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SubjectRe: [PATCH 1/1] fs: fix lock imbalance in do_remount_sb()
On Wed, 13 May 2009 21:21:12 +0200
Jiri Slaby <jirislaby@gmail.com> wrote:

> Commit "Push BKL down into do_remount_sb()" pushed un/lock_kernel
> into do_remount_sb but forgets to unlock it on fail paths. Fix
> that.
>

argh, how many times must we teach ourselves this lesson? Perhaps we
can convert this function to have a single `return' to prevent
relapses?

> ---
> fs/super.c | 12 +++++++++---
> 1 files changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/fs/super.c b/fs/super.c
> index e4a0c5b..a64f362 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -548,18 +548,24 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
> if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) {
> if (force)
> mark_files_ro(sb);
> - else if (!fs_may_remount_ro(sb))
> + else if (!fs_may_remount_ro(sb)) {
> + unlock_kernel();
> return -EBUSY;
> + }
> retval = vfs_dq_off(sb, 1);
> - if (retval < 0 && retval != -ENOSYS)
> + if (retval < 0 && retval != -ENOSYS) {
> + unlock_kernel();
> return -EBUSY;

Strange that the code drops the vfs_dq_off() return value on the floor.
`man(2) mount' lists a great pile of possible errnos.

> + }
> }
> remount_rw = !(flags & MS_RDONLY) && (sb->s_flags & MS_RDONLY);
>
> if (sb->s_op->remount_fs) {
> retval = sb->s_op->remount_fs(sb, &flags, data);
> - if (retval)
> + if (retval) {
> + unlock_kernel();
> return retval;
> + }


> }
> sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
> unlock_kernel();



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