Commit 96fdc72d authored by Davide Libenzi's avatar Davide Libenzi Committed by Linus Torvalds

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 <>: were checking
for an IS_ERR() return from igrab(), but it actually returns NULL on error.
Signed-off-by: default avatarDavide Libenzi <>
Cc: Yan Zheng <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 5e3c3ac9
......@@ -76,7 +76,6 @@ int anon_inode_getfd(int *pfd, struct inode **pinode, struct file **pfile,
struct qstr this;
struct dentry *dentry;
struct inode *inode;
struct file *file;
int error, fd;
......@@ -86,15 +85,9 @@ int anon_inode_getfd(int *pfd, struct inode **pinode, struct file **pfile,
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 @@ int anon_inode_getfd(int *pfd, struct inode **pinode, struct file **pfile,
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().
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/* Do not publish this dentry inside the global dentry hash table */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 @@ int anon_inode_getfd(int *pfd, struct inode **pinode, struct file **pfile,
fd_install(fd, file);
*pfd = fd;
*pinode = inode;
*pinode = anon_inode_inode;
*pfile = file;
return 0;
return error;
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