From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Subject: Re: [PATCH 05/10] fs: return if direct write will trigger writeback Date: Thu, 25 May 2017 10:32:32 +0200 Message-ID: <20170525083232.GF28950@quack2.suse.cz> References: <20170524164150.9492-1-rgoldwyn@suse.de> <20170524164150.9492-6-rgoldwyn@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170524164150.9492-6-rgoldwyn@suse.de> Sender: linux-block-owner@vger.kernel.org To: Goldwyn Rodrigues Cc: linux-fsdevel@vger.kernel.org, jack@suse.com, hch@infradead.org, linux-block@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, axboe@kernel.dk, linux-api@vger.kernel.org, adam.manzanares@wdc.com, viro@zeniv.linux.org.uk, Goldwyn Rodrigues List-Id: linux-api@vger.kernel.org On Wed 24-05-17 11:41:45, Goldwyn Rodrigues wrote: > From: Goldwyn Rodrigues > > Find out if the write will trigger a wait due to writeback. If yes, > return -EAGAIN. > > Return -EINVAL for buffered AIO: there are multiple causes of > delay such as page locks, dirty throttling logic, page loading > from disk etc. which cannot be taken care of. > > Signed-off-by: Goldwyn Rodrigues > Reviewed-by: Christoph Hellwig Looks good. You can add: Reviewed-by: Jan Kara Honza > --- > mm/filemap.c | 17 ++++++++++++++--- > 1 file changed, 14 insertions(+), 3 deletions(-) > > diff --git a/mm/filemap.c b/mm/filemap.c > index 097213275461..bc146efa6815 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -2675,6 +2675,9 @@ inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from) > > pos = iocb->ki_pos; > > + if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT)) > + return -EINVAL; > + > if (limit != RLIM_INFINITY) { > if (iocb->ki_pos >= limit) { > send_sig(SIGXFSZ, current, 0); > @@ -2743,9 +2746,17 @@ generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from) > write_len = iov_iter_count(from); > end = (pos + write_len - 1) >> PAGE_SHIFT; > > - written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1); > - if (written) > - goto out; > + if (iocb->ki_flags & IOCB_NOWAIT) { > + /* If there are pages to writeback, return */ > + if (filemap_range_has_page(inode->i_mapping, pos, > + pos + iov_iter_count(from))) > + return -EAGAIN; > + } else { > + written = filemap_write_and_wait_range(mapping, pos, > + pos + write_len - 1); > + if (written) > + goto out; > + } > > /* > * After a write we want buffered reads to be sure to go to disk to get > -- > 2.12.0 > -- Jan Kara SUSE Labs, CR