Re: [PATCH] memory mapped files not updating timestamps

[Eric Dumazet <dada1@cosmosbay.com>]

Peter Staubach a écrit :
> --- linux-2.6.16.i686/mm/msync.c.org
> +++ linux-2.6.16.i686/mm/msync.c
> @@ -206,12 +206,16 @@ asmlinkage long sys_msync(unsigned long 
>  		file = vma->vm_file;
>  		start = vma->vm_end;
>  		if ((flags & MS_ASYNC) && file && nr_pages_dirtied) {
> +			struct address_space *mapping = file->f_mapping;
> +
>  			get_file(file);
>  			up_read(&current->mm->mmap_sem);
> -			balance_dirty_pages_ratelimited_nr(file->f_mapping,
> +			balance_dirty_pages_ratelimited_nr(mapping,
>  							nr_pages_dirtied);
>  			fput(file);

<here>, another thread can perform an munmap(), and the file can be totally 
dismantled.

>  			down_read(&current->mm->mmap_sem);

So referencing 'mapping' is *buggy* here.
I believe that you have to move 'fput(file);' *after* the folloging two lines.

> +			if (test_and_clear_bit(AS_MCTIME, &mapping->flags))
> +				inode_update_time(mapping->host);
>  			vma = find_vma(current->mm, start);
>  		} else if ((flags & MS_SYNC) && file &&
>  				(vma->vm_flags & VM_SHARED)) {


Eric