We'd like to break out of the loop early in many situations, however the
existing code has been setting mapping->writeback_index past the final page
in the pagevec lookup for cyclic writeback. This is a problem if we don't
process all pages up to the final page.
Currently the code mostly keeps writeback_index reasonable and hacked around
this by not breaking out of the loop or writing pages outside the range in
these cases. Keep track of a real "done index" that enables us to terminate
the loop in a much more flexible manner.
Needed by the subsequent patch to preserve writepage errors, and then further
patches to break out of the loop early for other reasons. However there
are no functional changes with this patch alone.
Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
---
Index: linux-2.6/mm/page-writeback.c
===================================================================
--- linux-2.6.orig/mm/page-writeback.c
+++ linux-2.6/mm/page-writeback.c
@@ -871,6 +871,7 @@ int write_cache_pages(struct address_spa
pgoff_t writeback_index;
pgoff_t index;
pgoff_t end; /* Inclusive */
+ pgoff_t done_index;
int cycled;
int range_whole = 0;
long nr_to_write = wbc->nr_to_write;
@@ -897,6 +898,7 @@ int write_cache_pages(struct address_spa
cycled = 1; /* ignore range_cyclic tests */
}
retry:
+ done_index = index;
while (!done && (index <= end) &&
(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
PAGECACHE_TAG_DIRTY,
@@ -906,6 +908,8 @@ retry:
for (i = 0; i < nr_pages; i++) {
struct page *page = pvec.pages[i];
+ done_index = page->index + 1;
+
/*
* At this point we hold neither mapping->tree_lock nor
* lock on the page itself: the page may be truncated or
@@ -968,7 +972,7 @@ retry:
}
if (!wbc->no_nrwrite_index_update) {
if (wbc->range_cyclic || (range_whole && nr_to_write > 0))
- mapping->writeback_index = index;
+ mapping->writeback_index = done_index;
wbc->nr_to_write = nr_to_write;
}
--
--
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