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writeback: stop background writeback when below background threshold

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Treat bdi_start_writeback(0) as a special request to do background write,
and stop such work when we are below the background dirty threshold.

Also simplify the (nr_pages <= 0) checks. Since we already pass in
nr_pages=LONG_MAX for WB_SYNC_ALL and background writes, we don't
need to worry about it being decreased to zero.

Reported-by: Richard Kennedy <richard@rsk.demon.co.uk>
CC: Jan Kara <jack@suse.cz>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Wu Fengguang 2009-09-23 20:33:40 +08:00 committed by Jens Axboe
parent 3a2e9a5a2a
commit d3ddec7635
2 changed files with 20 additions and 14 deletions
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28
fs/fs-writeback.c
View File

@ -41,8 +41,9 @@ struct wb_writeback_args {
long nr_pages;
struct super_block *sb;
enum writeback_sync_modes sync_mode;
int for_kupdate;
int range_cyclic;
int for_kupdate:1;
int range_cyclic:1;
int for_background:1;
};
/*
@ -257,6 +258,15 @@ void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
.range_cyclic = 1,
};
/*
* We treat @nr_pages=0 as the special case to do background writeback,
* ie. to sync pages until the background dirty threshold is reached.
*/
if (!nr_pages) {
args.nr_pages = LONG_MAX;
args.for_background = 1;
}
bdi_alloc_queue_work(bdi, &args);
}
@ -720,20 +730,16 @@ static long wb_writeback(struct bdi_writeback *wb,
for (;;) {
/*
* Don't flush anything for non-integrity writeback where
* no nr_pages was given
* Stop writeback when nr_pages has been consumed
*/
if (!args->for_kupdate && args->nr_pages <= 0 &&
args->sync_mode == WB_SYNC_NONE)
if (args->nr_pages <= 0)
break;
/*
* If no specific pages were given and this is just a
* periodic background writeout and we are below the
* background dirty threshold, don't do anything
* For background writeout, stop when we are below the
* background dirty threshold
*/
if (args->for_kupdate && args->nr_pages <= 0 &&
!over_bground_thresh())
if (args->for_background && !over_bground_thresh())
break;
wbc.more_io = 0;

4
mm/page-writeback.c
View File

@ -593,10 +593,10 @@ static void balance_dirty_pages(struct address_space *mapping,
* background_thresh, to keep the amount of dirty memory low.
*/
if ((laptop_mode && pages_written) ||
(!laptop_mode && ((nr_writeback = global_page_state(NR_FILE_DIRTY)
(!laptop_mode && ((global_page_state(NR_FILE_DIRTY)
+ global_page_state(NR_UNSTABLE_NFS))
> background_thresh)))
bdi_start_writeback(bdi, nr_writeback);
bdi_start_writeback(bdi, 0);
}
void set_page_dirty_balance(struct page *page, int page_mkwrite)