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authorNick Piggin <npiggin@suse.de>2009-01-06 14:39:04 -0800
committerGreg Kroah-Hartman <gregkh@suse.de>2009-01-24 16:41:46 -0800
commit8c265555fedf2bab5f045f65b43ed9160cc808b7 (patch)
treebc6787ad05caa48428f72bb75e954a1099e99006
parentc459c4d854842c4bd3a118b7d300da5f16fee6c2 (diff)
mm: write_cache_pages cyclic fix
commit 31a12666d8f0c22235297e1c1575f82061480029 upstream. 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@suse.de> Cc: Chris Mason <chris.mason@oracle.com> Cc: Dave Chinner <david@fromorbit.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--mm/page-writeback.c25
1 files changed, 18 insertions, 7 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 2970e35fd03..eb277bdd4c5 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -868,9 +868,10 @@ int write_cache_pages(struct address_space *mapping,
int done = 0;
struct pagevec pvec;
int nr_pages;
+ pgoff_t uninitialized_var(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_space *mapping,
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) {