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writeback: fix WB_SYNC_NONE writeback from umount

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When umount calls sync_filesystem(), we first do a WB_SYNC_NONE
writeback to kick off writeback of pending dirty inodes, then follow
that up with a WB_SYNC_ALL to wait for it. Since umount already holds
the sb s_umount mutex, WB_SYNC_NONE ends up doing nothing and all
writeback happens as WB_SYNC_ALL. This can greatly slow down umount,
since WB_SYNC_ALL writeback is a data integrity operation and thus
a bigger hammer than simple WB_SYNC_NONE. For barrier aware file systems
it's a lot slower.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe
2010-05-17 12:55:07 +02:00
parent 69b62d01ec
commit e913fc825d
5 changed files with 51 additions and 15 deletions
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4
mm/page-writeback.c
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@@ -597,7 +597,7 @@ static void balance_dirty_pages(struct address_space *mapping,
(!laptop_mode && ((global_page_state(NR_FILE_DIRTY)
+ global_page_state(NR_UNSTABLE_NFS))
> background_thresh)))
bdi_start_writeback(bdi, NULL, 0);
bdi_start_writeback(bdi, NULL, 0, 0);
}
void set_page_dirty_balance(struct page *page, int page_mkwrite)
@@ -705,7 +705,7 @@ void laptop_mode_timer_fn(unsigned long data)
*/
if (bdi_has_dirty_io(&q->backing_dev_info))
bdi_start_writeback(&q->backing_dev_info, NULL, nr_pages);
bdi_start_writeback(&q->backing_dev_info, NULL, 0, nr_pages);
}
/*