lkml.org 
[lkml]   [2013]   [Jun]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectGFS2: Add atomic_open support
From
Date

The following patch implements atomic_open for GFS2. This is mostly
straightforward, however there is one corner case which I've had to
deal with, beyond what would normally be expected for a local
filesystem.

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/dcache.c b/fs/dcache.c
index f09b908..5a23073 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1612,6 +1612,10 @@ EXPORT_SYMBOL(d_obtain_alias);
* If a dentry was found and moved, then it is returned. Otherwise NULL
* is returned. This matches the expected return value of ->lookup.
*
+ * Cluster filesystems may call this function with a negative, hashed dentry.
+ * In that case, we know that the inode will be a regular file, and also this
+ * will only occur during atomic_open. So we need to check for the dentry
+ * being already hashed only in the final case.
*/
struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
{
@@ -1636,8 +1640,11 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
security_d_instantiate(dentry, inode);
d_rehash(dentry);
}
- } else
- d_add(dentry, inode);
+ } else {
+ d_instantiate(dentry, inode);
+ if (d_unhashed(dentry))
+ d_rehash(dentry);
+ }
return new;
}
EXPORT_SYMBOL(d_splice_alias);
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
@@ -538,21 +538,30 @@ static int gfs2_mmap(struct file *file, struct vm_area_struct *vma)
}

/**
- * gfs2_open - open a file
- * @inode: the inode to open
- * @file: the struct file for this opening
+ * gfs2_open_common - This is common to open and atomic_open
+ * @inode: The inode being opened
+ * @file: The file being opened
*
- * Returns: errno
+ * 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
*/

-static int gfs2_open(struct inode *inode, struct file *file)
+int gfs2_open_common(struct inode *inode, struct file *file)
{
- struct gfs2_inode *ip = GFS2_I(inode);
- struct gfs2_holder i_gh;
struct gfs2_file *fp;
- int error;
+ int ret;

- fp = kzalloc(sizeof(struct gfs2_file), GFP_KERNEL);
+ 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;

@@ -560,29 +569,43 @@ static int gfs2_open(struct inode *inode, struct file *file)

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
+ */
+
+static int gfs2_open(struct inode *inode, struct file *file)
+{
+ struct gfs2_inode *ip = GFS2_I(inode);
+ struct gfs2_holder i_gh;
+ int error;
+ 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;
+ return error;
+ need_unlock = true;
+ }

- if (!(file->f_flags & O_LARGEFILE) &&
- i_size_read(inode) > MAX_NON_LFS) {
- error = -EOVERFLOW;
- goto fail_gunlock;
- }
+ error = gfs2_open_common(inode, file);

+ if (need_unlock)
gfs2_glock_dq_uninit(&i_gh);
- }
-
- return 0;

-fail_gunlock:
- gfs2_glock_dq_uninit(&i_gh);
-fail:
- file->private_data = NULL;
- kfree(fp);
return error;
}

diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 5fbb8df..065c7fb 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -546,6 +546,7 @@ 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
@@ -555,8 +556,9 @@ 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];
@@ -564,6 +566,7 @@ 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;
@@ -586,9 +589,14 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
error = create_ok(dip, name, mode);
if ((error == -EEXIST) && S_ISREG(mode) && !excl) {
inode = gfs2_lookupi(dir, &dentry->d_name, 0);
+ d = d_splice_alias(inode, dentry);
+ error = 0;
+ if (file && !IS_ERR(d))
+ error = finish_open(file, dentry, gfs2_open_common, opened);
gfs2_glock_dq_uninit(ghs);
- d_instantiate(dentry, inode);
- return PTR_RET(inode);
+ if (IS_ERR(d))
+ return PTR_RET(d);
+ return error;
}
if (error)
goto fail_gunlock;
@@ -686,10 +694,12 @@ 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);
@@ -729,36 +739,54 @@ 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
* @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 || IS_ERR(inode))
+ return d_splice_alias(inode, dentry);
+
+ 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)
+ 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);
}

/**
@@ -1076,7 +1104,7 @@ 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);
}

/**
@@ -1092,7 +1120,7 @@ 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);
}

/**
@@ -1107,7 +1135,38 @@ 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)
+ return 0;
+
+ if (!(flags & O_CREAT))
+ return -ENOENT;
+
+ return gfs2_create_inode(dir, dentry, file, S_IFREG | mode, 0, NULL, 0, excl, opened);
}

/*
@@ -1787,6 +1846,7 @@ 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 = {
diff --git a/fs/gfs2/inode.h b/fs/gfs2/inode.h
index c53c747..ba4d949 100644
--- a/fs/gfs2/inode.h
+++ b/fs/gfs2/inode.h
@@ -109,6 +109,7 @@ extern int gfs2_permission(struct inode *inode, int mask);
extern int gfs2_setattr_simple(struct inode *inode, struct iattr *attr);
extern struct inode *gfs2_lookup_simple(struct inode *dip, const char *name);
extern void gfs2_dinode_out(const struct gfs2_inode *ip, void *buf);
+extern int gfs2_open_common(struct inode *inode, struct file *file);

extern const struct inode_operations gfs2_file_iops;
extern const struct inode_operations gfs2_dir_iops;



\
 
 \ /
  Last update: 2013-06-06 17:21    [W:0.078 / U:1.596 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site