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authorDave Chinner <dchinner@redhat.com>2010-06-09 10:37:18 +1000
committerLinus Torvalds <torvalds@linux-foundation.org>2010-06-08 18:12:44 -0700
commit0b5649278e39a068aaf91399941bab1b4a4a3cc2 (patch)
tree3fd2c782385137f5b135c07149de772e207fdaf8 /mm
parent8d7458daea2a6809d32418bf489b949d23de99ea (diff)
downloadkernel-0b5649278e39a068aaf91399941bab1b4a4a3cc2.tar.gz
writeback: pay attention to wbc->nr_to_write in write_cache_pages
If a filesystem writes more than one page in ->writepage, write_cache_pages fails to notice this and continues to attempt writeback when wbc->nr_to_write has gone negative - this trace was captured from XFS: wbc_writeback_start: towrt=1024 wbc_writepage: towrt=1024 wbc_writepage: towrt=0 wbc_writepage: towrt=-1 wbc_writepage: towrt=-5 wbc_writepage: towrt=-21 wbc_writepage: towrt=-85 This has adverse effects on filesystem writeback behaviour. write_cache_pages() needs to terminate after a certain number of pages are written, not after a certain number of calls to ->writepage are made. This is a regression introduced by 17bc6c30cf6bfffd816bdc53682dd46fc34a2cf4 ("vfs: Add no_nrwrite_index_update writeback control flag"), but cannot be reverted directly due to subsequent bug fixes that have gone in on top of it. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/page-writeback.c15
1 files changed, 5 insertions, 10 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 5fa63bdf52e4..b3dbb8040ed5 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -835,7 +835,6 @@ int write_cache_pages(struct address_space *mapping,
pgoff_t done_index;
int cycled;
int range_whole = 0;
- long nr_to_write = wbc->nr_to_write;
pagevec_init(&pvec, 0);
if (wbc->range_cyclic) {
@@ -935,11 +934,10 @@ continue_unlock:
done = 1;
break;
}
- }
+ }
- if (nr_to_write > 0) {
- nr_to_write--;
- if (nr_to_write == 0 &&
+ if (wbc->nr_to_write > 0) {
+ if (--wbc->nr_to_write == 0 &&
wbc->sync_mode == WB_SYNC_NONE) {
/*
* We stop writing back only if we are
@@ -970,11 +968,8 @@ continue_unlock:
end = writeback_index - 1;
goto retry;
}
- if (!wbc->no_nrwrite_index_update) {
- if (wbc->range_cyclic || (range_whole && nr_to_write > 0))
- mapping->writeback_index = done_index;
- wbc->nr_to_write = nr_to_write;
- }
+ if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
+ mapping->writeback_index = done_index;
return ret;
}