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SubjectRe: [PATCH 01/17] writeback: introduce wbc.tagged_sync for the WB_SYNC_NONE sync stage
On Fri 06-05-11 11:08:22, Wu Fengguang wrote:
> sync(2) is performed in two stages: the WB_SYNC_NONE sync and the
> WB_SYNC_ALL sync. Tag the first stage with wbc.tagged_sync and do
> livelock prevention for it, too.
>
> Note that writeback_inodes_sb() is called by not only sync(), they are
> treated the same because the other callers also need livelock prevention.
>
> Impact: It changes the order in which pages/inodes are synced to disk.
> Now in the WB_SYNC_NONE stage, it won't proceed to write the next inode
> until finished with the current inode.
You can add:
Acked-by: Jan Kara <jack@suse.cz>

> CC: Jan Kara <jack@suse.cz>
> CC: Dave Chinner <david@fromorbit.com>
> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> ---
> fs/ext4/inode.c | 4 ++--
> fs/fs-writeback.c | 9 +++++----
> include/linux/writeback.h | 1 +
> mm/page-writeback.c | 4 ++--
> 4 files changed, 10 insertions(+), 8 deletions(-)
>
> --- linux-next.orig/fs/fs-writeback.c 2011-05-05 23:29:51.000000000 +0800
> +++ linux-next/fs/fs-writeback.c 2011-05-05 23:30:22.000000000 +0800
> @@ -36,6 +36,7 @@ struct wb_writeback_work {
> long nr_pages;
> struct super_block *sb;
> enum writeback_sync_modes sync_mode;
> + unsigned int tagged_sync:1;
> unsigned int for_kupdate:1;
> unsigned int range_cyclic:1;
> unsigned int for_background:1;
> @@ -650,6 +651,7 @@ static long wb_writeback(struct bdi_writ
> {
> struct writeback_control wbc = {
> .sync_mode = work->sync_mode,
> + .tagged_sync = work->tagged_sync,
> .older_than_this = NULL,
> .for_kupdate = work->for_kupdate,
> .for_background = work->for_background,
> @@ -657,7 +659,7 @@ static long wb_writeback(struct bdi_writ
> };
> unsigned long oldest_jif;
> long wrote = 0;
> - long write_chunk;
> + long write_chunk = MAX_WRITEBACK_PAGES;
> struct inode *inode;
>
> if (wbc.for_kupdate) {
> @@ -683,9 +685,7 @@ static long wb_writeback(struct bdi_writ
> * (quickly) tag currently dirty pages
> * (maybe slowly) sync all tagged pages
> */
> - if (wbc.sync_mode == WB_SYNC_NONE)
> - write_chunk = MAX_WRITEBACK_PAGES;
> - else
> + if (wbc.sync_mode == WB_SYNC_ALL || wbc.tagged_sync)
> write_chunk = LONG_MAX;
>
> wbc.wb_start = jiffies; /* livelock avoidance */
> @@ -1193,6 +1193,7 @@ void writeback_inodes_sb_nr(struct super
> struct wb_writeback_work work = {
> .sb = sb,
> .sync_mode = WB_SYNC_NONE,
> + .tagged_sync = 1,
> .done = &done,
> .nr_pages = nr,
> };
> --- linux-next.orig/include/linux/writeback.h 2011-05-05 23:29:51.000000000 +0800
> +++ linux-next/include/linux/writeback.h 2011-05-05 23:30:22.000000000 +0800
> @@ -47,6 +47,7 @@ struct writeback_control {
> unsigned encountered_congestion:1; /* An output: a queue is full */
> unsigned for_kupdate:1; /* A kupdate writeback */
> unsigned for_background:1; /* A background writeback */
> + unsigned tagged_sync:1; /* do livelock prevention for sync */
> unsigned for_reclaim:1; /* Invoked from the page allocator */
> unsigned range_cyclic:1; /* range_start is cyclic */
> unsigned more_io:1; /* more io to be dispatched */
> --- linux-next.orig/mm/page-writeback.c 2011-05-05 23:29:51.000000000 +0800
> +++ linux-next/mm/page-writeback.c 2011-05-05 23:30:22.000000000 +0800
> @@ -892,12 +892,12 @@ int write_cache_pages(struct address_spa
> range_whole = 1;
> cycled = 1; /* ignore range_cyclic tests */
> }
> - if (wbc->sync_mode == WB_SYNC_ALL)
> + if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_sync)
> tag = PAGECACHE_TAG_TOWRITE;
> else
> tag = PAGECACHE_TAG_DIRTY;
> retry:
> - if (wbc->sync_mode == WB_SYNC_ALL)
> + if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_sync)
> tag_pages_for_writeback(mapping, index, end);
> done_index = index;
> while (!done && (index <= end)) {
> --- linux-next.orig/fs/ext4/inode.c 2011-05-05 23:29:51.000000000 +0800
> +++ linux-next/fs/ext4/inode.c 2011-05-05 23:30:22.000000000 +0800
> @@ -2741,7 +2741,7 @@ static int write_cache_pages_da(struct a
> index = wbc->range_start >> PAGE_CACHE_SHIFT;
> end = wbc->range_end >> PAGE_CACHE_SHIFT;
>
> - if (wbc->sync_mode == WB_SYNC_ALL)
> + if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_sync)
> tag = PAGECACHE_TAG_TOWRITE;
> else
> tag = PAGECACHE_TAG_DIRTY;
> @@ -2975,7 +2975,7 @@ static int ext4_da_writepages(struct add
> }
>
> retry:
> - if (wbc->sync_mode == WB_SYNC_ALL)
> + if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_sync)
> tag_pages_for_writeback(mapping, index, end);
>
> while (!ret && wbc->nr_to_write > 0) {
>
>
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR


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