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anon-inodes use open coded atomic_inc for the shared inode

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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>
This commit is contained in:
Davide Libenzi 2007-10-16 23:30:19 -07:00 • committed by Linus Torvalds
parent 5e3c3ac9db
commit 96fdc72ddf
1 changed files with 12 additions and 13 deletions
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25
fs/anon_inodes.c
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@ -76,7 +76,6 @@ int anon_inode_getfd(int *pfd, struct inode **pinode, struct file **pfile,
{ {
struct qstr this; struct qstr this;
struct dentry *dentry; struct dentry *dentry;
struct inode *inode;
struct file *file; struct file *file;
int error, fd; int error, fd;
@ -86,15 +85,9 @@ int anon_inode_getfd(int *pfd, struct inode **pinode, struct file **pfile,
if (!file) if (!file)
return -ENFILE; return -ENFILE;
inode = igrab(anon_inode_inode);
if (IS_ERR(inode)) {
error = PTR_ERR(inode);
goto err_put_filp;
}
error = get_unused_fd(); error = get_unused_fd();
if (error < 0) if (error < 0)
goto err_iput; goto err_put_filp;
fd = error; 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); dentry = d_alloc(anon_inode_mnt->mnt_sb->s_root, &this);
if (!dentry) if (!dentry)
goto err_put_unused_fd; 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; dentry->d_op = &anon_inodefs_dentry_operations;
/* Do not publish this dentry inside the global dentry hash table */ /* Do not publish this dentry inside the global dentry hash table */
dentry->d_flags &= ~DCACHE_UNHASHED; 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.mnt = mntget(anon_inode_mnt);
file->f_path.dentry = dentry; 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_pos = 0;
file->f_flags = O_RDWR; 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); fd_install(fd, file);
*pfd = fd; *pfd = fd;
*pinode = inode; *pinode = anon_inode_inode;
*pfile = file; *pfile = file;
return 0; return 0;
err_put_unused_fd: err_put_unused_fd:
put_unused_fd(fd); put_unused_fd(fd);
err_iput:
iput(inode);
err_put_filp: err_put_filp:
put_filp(file); put_filp(file);
return error; return error;