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authorNick Piggin <npiggin@suse.de>2009-01-06 14:39:04 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-01-06 15:58:59 -0800
commit31a12666d8f0c22235297e1c1575f82061480029 (patch)
tree89106848d2072278cc9338b091ad059db460420f
parent38c8e6180939e5619140b2e9e479cb26029ff8b1 (diff)
mm: write_cache_pages cyclic fix
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>
-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 2970e35fd03f..eb277bdd4c5d 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) {