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SubjectRe: splice: move balance_dirty_pages_ratelimited() outside of splice actor
On Mon, 11 Jun 2007 21:59:15 GMT
Linux Kernel Mailing List <linux-kernel@vger.kernel.org> wrote:

> Gitweb: http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=20d698db67059a63d217030dfd02872cb5f88dfb
> Commit: 20d698db67059a63d217030dfd02872cb5f88dfb
> Parent: 17374ff1aa9ce2a0597416a16729474b538af443
> Author: Jens Axboe <jens.axboe@oracle.com>
> AuthorDate: Tue Jun 5 11:05:11 2007 +0200
> Committer: Jens Axboe <jens.axboe@oracle.com>
> CommitDate: Fri Jun 8 08:33:59 2007 +0200
>
> splice: move balance_dirty_pages_ratelimited() outside of splice actor
>
> I've seen inode related deadlocks, so move this call outside of the
> actor itself, which may hold the inode lock.
>

eh? If the pipe_to_file() caller holds inode_lock, our problems are large.

I doubt if that's true, so what problem is this patch really fixing??

> ---
> fs/splice.c | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/fs/splice.c b/fs/splice.c
> index b78a7f0..6349d31 100644
> --- a/fs/splice.c
> +++ b/fs/splice.c
> @@ -652,7 +652,6 @@ find_page:
> * accessed, we are now done!
> */
> mark_page_accessed(page);
> - balance_dirty_pages_ratelimited(mapping);
> out:
> page_cache_release(page);
> unlock_page(page);
> @@ -823,6 +822,7 @@ generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
> if (err)
> ret = err;
> }
> + balance_dirty_pages_ratelimited(mapping);
> }
>
> return ret;
> @@ -876,6 +876,7 @@ generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
> if (err)
> ret = err;
> }
> + balance_dirty_pages_ratelimited(mapping);
> }
>

balance_dirty_pages_ratelimited() is supposed to be called
once-per-dirtied-page. This caller can dirty an arbitrarily large amount
of memory and hence should use balance_dirty_pages_ratelimited_nr().

As things stand, a large splice() could potentially cause the dirty limits
to be exceeded.

btw, can we please arrange to get patches reviewed prior to them being
merged?

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