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writeback: avoid extra sync work at enqueue time 

This removes writeback_control.wb_start and does more straightforward
sync livelock prevention by setting .older_than_this to prevent extra
inodes from being enqueued in the first place.

Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
This commit is contained in:
Wu Fengguang 2011-04-23 11:26:07 -06:00
parent e8dfc30582
commit e185dda89d
2 changed files with 3 additions and 16 deletions
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16
fs/fs-writeback.c
View File

@ -544,15 +544,6 @@ static int writeback_sb_inodes(struct super_block *sb, struct bdi_writeback *wb,
continue;
}
/*
* Was this inode dirtied after sync_sb_inodes was called?
* This keeps sync from extra jobs and livelock.
*/
if (inode_dirtied_after(inode, wbc->wb_start)) {
spin_unlock(&inode->i_lock);
return 1;
}
__iget(inode);
pages_skipped = wbc->pages_skipped;
@ -585,9 +576,6 @@ static void __writeback_inodes_wb(struct bdi_writeback *wb,
{
int ret = 0;
if (!wbc->wb_start)
wbc->wb_start = jiffies; /* livelock avoidance */
while (!list_empty(&wb->b_io)) {
struct inode *inode = wb_inode(wb->b_io.prev);
struct super_block *sb = inode->i_sb;
@ -686,7 +674,9 @@ static long wb_writeback(struct bdi_writeback *wb,
if (wbc.sync_mode == WB_SYNC_ALL || wbc.tagged_writepages)
write_chunk = LONG_MAX;
wbc.wb_start = jiffies; /* livelock avoidance */
oldest_jif = jiffies;
wbc.older_than_this = &oldest_jif;
spin_lock(&wb->list_lock);
for (;;) {
/*

3
include/linux/writeback.h
View File

@ -26,9 +26,6 @@ struct writeback_control {
enum writeback_sync_modes sync_mode;
unsigned long *older_than_this; /* If !NULL, only write back inodes
older than this */
unsigned long wb_start; /* Time writeback_inodes_wb was
called. This is needed to avoid
extra jobs and livelock */
long nr_to_write; /* Write this many pages, and decrement
this for each page written */
long pages_skipped; /* Pages which were not written */