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>
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1 changed files with 12 additions and 13 deletions
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@ -76,7 +76,6 @@ int anon_inode_getfd(int *pfd, struct inode **pinode, struct file **pfile,
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{
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struct qstr this;
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struct dentry *dentry;
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struct inode *inode;
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struct file *file;
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int error, fd;
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@ -86,15 +85,9 @@ int anon_inode_getfd(int *pfd, struct inode **pinode, struct file **pfile,
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if (!file)
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return -ENFILE;
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inode = igrab(anon_inode_inode);
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if (IS_ERR(inode)) {
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error = PTR_ERR(inode);
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goto err_put_filp;
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}
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error = get_unused_fd();
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if (error < 0)
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goto err_iput;
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goto err_put_filp;
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fd = error;
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/*
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@ -108,14 +101,22 @@ int anon_inode_getfd(int *pfd, struct inode **pinode, struct file **pfile,
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dentry = d_alloc(anon_inode_mnt->mnt_sb->s_root, &this);
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if (!dentry)
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goto err_put_unused_fd;
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/*
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* We know the anon_inode inode count is always greater than zero,
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* so we can avoid doing an igrab() and we can use an open-coded
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* atomic_inc().
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*/
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atomic_inc(&anon_inode_inode->i_count);
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dentry->d_op = &anon_inodefs_dentry_operations;
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/* Do not publish this dentry inside the global dentry hash table */
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dentry->d_flags &= ~DCACHE_UNHASHED;
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d_instantiate(dentry, inode);
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d_instantiate(dentry, anon_inode_inode);
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file->f_path.mnt = mntget(anon_inode_mnt);
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file->f_path.dentry = dentry;
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file->f_mapping = inode->i_mapping;
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file->f_mapping = anon_inode_inode->i_mapping;
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file->f_pos = 0;
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file->f_flags = O_RDWR;
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@ -127,14 +128,12 @@ int anon_inode_getfd(int *pfd, struct inode **pinode, struct file **pfile,
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fd_install(fd, file);
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*pfd = fd;
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*pinode = inode;
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*pinode = anon_inode_inode;
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*pfile = file;
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return 0;
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err_put_unused_fd:
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put_unused_fd(fd);
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err_iput:
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iput(inode);
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err_put_filp:
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put_filp(file);
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return error;
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