reiserfs: eliminate per-super xattr lock

With the switch to using inode->i_mutex locking during lookups/creation
in the xattr root, the per-super xattr lock is no longer needed.

This patch removes it.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 35 insertions, 35 deletions

diff --git a/fs/reiserfs/xattr.c b/fs/reiserfs/xattr.c
index 57920a4df7a4..62c98829c545 100644
--- a/fs/reiserfs/xattr.c
+++ b/fs/reiserfs/xattr.c
@@ -27,6 +27,12 @@
  * these are special cases for filesystem ACLs, they are interpreted by the
  * kernel, in addition, they are negatively and positively cached and attached
  * 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.
  */
 
 #include <linux/reiserfs_fs.h>
@@ -392,16 +398,17 @@ reiserfs_delete_xattrs_filler(void *buf, const char *name, int namelen,
 /* This is called w/ inode->i_mutex downed */
 int reiserfs_delete_xattrs(struct inode *inode)
 {
-        struct dentry *dir, *root;
         int err = 0;
+        struct dentry *dir, *root;
+        struct reiserfs_transaction_handle th;
+        int blocks = JOURNAL_PER_BALANCE_CNT * 2 + 2 +
+                     4 * REISERFS_QUOTA_TRANS_BLOCKS(inode->i_sb);
 
         /* Skip out, an xattr has no xattrs associated with it */
         if (IS_PRIVATE(inode) || get_inode_sd_version(inode) == STAT_DATA_V1)
                 return 0;
 
-        reiserfs_read_lock_xattrs(inode->i_sb);
         dir = open_xa_dir(inode, XATTR_REPLACE);
-        reiserfs_read_unlock_xattrs(inode->i_sb);
         if (IS_ERR(dir)) {
                 err = PTR_ERR(dir);
                 goto out;
@@ -416,18 +423,26 @@ int reiserfs_delete_xattrs(struct inode *inode)
         if (err)
                 goto out_dir;
 
-        /* Leftovers besides . and .. -- that's not good. */
-        if (dir->d_inode->i_nlink <= 2) {
-                root = open_xa_root(inode->i_sb, XATTR_REPLACE);
-                reiserfs_write_lock_xattrs(inode->i_sb);
+        /* We start a transaction here to avoid a ABBA situation
+         * between the xattr root's i_mutex and the journal lock.
+         * Inode creation will inherit an ACL, which requires a
+         * lookup. The lookup locks the xattr root i_mutex with a
+         * transaction open.  Inode deletion takes teh xattr root
+         * i_mutex to delete the directory and then starts a
+         * transaction inside it. Boom. This doesn't incur much
+         * additional overhead since the reiserfs_rmdir transaction
+         * will just nest inside the outer transaction. */
+        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);
-                reiserfs_write_unlock_xattrs(inode->i_sb);
                 dput(root);
-        } else {
-                reiserfs_warning(inode->i_sb, "jdm-20006",
-                                 "Couldn't remove all entries in directory");
+
+                err = jerror ?: err;
         }
 
 out_dir:
@@ -437,6 +452,9 @@ out:
         if (!err)
                 REISERFS_I(inode)->i_flags =
                     REISERFS_I(inode)->i_flags & ~i_has_xattr_dir;
+        else
+                reiserfs_warning(inode->i_sb, "jdm-20004",
+                                 "Couldn't remove all xattrs (%d)\n", err);
         return err;
 }
 
@@ -485,9 +503,7 @@ int reiserfs_chown_xattrs(struct inode *inode, struct iattr *attrs)
         if (IS_PRIVATE(inode) || get_inode_sd_version(inode) == STAT_DATA_V1)
                 return 0;
 
-        reiserfs_read_lock_xattrs(inode->i_sb);
         dir = open_xa_dir(inode, XATTR_REPLACE);
-        reiserfs_read_unlock_xattrs(inode->i_sb);
         if (IS_ERR(dir)) {
                 if (PTR_ERR(dir) != -ENODATA)
                         err = PTR_ERR(dir);
@@ -731,6 +747,11 @@ reiserfs_xattr_get(const struct inode *inode, const char *name, void *buffer,
                 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);
+
         isize = i_size_read(dentry->d_inode);
         REISERFS_I(inode)->i_flags |= i_has_xattr_dir;
 
@@ -798,6 +819,7 @@ reiserfs_xattr_get(const struct inode *inode, const char *name, void *buffer,
         }
 
 out_dput:
+        mutex_unlock(&dentry->d_inode->i_mutex);
         dput(dentry);
 
 out:
@@ -834,7 +856,6 @@ int reiserfs_xattr_del(struct inode *inode, const char *name)
 static struct reiserfs_xattr_handler *find_xattr_handler_prefix(const char *);
 /*
  * Inode operation getxattr()
- * Preliminary locking: we down dentry->d_inode->i_mutex
  */
 ssize_t
 reiserfs_getxattr(struct dentry * dentry, const char *name, void *buffer,
@@ -848,9 +869,7 @@ reiserfs_getxattr(struct dentry * dentry, const char *name, void *buffer,
                 return -EOPNOTSUPP;
 
         reiserfs_read_lock_xattr_i(dentry->d_inode);
-        reiserfs_read_lock_xattrs(dentry->d_sb);
         err = xah->get(dentry->d_inode, name, buffer, size);
-        reiserfs_read_unlock_xattrs(dentry->d_sb);
         reiserfs_read_unlock_xattr_i(dentry->d_inode);
         return err;
 }
@@ -866,23 +885,13 @@ reiserfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 {
         struct reiserfs_xattr_handler *xah = find_xattr_handler_prefix(name);
         int err;
-        int lock;
 
         if (!xah || !reiserfs_xattrs(dentry->d_sb) ||
             get_inode_sd_version(dentry->d_inode) == STAT_DATA_V1)
                 return -EOPNOTSUPP;
 
         reiserfs_write_lock_xattr_i(dentry->d_inode);
-        lock = !has_xattr_dir(dentry->d_inode);
-        if (lock)
-                reiserfs_write_lock_xattrs(dentry->d_sb);
-        else
-                reiserfs_read_lock_xattrs(dentry->d_sb);
         err = xah->set(dentry->d_inode, name, value, size, flags);
-        if (lock)
-                reiserfs_write_unlock_xattrs(dentry->d_sb);
-        else
-                reiserfs_read_unlock_xattrs(dentry->d_sb);
         reiserfs_write_unlock_xattr_i(dentry->d_inode);
         return err;
 }
@@ -902,8 +911,6 @@ int reiserfs_removexattr(struct dentry *dentry, const char *name)
                 return -EOPNOTSUPP;
 
         reiserfs_write_lock_xattr_i(dentry->d_inode);
-        reiserfs_read_lock_xattrs(dentry->d_sb);
-
         /* Deletion pre-operation */
         if (xah->del) {
                 err = xah->del(dentry->d_inode, name);
@@ -917,7 +924,6 @@ int reiserfs_removexattr(struct dentry *dentry, const char *name)
         mark_inode_dirty(dentry->d_inode);
 
       out:
-        reiserfs_read_unlock_xattrs(dentry->d_sb);
         reiserfs_write_unlock_xattr_i(dentry->d_inode);
         return err;
 }
@@ -966,8 +972,6 @@ reiserfs_listxattr_filler(void *buf, const char *name, int namelen,
 
 /*
  * Inode operation listxattr()
- *
- * Preliminary locking: we down dentry->d_inode->i_mutex
  */
 ssize_t reiserfs_listxattr(struct dentry * dentry, char *buffer, size_t size)
 {
@@ -983,9 +987,7 @@ ssize_t reiserfs_listxattr(struct dentry * dentry, char *buffer, size_t size)
                 return -EOPNOTSUPP;
 
         reiserfs_read_lock_xattr_i(dentry->d_inode);
-        reiserfs_read_lock_xattrs(dentry->d_sb);
         dir = open_xa_dir(dentry->d_inode, XATTR_REPLACE);
-        reiserfs_read_unlock_xattrs(dentry->d_sb);
         if (IS_ERR(dir)) {
                 err = PTR_ERR(dir);
                 if (err == -ENODATA)
@@ -1114,11 +1116,9 @@ static int reiserfs_check_acl(struct inode *inode, int mask)
         int error = -EAGAIN; /* do regular unix permission checks by default */
 
         reiserfs_read_lock_xattr_i(inode);
-        reiserfs_read_lock_xattrs(inode->i_sb);
 
         acl = reiserfs_get_acl(inode, ACL_TYPE_ACCESS);
 
-        reiserfs_read_unlock_xattrs(inode->i_sb);
         reiserfs_read_unlock_xattr_i(inode);
 
         if (acl) {