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>
diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index ad0dc38..4ed6a03 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -538,10 +538,51 @@
}
/**
+ * gfs2_open_common - This is common to open and atomic_open
+ * @inode: The inode being opened
+ * @file: The file being opened
+ *
+ * This maybe called under a glock or not depending upon how it has
+ * been called. We must always be called under a glock for regular
+ * files, however. For other file types, it does not matter whether
+ * we hold the glock or not.
+ *
+ * Returns: Error code or 0 for success
+ */
+
+int gfs2_open_common(struct inode *inode, struct file *file)
+{
+ struct gfs2_file *fp;
+ int ret;
+
+ if (S_ISREG(inode->i_mode)) {
+ ret = generic_file_open(inode, file);
+ if (ret)
+ return ret;
+ }
+
+ fp = kzalloc(sizeof(struct gfs2_file), GFP_NOFS);
+ if (!fp)
+ return -ENOMEM;
+
+ mutex_init(&fp->f_fl_mutex);
+
+ gfs2_assert_warn(GFS2_SB(inode), !file->private_data);
+ file->private_data = fp;
+ return 0;
+}
+
+/**
* gfs2_open - open a file
* @inode: the inode to open
* @file: the struct file for this opening
*
+ * After atomic_open, this function is only used for opening files
+ * which are already cached. We must still get the glock for regular
+ * files to ensure that we have the file size uptodate for the large
+ * file check which is in the common code. That is only an issue for
+ * regular files though.
+ *
* Returns: errno
*/
@@ -549,40 +590,22 @@
{
struct gfs2_inode *ip = GFS2_I(inode);
struct gfs2_holder i_gh;
- struct gfs2_file *fp;
int error;
-
- fp = kzalloc(sizeof(struct gfs2_file), GFP_KERNEL);
- if (!fp)
- return -ENOMEM;
-
- mutex_init(&fp->f_fl_mutex);
-
- gfs2_assert_warn(GFS2_SB(inode), !file->private_data);
- file->private_data = fp;
+ bool need_unlock = false;
if (S_ISREG(ip->i_inode.i_mode)) {
error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY,
&i_gh);
if (error)
- goto fail;
-
- if (!(file->f_flags & O_LARGEFILE) &&
- i_size_read(inode) > MAX_NON_LFS) {
- error = -EOVERFLOW;
- goto fail_gunlock;
- }
-
- gfs2_glock_dq_uninit(&i_gh);
+ return error;
+ need_unlock = true;
}
- return 0;
+ error = gfs2_open_common(inode, file);
-fail_gunlock:
- gfs2_glock_dq_uninit(&i_gh);
-fail:
- file->private_data = NULL;
- kfree(fp);
+ if (need_unlock)
+ gfs2_glock_dq_uninit(&i_gh);
+
return error;
}