filemap: Correct the conditions for marking a folio as accessed
authorMatthew Wilcox (Oracle) <willy@infradead.org>
Fri, 10 Jun 2022 18:44:41 +0000 (14:44 -0400)
committerMatthew Wilcox (Oracle) <willy@infradead.org>
Mon, 20 Jun 2022 20:37:45 +0000 (16:37 -0400)
commit5ccc944dce3df5fd2fd683a7df4fd49d1068eba2
tree8c1cf8edf223d2cec883a700bc3ce8106f39beb2
parent78ca55889a549a9a194c6ec666836329b774ab6d
filemap: Correct the conditions for marking a folio as accessed

We had an off-by-one error which meant that we never marked the first page
in a read as accessed.  This was visible as a slowdown when re-reading
a file as pages were being evicted from cache too soon.  In reviewing
this code, we noticed a second bug where a multi-page folio would be
marked as accessed multiple times when doing reads that were less than
the size of the folio.

Abstract the comparison of whether two file positions are in the same
folio into a new function, fixing both of these bugs.

Reported-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
mm/filemap.c