On Mon 14-11-11 19:59:12, Wu Fengguang wrote:
> On Mon, Nov 14, 2011 at 07:10:28PM +0800, Jan Kara wrote:
> >
> > Hello,
> >
> > these two patches aim at making task waiting in balance_dirty_pages()
> > killable. This is desirable because otherwise if filesystem stops accepting
> > writes (e.g. if device has been removed or other serious error condidion) we
> > have a task stuck in D state forever.
>
> Agreed totally. I myself has run into such conditions and get very
> annoyed not being able to kill the hard throttled tasks -- they just
> stuck there for ever if the error condition does not change.
>
> > I'm not sure who should merge these two patches... Al, Fengguang?
>
> I'd like to do it -- otherwise there will obviously be merge conflicts.
Good.
> Actually I also queued a patch to do this (attached). Your patches do
> better on TASK_KILLABLE and the use of signal_pending() in write
> routines, while mine goes further to add the break to various
> filesystems. How about combining them together?
>
> Subject: writeback: quit throttling when fatal signal pending
> Date: Wed Sep 08 17:40:22 CST 2010
>
> This allows quick response to Ctrl-C etc. for impatient users.
>
> It's necessary to abort the generic_perform_write() and other filesystem
> write loops too, to avoid large write + SIGKILL combination exceeding
> the dirty limit and possibly strange OOM.
>
> It mainly helps the rare bdi/global dirty exceeded cases.
> In the normal case of not exceeded, it will quit the loop anyway.
>
> if (fatal_signal_pending(current) &&
> nr_reclaimable + nr_writeback <= dirty_thresh)
> break;
>
> Reviewed-by: Neil Brown <neilb@xxxxxxx>
> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
> cc: Chris Mason <chris.mason@xxxxxxxxxx>
> cc: Anton Altaparmakov <aia21@xxxxxxxxxx>
> Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
> ---
> fs/btrfs/file.c | 4 ++++
> fs/btrfs/ioctl.c | 4 ++++
> fs/btrfs/relocation.c | 4 ++++
> fs/buffer.c | 4 ++++
> fs/ntfs/attrib.c | 2 ++
> fs/ntfs/file.c | 6 ++++++
> mm/filemap.c | 3 ++-
> mm/page-writeback.c | 2 ++
> 8 files changed, 28 insertions(+), 1 deletion(-)
>
> --- linux-next.orig/mm/page-writeback.c 2011-11-13 20:37:11.000000000 +0800
> +++ linux-next/mm/page-writeback.c 2011-11-13 20:37:57.000000000 +0800
> @@ -1185,6 +1185,8 @@ pause:
> */
> if (task_ratelimit)
> break;
> + if (fatal_signal_pending(current))
> + break;
> }
>
> if (!dirty_exceeded && bdi->dirty_exceeded)
> --- linux-next.orig/mm/filemap.c 2011-11-13 20:03:23.000000000 +0800
> +++ linux-next/mm/filemap.c 2011-11-13 20:37:17.000000000 +0800
> @@ -2463,7 +2463,8 @@ again:
> written += copied;
>
> balance_dirty_pages_ratelimited(mapping);
> -
> + if (fatal_signal_pending(current))
> + break;
> } while (iov_iter_count(i));
>
> return written ? written : status;
Above two hunks are already part of my patches (effectively). The hunks
below look good but I guess they should be split to per-filesystem patches
and sent to filesystem maintainers for merging. The changes are independent
so there's no reason to do them in one big patch or skip fs maintainers...
Honza
> --- linux-next.orig/fs/btrfs/file.c 2011-11-13 20:37:11.000000000 +0800
> +++ linux-next/fs/btrfs/file.c 2011-11-13 20:37:17.000000000 +0800
> @@ -1274,6 +1274,10 @@ static noinline ssize_t __btrfs_buffered
> dirty_pages);
> if (dirty_pages < (root->leafsize >> PAGE_CACHE_SHIFT) + 1)
> btrfs_btree_balance_dirty(root, 1);
> + if (fatal_signal_pending(current)) {
> + ret = -EINTR;
> + break;
> + }
> btrfs_throttle(root);
>
> pos += copied;
> --- linux-next.orig/fs/btrfs/ioctl.c 2011-11-13 20:03:23.000000000 +0800
> +++ linux-next/fs/btrfs/ioctl.c 2011-11-13 20:37:17.000000000 +0800
> @@ -1115,6 +1115,10 @@ int btrfs_defrag_file(struct inode *inod
>
> defrag_count += ret;
> balance_dirty_pages_ratelimited_nr(inode->i_mapping, ret);
> + if (fatal_signal_pending(current)) {
> + ret = -EINTR;
> + goto out_ra;
> + }
>
> if (newer_than) {
> if (newer_off == (u64)-1)
> --- linux-next.orig/fs/btrfs/relocation.c 2011-11-13 20:03:23.000000000 +0800
> +++ linux-next/fs/btrfs/relocation.c 2011-11-13 20:37:17.000000000 +0800
> @@ -3009,6 +3009,10 @@ static int relocate_file_extent_cluster(
>
> index++;
> balance_dirty_pages_ratelimited(inode->i_mapping);
> + if (fatal_signal_pending(current)) {
> + ret = -EINTR;
> + break;
> + }
> btrfs_throttle(BTRFS_I(inode)->root);
> }
> WARN_ON(nr != cluster->nr);
> --- linux-next.orig/fs/buffer.c 2011-11-13 20:03:23.000000000 +0800
> +++ linux-next/fs/buffer.c 2011-11-13 20:37:17.000000000 +0800
> @@ -2255,6 +2255,10 @@ static int cont_expand_zero(struct file
> err = 0;
>
> balance_dirty_pages_ratelimited(mapping);
> + if (fatal_signal_pending(current)) {
> + err = -EINTR;
> + goto out;
> + }
> }
>
> /* page covers the boundary, find the boundary offset */
> --- linux-next.orig/fs/ntfs/attrib.c 2011-11-13 20:03:23.000000000 +0800
> +++ linux-next/fs/ntfs/attrib.c 2011-11-13 20:37:17.000000000 +0800
> @@ -2588,6 +2588,8 @@ int ntfs_attr_set(ntfs_inode *ni, const
> unlock_page(page);
> page_cache_release(page);
> balance_dirty_pages_ratelimited(mapping);
> + if (fatal_signal_pending(current))
> + return -EINTR;
> cond_resched();
> }
> /* If there is a last partial page, need to do it the slow way. */
> --- linux-next.orig/fs/ntfs/file.c 2011-11-13 20:03:23.000000000 +0800
> +++ linux-next/fs/ntfs/file.c 2011-11-13 20:37:17.000000000 +0800
> @@ -278,6 +278,10 @@ do_non_resident_extend:
> * files.
> */
> balance_dirty_pages_ratelimited(mapping);
> + if (fatal_signal_pending(current)) {
> + err = -EINTR;
> + goto init_err_out;
> + }
> cond_resched();
> } while (++index < end_index);
> read_lock_irqsave(&ni->size_lock, flags);
> @@ -2054,6 +2058,8 @@ static ssize_t ntfs_file_buffered_write(
> if (unlikely(status))
> break;
> balance_dirty_pages_ratelimited(mapping);
> + if (fatal_signal_pending(current))
> + break;
> cond_resched();
> } while (count);
> err_out:
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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