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>
This commit is contained in:
Steven Whitehouse 2013-06-14 11:17:15 +01:00
parent 5a00f3cc97
commit 6d4ade986f
4 changed files with 157 additions and 53 deletions

View File

@ -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);

View File

@ -537,11 +537,52 @@ static int gfs2_mmap(struct file *file, struct vm_area_struct *vma)
return 0;
}
/**
* 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 @@ static int gfs2_open(struct inode *inode, struct file *file)
{
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);
if (need_unlock)
gfs2_glock_dq_uninit(&i_gh);
fail_gunlock:
gfs2_glock_dq_uninit(&i_gh);
fail:
file->private_data = NULL;
kfree(fp);
return error;
}

View File

@ -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 = {

View File

@ -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;