On Sun 14-12-14 21:26:56, Omar Sandoval wrote:
> The generic write code locks i_mutex for a direct_IO. Swap-over-NFS
> doesn't grab the mutex because nfs_direct_IO doesn't expect i_mutex to
> be held, but most direct_IO implementations do.
I think you are speaking about direct IO writes only, aren't you? For DIO
reads we don't hold i_mutex AFAICS. And also for DIO writes we don't
necessarily hold i_mutex - see for example XFS which doesn't take i_mutex
for direct IO writes. It uses it's internal rwlock for this (see
xfs_file_dio_aio_write()). So I think this is just wrong.
Honza
> Signed-off-by: Omar Sandoval <osandov@xxxxxxxxxxx>
> ---
> mm/page_io.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/mm/page_io.c b/mm/page_io.c
> index 955db8b..1630ac0 100644
> --- a/mm/page_io.c
> +++ b/mm/page_io.c
> @@ -263,6 +263,7 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc,
> if (sis->flags & SWP_FILE) {
> struct kiocb kiocb;
> struct file *swap_file = sis->swap_file;
> + struct inode *inode = file_inode(swap_file);
> struct address_space *mapping = swap_file->f_mapping;
> struct bio_vec bv = {
> .bv_page = page,
> @@ -283,9 +284,11 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc,
>
> set_page_writeback(page);
> unlock_page(page);
> + mutex_lock(&inode->i_mutex);
> ret = mapping->a_ops->direct_IO(ITER_BVEC | WRITE,
> &kiocb, &from,
> kiocb.ki_pos);
> + mutex_unlock(&inode->i_mutex);
> if (ret == PAGE_SIZE) {
> count_vm_event(PSWPOUT);
> ret = 0;
> --
> 2.1.3
>
> --
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--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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