Messages in this thread | | | Date | Thu, 16 Apr 2009 10:36:26 -0400 | From | Christoph Hellwig <> | Subject | Re: [PATCH -tip] remove the BKL: Replace BKL in mount/umount syscalls with a mutex |
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On Thu, Apr 16, 2009 at 04:27:58PM +0200, Alessio Igor Bogani wrote: > Replace ths BKL in sys_mount()/sys_umount() syscalls with a regular mutex.
Could you try to explain what these actuall try to protect?
> unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); > @@ -1073,9 +1075,9 @@ static int do_umount(struct vfsmount *mnt, int flags) > */ > > if (flags & MNT_FORCE && sb->s_op->umount_begin) { > - lock_kernel(); > + mutex_lock(&mount_lock); > sb->s_op->umount_begin(sb); > - unlock_kernel(); > + mutex_unlock(&mount_lock);
This is a very easy case, just move the lock into ->umount_begin. And then ping the maintainers of the 5 instances actually making use of it - I suspect none of them actually require it.
> @@ -1094,9 +1096,9 @@ static int do_umount(struct vfsmount *mnt, int flags) > */ > down_write(&sb->s_umount); > if (!(sb->s_flags & MS_RDONLY)) { > - lock_kernel(); > + mutex_lock(&mount_lock); > retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); > - unlock_kernel(); > + mutex_unlock(&mount_lock);
I suspect moving lock_kernel down into ->remount_fs is the much better option. Will require some audit of do_remount_sb, though.
> - lock_kernel(); > + mutex_lock(&mount_lock); > retval = do_mount((char *)dev_page, dir_page, (char *)type_page, > flags, (void *)data_page); > - unlock_kernel(); > + mutex_unlock(&mount_lock);
Again, much better to push it down and probably eliminate it completely for all sane filesystems.
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