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mm: account skipped entries to avoid looping in find_get_pages

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The found entries by find_get_pages() could be all swap entries.  In
this case we skip the entries, but make sure the skipped entries are
accounted, so we don't keep looping.

Using nr_found > nr_skip to simplify code as suggested by Eric.

Reported-and-tested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Shaohua Li 2011-09-15 08:45:19 +08:00 committed by Linus Torvalds
parent 4f5b04800a
commit cc39c6a9bb
1 changed files with 4 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

6
mm/filemap.c
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@ -827,13 +827,14 @@ unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
{ {
unsigned int i; unsigned int i;
unsigned int ret; unsigned int ret;
unsigned int nr_found; unsigned int nr_found, nr_skip;
rcu_read_lock(); rcu_read_lock();
restart: restart:
nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
(void ***)pages, NULL, start, nr_pages); (void ***)pages, NULL, start, nr_pages);
ret = 0; ret = 0;
nr_skip = 0;
for (i = 0; i < nr_found; i++) { for (i = 0; i < nr_found; i++) {
struct page *page; struct page *page;
repeat: repeat:
@ -856,6 +857,7 @@ unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
* here as an exceptional entry: so skip over it - * here as an exceptional entry: so skip over it -
* we only reach this from invalidate_mapping_pages(). * we only reach this from invalidate_mapping_pages().
*/ */
nr_skip++;
continue; continue;
} }
@ -876,7 +878,7 @@ unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
* If all entries were removed before we could secure them, * If all entries were removed before we could secure them,
* try again, because callers stop trying once 0 is returned. * try again, because callers stop trying once 0 is returned.
*/ */
if (unlikely(!ret && nr_found)) if (unlikely(!ret && nr_found > nr_skip))
goto restart; goto restart;
rcu_read_unlock(); rcu_read_unlock();
return ret; return ret;