Convert wbc.range_cyclic to new behavior: when past EOF, abort writeback
of the inode, which instructs writeback_single_inode() to delay it for a
while if necessary.
It removes one inefficient .range_cyclic IO pattern when writeback_index
wraps:
submit [10000-10100], (wrap), submit [0-100]
In which the submitted pages may be consisted of two distant ranges.
It also prevents submitting pointless IO for busy overwriters.
CC: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
fs/ext4/inode.c | 18 ++++--------------
1 file changed, 4 insertions(+), 14 deletions(-)
--- linux.orig/fs/ext4/inode.c 2009-10-06 23:37:48.000000000 +0800
+++ linux/fs/ext4/inode.c 2009-10-06 23:38:35.000000000 +0800
@@ -2805,7 +2805,7 @@ static int ext4_da_writepages(struct add
int pages_written = 0;
long pages_skipped;
unsigned int max_pages;
- int range_cyclic, cycled = 1, io_done = 0;
+ int range_cyclic, io_done = 0;
int needed_blocks, ret = 0;
long desired_nr_to_write, nr_to_writebump = 0;
loff_t range_start = wbc->range_start;
@@ -2840,8 +2840,6 @@ static int ext4_da_writepages(struct add
range_cyclic = wbc->range_cyclic;
if (wbc->range_cyclic) {
index = mapping->writeback_index;
- if (index)
- cycled = 0;
wbc->range_start = index << PAGE_CACHE_SHIFT;
wbc->range_end = LLONG_MAX;
wbc->range_cyclic = 0;
@@ -2889,7 +2887,6 @@ static int ext4_da_writepages(struct add
wbc->no_nrwrite_index_update = 1;
pages_skipped = wbc->pages_skipped;
-retry:
while (!ret && wbc->nr_to_write > 0) {
/*
@@ -2963,20 +2960,13 @@ retry:
wbc->pages_skipped = pages_skipped;
ret = 0;
io_done = 1;
- } else if (wbc->nr_to_write)
+ } else if (wbc->nr_to_write > 0) {
/*
* There is no more writeout needed
- * or we requested for a noblocking writeout
- * and we found the device congested
*/
+ index = 0;
break;
- }
- if (!io_done && !cycled) {
- cycled = 1;
- index = 0;
- wbc->range_start = index << PAGE_CACHE_SHIFT;
- wbc->range_end = mapping->writeback_index - 1;
- goto retry;
+ }
}
if (pages_skipped != wbc->pages_skipped)
ext4_msg(inode->i_sb, KERN_CRIT,
--
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