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Commit 96fdc72d authored by Davide Libenzi's avatar Davide Libenzi Committed by Linus Torvalds
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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: default avatarDavide Libenzi <davidel@xmailserver.org>
Cc: Yan Zheng <yanzheng@21cn.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5e3c3ac9

fs/anon_inodes.c

+12 −13
Original line number Diff line number Diff line
@@ -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().

	 */

	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	/* Do not publish this dentry inside the global dentry hash table */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 @@ 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;



err_put_unused_fd:

	put_unused_fd(fd);

err_iput:

	iput(inode);

err_put_filp:

	put_filp(file);

	return error;