On Tue, Feb 23, 2010 at 03:03:28AM +0900, OGAWA Hirofumi wrote:
> Hi,
>
> Please review this. (This originally was for #untested branch, so this is
> not minimal change perfectly.)
>
>
>
> Those might be assuming that the nd->path.mnt refcnt is keeped by
> filp after nameidata_to_filp().
>
> It's wrong if nameidata_to_filp() returned the error. (nd->path and
> filp are invalid)
>
> Instead to use deep knowledge of nameidata_to_filp() internal, this
> thinks the nd->path is invalid after nameidata_to_filp(). So, this
> just take refcnt for mnt_want/drop_write().
You might take a look at the patch I just posted:
Subject: [RFC PATCH] VFS: Simplify truncate logic in do_filp_open()
If that patch is correct, it will considerably simplify the second
part of your patch.
-VAL
>
> Signed-off-by: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
> ---
>
> fs/namei.c | 35 +++++++++++++++++++++++------------
> 1 file changed, 23 insertions(+), 12 deletions(-)
>
> diff -puN fs/namei.c~nameidata_to_filp-mount-writer-fix fs/namei.c
> --- linux-2.6/fs/namei.c~nameidata_to_filp-mount-writer-fix 2010-02-22 23:22:26.000000000 +0900
> +++ linux-2.6-hirofumi/fs/namei.c 2010-02-22 23:59:34.000000000 +0900
> @@ -1617,6 +1617,7 @@ struct file *do_filp_open(int dfd, const
> struct path path;
> struct dentry *dir;
> int count = 0;
> + struct vfsmount *uninitialized_var(mnt_writer);
> int will_truncate;
> int flag = open_to_namei_flags(open_flag);
> int force_reval = 0;
> @@ -1733,16 +1734,20 @@ do_last:
> * a permanent write count is taken through
> * the 'struct file' in nameidata_to_filp().
> */
> - error = mnt_want_write(nd.path.mnt);
> + mnt_writer = nd.path.mnt;
> + error = mnt_want_write(mnt_writer);
> if (error)
> goto exit_mutex_unlock;
> error = __open_namei_create(&nd, &path, flag, mode);
> if (error) {
> - mnt_drop_write(nd.path.mnt);
> + mnt_drop_write(mnt_writer);
> goto exit;
> }
> + mntget(mnt_writer);
> + /* nd->path is invalid after this */
> filp = nameidata_to_filp(&nd);
> - mnt_drop_write(nd.path.mnt);
> + mnt_drop_write(mnt_writer);
> + mntput(mnt_writer);
> if (nd.root.mnt)
> path_put(&nd.root);
> if (!IS_ERR(filp)) {
> @@ -1794,16 +1799,20 @@ ok:
> */
> will_truncate = open_will_truncate(flag, nd.path.dentry->d_inode);
> if (will_truncate) {
> - error = mnt_want_write(nd.path.mnt);
> + mnt_writer = nd.path.mnt;
> + error = mnt_want_write(mnt_writer);
> if (error)
> goto exit;
> }
> error = may_open(&nd.path, acc_mode, flag);
> if (error) {
> if (will_truncate)
> - mnt_drop_write(nd.path.mnt);
> + mnt_drop_write(mnt_writer);
> goto exit;
> }
> + if (will_truncate)
> + mntget(mnt_writer);
> + /* nd->path is invalid after this */
> filp = nameidata_to_filp(&nd);
> if (!IS_ERR(filp)) {
> error = ima_file_check(filp, acc_mode);
> @@ -1814,10 +1823,10 @@ ok:
> }
> if (!IS_ERR(filp)) {
> if (acc_mode & MAY_WRITE)
> - vfs_dq_init(nd.path.dentry->d_inode);
> + vfs_dq_init(filp->f_path.dentry->d_inode);
>
> if (will_truncate) {
> - error = handle_truncate(&nd.path);
> + error = handle_truncate(&filp->f_path);
> if (error) {
> fput(filp);
> filp = ERR_PTR(error);
> @@ -1825,12 +1834,14 @@ ok:
> }
> }
> /*
> - * It is now safe to drop the mnt write
> - * because the filp has had a write taken
> - * on its behalf.
> + * It is now safe to drop the mnt write because the filp has
> + * had a write taken on its behalf. (NOTE: since O_TRUNC can
> + * be used with O_RDONLY, this needs to cover truncate path)
> */
> - if (will_truncate)
> - mnt_drop_write(nd.path.mnt);
> + if (will_truncate) {
> + mnt_drop_write(mnt_writer);
> + mntput(mnt_writer);
> + }
> if (nd.root.mnt)
> path_put(&nd.root);
> return filp;
> _
>
> --
> OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
> --
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