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Message-ID: <20130625133021.GB14581@quack.suse.cz>
Date: Tue, 25 Jun 2013 15:30:21 +0200
From: Jan Kara <jack@...e.cz>
To: Theodore Ts'o <tytso@....edu>
Cc: Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: use ext4_da_writepages() for all modes
On Thu 06-06-13 14:01:16, Ted Tso wrote:
> Rename ext4_da_writepages() to ext4_writepages() and use it for all
> modes. We still need to iterate over all the pages in the case of
> data=journalling, but in the case of nodelalloc/data=ordered (which is
> what file systems mounted using ext3 backwards compatibility will use)
> this will allow us to use a much more efficient I/O submission path.
>
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>
Funny I was thinking about doing the same a few days ago :). Anyway, the
patch looks good. You can add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
> ---
> fs/ext4/inode.c | 41 +++++++++++++++++++++++++++++++----------
> include/trace/events/ext4.h | 4 ++--
> 2 files changed, 33 insertions(+), 12 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 442c5d2..0db830d 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1799,7 +1799,7 @@ out:
> * lock so we have to do some magic.
> *
> * This function can get called via...
> - * - ext4_da_writepages after taking page lock (have journal handle)
> + * - ext4_writepages after taking page lock (have journal handle)
> * - journal_submit_inode_data_buffers (no journal handle)
> * - shrink_page_list via the kswapd/direct reclaim (no journal handle)
> * - grab_page_cache when doing write_begin (have journal handle)
> @@ -2217,7 +2217,7 @@ static int mpage_map_and_submit_extent(handle_t *handle,
>
> /*
> * Calculate the total number of credits to reserve for one writepages
> - * iteration. This is called from ext4_da_writepages(). We map an extent of
> + * iteration. This is called from ext4_writepages(). We map an extent of
> * upto MAX_WRITEPAGES_EXTENT_LEN blocks and then we go on and finish mapping
> * the last partial page. So in total we can map MAX_WRITEPAGES_EXTENT_LEN +
> * bpp - 1 blocks in bpp different extents.
> @@ -2349,8 +2349,17 @@ out:
> return err;
> }
>
> -static int ext4_da_writepages(struct address_space *mapping,
> - struct writeback_control *wbc)
> +static int __writepage(struct page *page, struct writeback_control *wbc,
> + void *data)
> +{
> + struct address_space *mapping = data;
> + int ret = ext4_writepage(page, wbc);
> + mapping_set_error(mapping, ret);
> + return ret;
> +}
> +
> +static int ext4_writepages(struct address_space *mapping,
> + struct writeback_control *wbc)
> {
> pgoff_t writeback_index = 0;
> long nr_to_write = wbc->nr_to_write;
> @@ -2364,7 +2373,7 @@ static int ext4_da_writepages(struct address_space *mapping,
> bool done;
> struct blk_plug plug;
>
> - trace_ext4_da_writepages(inode, wbc);
> + trace_ext4_writepages(inode, wbc);
>
> /*
> * No pages to write? This is mainly a kludge to avoid starting
> @@ -2374,13 +2383,23 @@ static int ext4_da_writepages(struct address_space *mapping,
> if (!mapping->nrpages || !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
> return 0;
>
> + if (ext4_should_journal_data(inode)) {
> + struct blk_plug plug;
> + int ret;
> +
> + blk_start_plug(&plug);
> + ret = write_cache_pages(mapping, wbc, __writepage, mapping);
> + blk_finish_plug(&plug);
> + return ret;
> + }
> +
> /*
> * If the filesystem has aborted, it is read-only, so return
> * right away instead of dumping stack traces later on that
> * will obscure the real source of the problem. We test
> * EXT4_MF_FS_ABORTED instead of sb->s_flag's MS_RDONLY because
> * the latter could be true if the filesystem is mounted
> - * read-only, and in that case, ext4_da_writepages should
> + * read-only, and in that case, ext4_writepages should
> * *never* be called, so if that ever happens, we would want
> * the stack trace.
> */
> @@ -2520,8 +2539,8 @@ retry:
> mapping->writeback_index = mpd.first_page;
>
> out_writepages:
> - trace_ext4_da_writepages_result(inode, wbc, ret,
> - nr_to_write - wbc->nr_to_write);
> + trace_ext4_writepages_result(inode, wbc, ret,
> + nr_to_write - wbc->nr_to_write);
> return ret;
> }
>
> @@ -2769,7 +2788,7 @@ int ext4_alloc_da_blocks(struct inode *inode)
> * laptop_mode, not even desirable). However, to do otherwise
> * would require replicating code paths in:
> *
> - * ext4_da_writepages() ->
> + * ext4_writepages() ->
> * write_cache_pages() ---> (via passed in callback function)
> * __mpage_da_writepage() -->
> * mpage_add_bh_to_extent()
> @@ -3213,6 +3232,7 @@ static const struct address_space_operations ext4_aops = {
> .readpage = ext4_readpage,
> .readpages = ext4_readpages,
> .writepage = ext4_writepage,
> + .writepages = ext4_writepages,
> .write_begin = ext4_write_begin,
> .write_end = ext4_write_end,
> .bmap = ext4_bmap,
> @@ -3228,6 +3248,7 @@ static const struct address_space_operations ext4_journalled_aops = {
> .readpage = ext4_readpage,
> .readpages = ext4_readpages,
> .writepage = ext4_writepage,
> + .writepages = ext4_writepages,
> .write_begin = ext4_write_begin,
> .write_end = ext4_journalled_write_end,
> .set_page_dirty = ext4_journalled_set_page_dirty,
> @@ -3243,7 +3264,7 @@ static const struct address_space_operations ext4_da_aops = {
> .readpage = ext4_readpage,
> .readpages = ext4_readpages,
> .writepage = ext4_writepage,
> - .writepages = ext4_da_writepages,
> + .writepages = ext4_writepages,
> .write_begin = ext4_da_write_begin,
> .write_end = ext4_da_write_end,
> .bmap = ext4_bmap,
> diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
> index 832a412..72f523e 100644
> --- a/include/trace/events/ext4.h
> +++ b/include/trace/events/ext4.h
> @@ -281,7 +281,7 @@ DEFINE_EVENT(ext4__write_end, ext4_da_write_end,
> TP_ARGS(inode, pos, len, copied)
> );
>
> -TRACE_EVENT(ext4_da_writepages,
> +TRACE_EVENT(ext4_writepages,
> TP_PROTO(struct inode *inode, struct writeback_control *wbc),
>
> TP_ARGS(inode, wbc),
> @@ -379,7 +379,7 @@ TRACE_EVENT(ext4_da_write_pages_extent,
> __entry->flags)
> );
>
> -TRACE_EVENT(ext4_da_writepages_result,
> +TRACE_EVENT(ext4_writepages_result,
> TP_PROTO(struct inode *inode, struct writeback_control *wbc,
> int ret, int pages_written),
>
> --
> 1.7.12.rc0.22.gcdd159b
>
> --
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--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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