In some cases we can reach ext4_da_writepages() with
wbc->nr_to_write == LONG_MAX, !range_cyclic, and range_whole=1;
in this case we will try to bump it up by a factor of 8, which
leads to a desired_nr_to_write value of -8.
We still get through the logic without actually changing
wbc->nr_to_write because the other tests which would change
it don't trip due to the negative value, but it seems dangerous
to overflow desired_nr_to_write in the interim, it's not an
obvious situation.
Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
---
(V2 minor commit message edits)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 93497f6..2e72a4a 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3004,9 +3004,11 @@ static int ext4_da_writepages(struct address_space *mapping,
* sbi->max_writeback_mb_bump whichever is smaller.
*/
max_pages = sbi->s_max_writeback_mb_bump << (20 - PAGE_CACHE_SHIFT);
- if (!range_cyclic && range_whole)
- desired_nr_to_write = wbc->nr_to_write * 8;
- else
+ if (!range_cyclic && range_whole) {
+ desired_nr_to_write = wbc->nr_to_write;
+ if (desired_nr_to_write != LONG_MAX)
+ desired_nr_to_write *= 8;
+ } else
desired_nr_to_write = ext4_num_dirty_pages(inode, index,
max_pages);
if (desired_nr_to_write > max_pages)
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