anon-inodes use open coded atomic_inc for the shared inode
Since we know the shared inode count is always >0, we can avoid igrab()
and use an open coded atomic_inc().
This also fixes a bug noticed by Yan Zheng <yanzheng@21cn.com>: were checking
for an IS_ERR() return from igrab(), but it actually returns NULL on error.
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Cc: Yan Zheng <yanzheng@21cn.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
index b4a7588..2332188 100644
--- a/fs/anon_inodes.c
+++ b/fs/anon_inodes.c
@@ -76,7 +76,6 @@
{
struct qstr this;
struct dentry *dentry;
- struct inode *inode;
struct file *file;
int error, fd;
@@ -86,15 +85,9 @@
if (!file)
return -ENFILE;
- inode = igrab(anon_inode_inode);
- if (IS_ERR(inode)) {
- error = PTR_ERR(inode);
- goto err_put_filp;
- }
-
error = get_unused_fd();
if (error < 0)
- goto err_iput;
+ goto err_put_filp;
fd = error;
/*
@@ -108,14 +101,22 @@
dentry = d_alloc(anon_inode_mnt->mnt_sb->s_root, &this);
if (!dentry)
goto err_put_unused_fd;
+
+ /*
+ * We know the anon_inode inode count is always greater than zero,
+ * so we can avoid doing an igrab() and we can use an open-coded
+ * atomic_inc().
+ */
+ atomic_inc(&anon_inode_inode->i_count);
+
dentry->d_op = &anon_inodefs_dentry_operations;
/* Do not publish this dentry inside the global dentry hash table */
dentry->d_flags &= ~DCACHE_UNHASHED;
- d_instantiate(dentry, inode);
+ d_instantiate(dentry, anon_inode_inode);
file->f_path.mnt = mntget(anon_inode_mnt);
file->f_path.dentry = dentry;
- file->f_mapping = inode->i_mapping;
+ file->f_mapping = anon_inode_inode->i_mapping;
file->f_pos = 0;
file->f_flags = O_RDWR;
@@ -127,14 +128,12 @@
fd_install(fd, file);
*pfd = fd;
- *pinode = inode;
+ *pinode = anon_inode_inode;
*pfile = file;
return 0;
err_put_unused_fd:
put_unused_fd(fd);
-err_iput:
- iput(inode);
err_put_filp:
put_filp(file);
return error;