Under some circumstances, generic_file_buffered_read() will allocate sufficient pages to read to the end of the file, call readahead/readpages on them and copy the data over - and then it will allocate another page at the EOF and call readpage on that and then ignore it. This is unnecessary and a waste of time and resources.
Catch the overallocation in the "no_cached_page:" part and prevent it from happening. Signed-off-by: David Howells <[email protected]> --- mm/filemap.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/filemap.c b/mm/filemap.c index cfb753955e36..5a63aa1dd71e 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2447,6 +2447,8 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb, * Ok, it wasn't cached, so we need to create a new * page.. */ + if ((index << PAGE_SHIFT) >= i_size_read(inode)) + goto out; page = page_cache_alloc(mapping); if (!page) { error = -ENOMEM;
