The patch titled
mm: write_cache_pages cyclic fix
has been added to the -mm tree. Its filename is
mm-write_cache_pages-cyclic-fix.patch
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------------------------------------------------------
Subject: mm: write_cache_pages cyclic fix
From: Nick Piggin <npiggin@xxxxxxx>
In write_cache_pages, scanned == 1 is supposed to mean that cyclic
writeback has circled through zero, thus we should not circle again.
However it gets set to 1 after the first successful pagevec lookup. This
leads to cases where not enough data gets written.
Counterexample: file with first 10 pages dirty, writeback_index == 5,
nr_to_write == 10. Then the 5 last pages will be found, and scanned will
be set to 1, after writing those out, we will not cycle back to get the
first 5.
Rework this logic, now we'll always cycle unless we started off from index
0. When cycling, only write out as far as 1 page before the start page
from the first cycle (so we don't write parts of the file twice).
Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
Cc: Chris Mason <chris.mason@xxxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: jim owens <jowens@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page-writeback.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)
diff -puN mm/page-writeback.c~mm-write_cache_pages-cyclic-fix mm/page-writeback.c
--- a/mm/page-writeback.c~mm-write_cache_pages-cyclic-fix
+++ a/mm/page-writeback.c
@@ -868,9 +868,10 @@ int write_cache_pages(struct address_spa
int done = 0;
struct pagevec pvec;
int nr_pages;
+ pgoff_t writeback_index;
pgoff_t index;
pgoff_t end; /* Inclusive */
- int scanned = 0;
+ int cycled;
int range_whole = 0;
long nr_to_write = wbc->nr_to_write;
@@ -881,14 +882,19 @@ int write_cache_pages(struct address_spa
pagevec_init(&pvec, 0);
if (wbc->range_cyclic) {
- index = mapping->writeback_index; /* Start from prev offset */
+ writeback_index = mapping->writeback_index; /* prev offset */
+ index = writeback_index;
+ if (index == 0)
+ cycled = 1;
+ else
+ cycled = 0;
end = -1;
} else {
index = wbc->range_start >> PAGE_CACHE_SHIFT;
end = wbc->range_end >> PAGE_CACHE_SHIFT;
if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
range_whole = 1;
- scanned = 1;
+ cycled = 1; /* ignore range_cyclic tests */
}
retry:
while (!done && (index <= end) &&
@@ -897,7 +903,6 @@ retry:
min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
unsigned i;
- scanned = 1;
for (i = 0; i < nr_pages; i++) {
struct page *page = pvec.pages[i];
@@ -915,7 +920,11 @@ retry:
continue;
}
- if (!wbc->range_cyclic && page->index > end) {
+ if (page->index > end) {
+ /*
+ * can't be range_cyclic (1st pass) because
+ * end == -1 in that case.
+ */
done = 1;
unlock_page(page);
continue;
@@ -946,13 +955,15 @@ retry:
pagevec_release(&pvec);
cond_resched();
}
- if (!scanned && !done) {
+ if (!cycled) {
/*
+ * range_cyclic:
* We hit the last page and there is more work to be done: wrap
* back to the start of the file
*/
- scanned = 1;
+ cycled = 1;
index = 0;
+ end = writeback_index - 1;
goto retry;
}
if (!wbc->no_nrwrite_index_update) {
_
Patches currently in -mm which might be from npiggin@xxxxxxx are
mm-increase-the-default-mlock-limit-from-32k-to-64k.patch
fs-remove-prepare_write-commit_write.patch
linux-next.patch
mm-dont-mark_page_accessed-in-fault-path.patch
mm-invoke-oom-killer-from-page-fault.patch
mm-invoke-oom-killer-from-page-fault-fix.patch
mm-invoke-oom-killer-from-page-fault-fix-fix-2.patch
mm-write_cache_pages-cyclic-fix.patch
mm-write_cache_pages-cyclic-fix-fix.patch
mm-write_cache_pages-early-loop-termination.patch
mm-write_cache_pages-writepage-error-fix.patch
mm-write_cache_pages-integrity-fix.patch
mm-write_cache_pages-cleanups.patch
mm-write_cache_pages-optimise-page-cleaning.patch
mm-write_cache_pages-terminate-quickly.patch
mm-write_cache_pages-more-terminate-quickly.patch
mm-do_sync_mapping_range-integrity-fix.patch
reiser4.patch
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