error = finish_open(file, dentry, gfs2_open_common, opened);
 	gfs2_glock_dq_uninit(ghs);
 	gfs2_glock_dq_uninit(ghs + 1);
-	d_instantiate(dentry, inode);
-	return 0;
+	return error;
 
 fail_gunlock3:
 	gfs2_glock_dq_uninit(ghs + 1);
@@ -722,36 +738,56 @@ fail:
 static int gfs2_create(struct inode *dir, struct dentry *dentry,
 		       umode_t mode, bool excl)
 {
-	return gfs2_create_inode(dir, dentry, S_IFREG | mode, 0, NULL, 0, excl);
+	return gfs2_create_inode(dir, dentry, NULL, S_IFREG | mode, 0, NULL, 0, excl, NULL);
 }
 
 /**
- * gfs2_lookup - Look up a filename in a directory and return its inode
+ * __gfs2_lookup - Look up a filename in a directory and return its inode
  * @dir: The directory inode
  * @dentry: The dentry of the new inode
- * @nd: passed from Linux VFS, ignored by us
+ * @file: File to be opened
+ * @opened: atomic_open flags
  *
- * Called by the VFS layer. Lock dir and call gfs2_lookupi()
  *
  * Returns: errno
  */
 
-static struct dentry *gfs2_lookup(struct inode *dir, struct dentry *dentry,
-				  unsigned int flags)
+static struct dentry *__gfs2_lookup(struct inode *dir, struct dentry *dentry,
+				    struct file *file, int *opened)
 {
-	struct inode *inode = gfs2_lookupi(dir, &dentry->d_name, 0);
-	if (inode && !IS_ERR(inode)) {
-		struct gfs2_glock *gl = GFS2_I(inode)->i_gl;
-		struct gfs2_holder gh;
-		int error;
-		error = gfs2_glock_nq_init(gl, LM_ST_SHARED, LM_FLAG_ANY, &gh);
-		if (error) {
-			iput(inode);
-			return ERR_PTR(error);
-		}
-		gfs2_glock_dq_uninit(&gh);
+	struct inode *inode;
+	struct dentry *d;
+	struct gfs2_holder gh;
+	struct gfs2_glock *gl;
+	int error;
+
+	inode = gfs2_lookupi(dir, &dentry->d_name, 0);
+	if (!inode)
+		return NULL;
+	if (IS_ERR(inode))
+		return ERR_CAST(inode);
+
+	gl = GFS2_I(inode)->i_gl;
+	error = gfs2_glock_nq_init(gl, LM_ST_SHARED, LM_FLAG_ANY, &gh);
+	if (error) {
+		iput(inode);
+		return ERR_PTR(error);
 	}
-	return d_splice_alias(inode, dentry);
+
+	d = d_splice_alias(inode, dentry);
+	if (file && S_ISREG(inode->i_mode))
+		error = finish_open(file, dentry, gfs2_open_common, opened);
+
+	gfs2_glock_dq_uninit(&gh);
+	if (error)
+		return ERR_PTR(error);
+	return d;
+}
+
+static struct dentry *gfs2_lookup(struct inode *dir, struct dentry *dentry,
+				  unsigned flags)
+{
+	return __gfs2_lookup(dir, dentry, NULL, NULL);
 }
 
 /**
@@ -1069,7 +1105,7 @@ static int gfs2_symlink(struct inode *dir, struct dentry *dentry,
 	if (size > sdp->sd_sb.sb_bsize - sizeof(struct gfs2_dinode) - 1)
 		return -ENAMETOOLONG;
 
-	return gfs2_create_inode(dir, dentry, S_IFLNK | S_IRWXUGO, 0, symname, size, 0);
+	return gfs2_create_inode(dir, dentry, NULL, S_IFLNK | S_IRWXUGO, 0, symname, size, 0, NULL);
 }
 
 /**
@@ -1085,7 +1121,7 @@ static int gfs2_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
 {
 	struct gfs2_sbd *sdp = GFS2_SB(dir);
 	unsigned dsize = sdp->sd_sb.sb_bsize - sizeof(struct gfs2_dinode);
-	return gfs2_create_inode(dir, dentry, S_IFDIR | mode, 0, NULL, dsize, 0);
+	return gfs2_create_inode(dir, dentry, NULL, S_IFDIR | mode, 0, NULL, dsize, 0, NULL);
 }
 
 /**
@@ -1100,7 +1136,43 @@ static int gfs2_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
 static int gfs2_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
 		      dev_t dev)
 {
-	return gfs2_create_inode(dir, dentry, mode, dev, NULL, 0, 0);
+	return gfs2_create_inode(dir, dentry, NULL, mode, dev, NULL, 0, 0, NULL);
+}
+
+/**
+ * gfs2_atomic_open - Atomically open a file
+ * @dir: The directory
+ * @dentry: The proposed new entry
+ * @file: The proposed new struct file
+ * @flags: open flags
+ * @mode: File mode
+ * @opened: Flag to say whether the file has been opened or not
+ *
+ * Returns: error code or 0 for success
+ */
+
+static int gfs2_atomic_open(struct inode *dir, struct dentry *dentry,
+                            struct file *file, unsigned flags,
+                            umode_t mode, int *opened)
+{
+	struct dentry *d;
+	bool excl = !!(flags & O_EXCL);
+
+	d = __gfs2_lookup(dir, dentry, file, opened);
+	if (IS_ERR(d))
+		return PTR_ERR(d);
+	if (d == NULL)
+		d = dentry;
+	if (d->d_inode) {
+		if (!(*opened & FILE_OPENED))
+			return finish_no_open(file, d);
+		return 0;
+	}
+
+	if (!(flags & O_CREAT))
+		return -ENOENT;
+
+	return gfs2_create_inode(dir, dentry, file, S_IFREG | mode, 0, NULL, 0, excl, opened);
 }
 
 /*
@@ -1780,6 +1852,7 @@ const struct inode_operations gfs2_dir_iops = {
 	.removexattr = gfs2_removexattr,
 	.fiemap = gfs2_fiemap,
 	.get_acl = gfs2_get_acl,
+	.atomic_open = gfs2_atomic_open,
 };
 
 const struct inode_operations gfs2_symlink_iops = {