[patch 21/35 xattr-rework] reiserfs: make per-inode xattr locking more fine grained

From: Jeff Mahoney
Date: Mon Mar 30 2009 - 14:27:24 EST

The per-inode locking can be made more fine-grained to surround just the
interaction with the filesystem itself. This really only applies to protecting
reads during a write, since concurrent writes are barred with inode->i_mutex
at the vfs level.

Signed-off-by: Jeff Mahoney <jeffm@xxxxxxxx>

--
fs/reiserfs/xattr.c | 114 +++++++++++++++++++----------------------
fs/reiserfs/xattr_acl.c | 7 --
include/linux/reiserfs_fs_i.h | 2
include/linux/reiserfs_xattr.h | 22 -------
4 files changed, 55 insertions(+), 90 deletions(-)

--- a/fs/reiserfs/xattr_acl.c
+++ b/fs/reiserfs/xattr_acl.c
@@ -418,9 +418,7 @@ int reiserfs_cache_default_acl(struct in
int ret = 0;
if (reiserfs_posixacl(inode->i_sb) && !IS_PRIVATE(inode)) {
struct posix_acl *acl;
- reiserfs_read_lock_xattr_i(inode);
acl = reiserfs_get_acl(inode, ACL_TYPE_DEFAULT);
- reiserfs_read_unlock_xattr_i(inode);
ret = (acl && !IS_ERR(acl));
if (ret)
posix_acl_release(acl);
@@ -452,11 +450,8 @@ int reiserfs_acl_chmod(struct inode *ino
if (!clone)
return -ENOMEM;
error = posix_acl_chmod_masq(clone, inode->i_mode);
- if (!error) {
- reiserfs_write_lock_xattr_i(inode);
+ if (!error)
error = reiserfs_set_acl(inode, ACL_TYPE_ACCESS, clone);
- reiserfs_write_unlock_xattr_i(inode);
- }
posix_acl_release(clone);
return error;
}
--- a/fs/reiserfs/xattr.c
+++ b/fs/reiserfs/xattr.c
@@ -29,10 +29,8 @@
* to the inode so that unnecessary lookups are avoided.
*
* Locking works like so:
- * The xattr root (/.reiserfs_priv/xattrs) is protected by its i_mutex.
- * The xattr dir (/.reiserfs_priv/xattrs/<oid>.<gen>) is protected by
- * inode->xattr_sem.
- * The xattrs themselves are likewise protected by the xattr_sem.
+ * Directory components (xattr root, xattr dir) are protectd by their i_mutex.
+ * The xattrs themselves are protected by the xattr_sem.
*/

#include <linux/reiserfs_fs.h>
@@ -55,6 +53,8 @@
#define PRIVROOT_NAME ".reiserfs_priv"
#define XAROOT_NAME "xattrs"

+static struct reiserfs_xattr_handler *find_xattr_handler_prefix(const char *);
+
/* Helpers for inode ops. We do this so that we don't have all the VFS
* overhead and also for proper i_mutex annotation.
* dir->i_mutex must be held for all of them. */
@@ -339,12 +339,14 @@ int xattr_readdir(struct inode *inode, f
return res;
}

+/* expects xadir->d_inode->i_mutex to be locked */
static int
__reiserfs_xattr_del(struct dentry *xadir, const char *name, int namelen)
{
struct dentry *dentry;
struct inode *dir = xadir->d_inode;
int err = 0;
+ struct reiserfs_xattr_handler *xah;

dentry = lookup_one_len(name, xadir, namelen);
if (IS_ERR(dentry)) {
@@ -372,6 +374,14 @@ __reiserfs_xattr_del(struct dentry *xadi
return -EIO;
}

+ /* Deletion pre-operation */
+ xah = find_xattr_handler_prefix(name);
+ if (xah && xah->del) {
+ err = xah->del(dentry->d_inode, name);
+ if (err)
+ goto out;
+ }
+
err = xattr_unlink(dir, dentry);

out_file:
@@ -398,7 +408,7 @@ reiserfs_delete_xattrs_filler(void *buf,
/* This is called w/ inode->i_mutex downed */
int reiserfs_delete_xattrs(struct inode *inode)
{
- int err = 0;
+ int err = -ENODATA;
struct dentry *dir, *root;
struct reiserfs_transaction_handle th;
int blocks = JOURNAL_PER_BALANCE_CNT * 2 + 2 +
@@ -414,14 +424,19 @@ int reiserfs_delete_xattrs(struct inode
goto out;
} else if (!dir->d_inode) {
dput(dir);
- return 0;
+ goto out;
}

mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_XATTR);
err = xattr_readdir(dir->d_inode, reiserfs_delete_xattrs_filler, dir);
mutex_unlock(&dir->d_inode->i_mutex);
- if (err)
- goto out_dir;
+ if (err) {
+ dput(dir);
+ goto out;
+ }
+
+ root = dget(dir->d_parent);
+ dput(dir);

/* We start a transaction here to avoid a ABBA situation
* between the xattr root's i_mutex and the journal lock.
@@ -435,19 +450,14 @@ int reiserfs_delete_xattrs(struct inode
err = journal_begin(&th, inode->i_sb, blocks);
if (!err) {
int jerror;
- root = dget(dir->d_parent);
mutex_lock_nested(&root->d_inode->i_mutex, I_MUTEX_XATTR);
err = xattr_rmdir(root->d_inode, dir);
jerror = journal_end(&th, inode->i_sb, blocks);
mutex_unlock(&root->d_inode->i_mutex);
- dput(root);
-
err = jerror ?: err;
}

-out_dir:
- dput(dir);
-
+ dput(root);
out:
if (!err)
REISERFS_I(inode)->i_flags =
@@ -484,7 +494,7 @@ reiserfs_chown_xattrs_filler(void *buf,

if (!S_ISDIR(xafile->d_inode->i_mode)) {
mutex_lock_nested(&xafile->d_inode->i_mutex, I_MUTEX_CHILD);
- err = notify_change(xafile, attrs);
+ err = reiserfs_setattr(xafile, attrs);
mutex_unlock(&xafile->d_inode->i_mutex);
}
dput(xafile);
@@ -520,13 +530,16 @@ int reiserfs_chown_xattrs(struct inode *
err = xattr_readdir(dir->d_inode, reiserfs_chown_xattrs_filler, &buf);

if (!err)
- err = notify_change(dir, attrs);
+ err = reiserfs_setattr(dir, attrs);
mutex_unlock(&dir->d_inode->i_mutex);

attrs->ia_valid = ia_valid;
out_dir:
dput(dir);
out:
+ if (err)
+ reiserfs_warning(inode->i_sb, "jdm-20007",
+ "Couldn't chown all xattrs (%d)\n", err);
return err;
}

@@ -635,9 +648,8 @@ reiserfs_xattr_set(struct inode *inode,
if (get_inode_sd_version(inode) == STAT_DATA_V1)
return -EOPNOTSUPP;

- /* Empty xattrs are ok, they're just empty files, no hash */
- if (buffer && buffer_size)
- xahash = xattr_hash(buffer, buffer_size);
+ if (!buffer)
+ return reiserfs_xattr_del(inode, name);

dentry = get_xa_file_dentry(inode, name, flags);
if (IS_ERR(dentry)) {
@@ -645,13 +657,19 @@ reiserfs_xattr_set(struct inode *inode,
goto out;
}

+ down_write(&REISERFS_I(inode)->i_xattr_sem);
+
+ xahash = xattr_hash(buffer, buffer_size);
REISERFS_I(inode)->i_flags |= i_has_xattr_dir;

/* Resize it so we're ok to write there */
newattrs.ia_size = buffer_size;
+ newattrs.ia_ctime = current_fs_time(inode->i_sb);
newattrs.ia_valid = ATTR_SIZE | ATTR_CTIME;
mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_XATTR);
- err = notify_change(dentry, &newattrs);
+ down_write(&dentry->d_inode->i_alloc_sem);
+ err = reiserfs_setattr(dentry, &newattrs);
+ up_write(&dentry->d_inode->i_alloc_sem);
mutex_unlock(&dentry->d_inode->i_mutex);
if (err)
goto out_filp;
@@ -712,6 +730,7 @@ reiserfs_xattr_set(struct inode *inode,
}

out_filp:
+ up_write(&REISERFS_I(inode)->i_xattr_sem);
dput(dentry);

out:
@@ -747,10 +766,7 @@ reiserfs_xattr_get(const struct inode *i
goto out;
}

- /* protect against concurrent access. xattrs are backed by
- * regular files, but they're not regular files. The updates
- * must be atomic from the perspective of the user. */
- mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_XATTR);
+ down_read(&REISERFS_I(inode)->i_xattr_sem);

isize = i_size_read(dentry->d_inode);
REISERFS_I(inode)->i_flags |= i_has_xattr_dir;
@@ -758,12 +774,12 @@ reiserfs_xattr_get(const struct inode *i
/* Just return the size needed */
if (buffer == NULL) {
err = isize - sizeof(struct reiserfs_xattr_header);
- goto out_dput;
+ goto out_unlock;
}

if (buffer_size < isize - sizeof(struct reiserfs_xattr_header)) {
err = -ERANGE;
- goto out_dput;
+ goto out_unlock;
}

while (file_pos < isize) {
@@ -778,7 +794,7 @@ reiserfs_xattr_get(const struct inode *i
page = reiserfs_get_page(dentry->d_inode, file_pos);
if (IS_ERR(page)) {
err = PTR_ERR(page);
- goto out_dput;
+ goto out_unlock;
}

lock_page(page);
@@ -797,7 +813,7 @@ reiserfs_xattr_get(const struct inode *i
"associated with %k", name,
INODE_PKEY(inode));
err = -EIO;
- goto out_dput;
+ goto out_unlock;
}
hash = le32_to_cpu(rxh->h_hash);
}
@@ -818,8 +834,8 @@ reiserfs_xattr_get(const struct inode *i
err = -EIO;
}

-out_dput:
- mutex_unlock(&dentry->d_inode->i_mutex);
+out_unlock:
+ up_read(&REISERFS_I(inode)->i_xattr_sem);
dput(dentry);

out:
@@ -852,8 +868,6 @@ int reiserfs_xattr_del(struct inode *ino
}

/* Actual operations that are exported to VFS-land */
-
-static struct reiserfs_xattr_handler *find_xattr_handler_prefix(const char *);
/*
* Inode operation getxattr()
*/
@@ -868,9 +882,7 @@ reiserfs_getxattr(struct dentry * dentry
get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
return -EOPNOTSUPP;

- reiserfs_read_lock_xattr_i(dentry->d_inode);
err = xah->get(dentry->d_inode, name, buffer, size);
- reiserfs_read_unlock_xattr_i(dentry->d_inode);
return err;
}

@@ -890,9 +902,7 @@ reiserfs_setxattr(struct dentry *dentry,
get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
return -EOPNOTSUPP;

- reiserfs_write_lock_xattr_i(dentry->d_inode);
err = xah->set(dentry->d_inode, name, value, size, flags);
- reiserfs_write_unlock_xattr_i(dentry->d_inode);
return err;
}

@@ -910,21 +920,11 @@ int reiserfs_removexattr(struct dentry *
get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
return -EOPNOTSUPP;

- reiserfs_write_lock_xattr_i(dentry->d_inode);
- /* Deletion pre-operation */
- if (xah->del) {
- err = xah->del(dentry->d_inode, name);
- if (err)
- goto out;
- }
-
err = reiserfs_xattr_del(dentry->d_inode, name);

dentry->d_inode->i_ctime = CURRENT_TIME_SEC;
mark_inode_dirty(dentry->d_inode);

- out:
- reiserfs_write_unlock_xattr_i(dentry->d_inode);
return err;
}

@@ -986,7 +986,6 @@ ssize_t reiserfs_listxattr(struct dentry
get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
return -EOPNOTSUPP;

- reiserfs_read_lock_xattr_i(dentry->d_inode);
dir = open_xa_dir(dentry->d_inode, XATTR_REPLACE);
if (IS_ERR(dir)) {
err = PTR_ERR(dir);
@@ -1005,19 +1004,16 @@ ssize_t reiserfs_listxattr(struct dentry
mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_XATTR);
err = xattr_readdir(dir->d_inode, reiserfs_listxattr_filler, &buf);
mutex_unlock(&dir->d_inode->i_mutex);
- if (err)
- goto out_dir;

- if (buf.r_pos > buf.r_size && buffer != NULL)
- err = -ERANGE;
- else
- err = buf.r_pos;
+ if (!err) {
+ if (buf.r_pos > buf.r_size && buffer != NULL)
+ err = -ERANGE;
+ else
+ err = buf.r_pos;
+ }

- out_dir:
dput(dir);
-
- out:
- reiserfs_read_unlock_xattr_i(dentry->d_inode);
+out:
return err;
}

@@ -1115,12 +1111,8 @@ static int reiserfs_check_acl(struct ino
struct posix_acl *acl;
int error = -EAGAIN; /* do regular unix permission checks by default */

- reiserfs_read_lock_xattr_i(inode);
-
acl = reiserfs_get_acl(inode, ACL_TYPE_ACCESS);

- reiserfs_read_unlock_xattr_i(inode);
-
if (acl) {
if (!IS_ERR(acl)) {
error = posix_acl_permission(inode, acl, mask);
--- a/include/linux/reiserfs_fs_i.h
+++ b/include/linux/reiserfs_fs_i.h
@@ -59,7 +59,7 @@ struct reiserfs_inode_info {
struct posix_acl *i_acl_default;
#endif
#ifdef CONFIG_REISERFS_FS_XATTR
- struct rw_semaphore xattr_sem;
+ struct rw_semaphore i_xattr_sem;
#endif
struct inode vfs_inode;
};
--- a/include/linux/reiserfs_xattr.h
+++ b/include/linux/reiserfs_xattr.h
@@ -67,24 +67,6 @@ extern struct reiserfs_xattr_handler use
extern struct reiserfs_xattr_handler trusted_handler;
extern struct reiserfs_xattr_handler security_handler;

-static inline void reiserfs_write_lock_xattr_i(struct inode *inode)
-{
- down_write(&REISERFS_I(inode)->i_xattr_sem);
-}
-static inline void reiserfs_write_unlock_xattr_i(struct inode *inode)
-{
- up_write(&REISERFS_I(inode)->i_xattr_sem);
-}
-static inline void reiserfs_read_lock_xattr_i(struct inode *inode)
-{
- down_read(&REISERFS_I(inode)->i_xattr_sem);
-}
-
-static inline void reiserfs_read_unlock_xattr_i(struct inode *inode)
-{
- up_read(&REISERFS_I(inode)->i_xattr_sem);
-}
-
static inline void reiserfs_init_xattr_rwsem(struct inode *inode)
{
init_rwsem(&REISERFS_I(inode)->i_xattr_sem);
@@ -96,10 +78,6 @@ static inline void reiserfs_init_xattr_r
#define reiserfs_setxattr NULL
#define reiserfs_listxattr NULL
#define reiserfs_removexattr NULL
-#define reiserfs_write_lock_xattrs(sb) do {;} while(0)
-#define reiserfs_write_unlock_xattrs(sb) do {;} while(0)
-#define reiserfs_read_lock_xattrs(sb)
-#define reiserfs_read_unlock_xattrs(sb)

#define reiserfs_permission NULL



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