From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Hansen Subject: [RFC][PATCH 19/20] elevate writer count for custom 'struct file' Date: Fri, 16 Jun 2006 16:12:27 -0700 Message-ID: <20060616231227.3DB969AB@localhost.localdomain> References: <20060616231213.D4C5D6AF@localhost.localdomain> Cc: linux-fsdevel@vger.kernel.org, herbert@13thfloor.at, viro@ftp.linux.org.uk, Dave Hansen Return-path: Received: from e5.ny.us.ibm.com ([32.97.182.145]:21180 "EHLO e5.ny.us.ibm.com") by vger.kernel.org with ESMTP id S932106AbWFPXMc (ORCPT ); Fri, 16 Jun 2006 19:12:32 -0400 To: linux-kernel@vger.kernel.org In-Reply-To: <20060616231213.D4C5D6AF@localhost.localdomain> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Some filesystems forego the vfs and may_open() and create their own 'struct file's. Any of these users which set the write flag on the file will cause an extra mnt_drop_write() on __fput(), thus dropping the reference count too low. These users tend to have artifical in-kernel vfsmounts which aren't really exposed to userspace and can't be remounted, but this patch is included for completeness and so that the warnings don't trip over these cases. Signed-off-by: Dave Hansen --- lxc-dave/fs/hugetlbfs/inode.c | 2 ++ lxc-dave/mm/shmem.c | 2 ++ lxc-dave/mm/tiny-shmem.c | 2 ++ lxc-dave/net/socket.c | 3 +++ 4 files changed, 9 insertions(+) diff -puN fs/hugetlbfs/inode.c~fix-__fput-rev2 fs/hugetlbfs/inode.c --- lxc/fs/hugetlbfs/inode.c~fix-__fput-rev2 2006-06-16 15:58:11.000000000 -0700 +++ lxc-dave/fs/hugetlbfs/inode.c 2006-06-16 15:58:11.000000000 -0700 @@ -790,6 +790,8 @@ struct file *hugetlb_zero_setup(size_t s file->f_mapping = inode->i_mapping; file->f_op = &hugetlbfs_file_operations; file->f_mode = FMODE_WRITE | FMODE_READ; + error = mnt_want_write(hugetlbfs_vfsmount); + WARN_ON(error); return file; out_inode: diff -puN mm/shmem.c~fix-__fput-rev2 mm/shmem.c --- lxc/mm/shmem.c~fix-__fput-rev2 2006-06-16 15:58:11.000000000 -0700 +++ lxc-dave/mm/shmem.c 2006-06-16 15:58:11.000000000 -0700 @@ -2324,6 +2324,8 @@ struct file *shmem_file_setup(char *name file->f_mapping = inode->i_mapping; file->f_op = &shmem_file_operations; file->f_mode = FMODE_WRITE | FMODE_READ; + error = mnt_want_write(shm_mnt); + WARN_ON(error); return file; close_file: diff -puN mm/tiny-shmem.c~fix-__fput-rev2 mm/tiny-shmem.c --- lxc/mm/tiny-shmem.c~fix-__fput-rev2 2006-06-16 15:58:11.000000000 -0700 +++ lxc-dave/mm/tiny-shmem.c 2006-06-16 15:58:11.000000000 -0700 @@ -88,6 +88,8 @@ struct file *shmem_file_setup(char *name file->f_mapping = inode->i_mapping; file->f_op = &ramfs_file_operations; file->f_mode = FMODE_WRITE | FMODE_READ; + error = mnt_want_write(shm_mnt); + WARN_ON(error); /* notify everyone as to the change of file size */ error = do_truncate(dentry, size, 0, file); diff -puN net/socket.c~fix-__fput-rev2 net/socket.c --- lxc/net/socket.c~fix-__fput-rev2 2006-06-16 15:58:11.000000000 -0700 +++ lxc-dave/net/socket.c 2006-06-16 15:58:11.000000000 -0700 @@ -395,6 +395,7 @@ static int sock_attach_fd(struct socket { struct qstr this; char name[32]; + int error; this.len = sprintf(name, "[%lu]", SOCK_INODE(sock)->i_ino); this.name = name; @@ -415,6 +416,8 @@ static int sock_attach_fd(struct socket file->f_flags = O_RDWR; file->f_pos = 0; file->private_data = sock; + error = mnt_want_write(sock_mnt); + WARN_ON(error); return 0; } _