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SubjectRe: [RFC PATCH] mm: Stop filemap_read() from grabbing a superfluous page
On Thu, Oct 07, 2021 at 01:01:48PM +0100, David Howells wrote:
> Under some circumstances, filemap_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.
>
> filemap_read() *does* check for this, but only after it has already done
> the allocation and I/O. Fix this by checking before calling
> filemap_get_pages() also.
>
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Kent Overstreet <kent.overstreet@gmail.com>
> cc: Matthew Wilcox (Oracle) <willy@infradead.org>
> cc: linux-mm@kvack.org
> cc: linux-fsdevel@vger.kernel.org
> Link: https://lore.kernel.org/r/160588481358.3465195.16552616179674485179.stgit@warthog.procyon.org.uk/

Acked-by: Kent Overstreet <kent.overstreet@gmail.com>

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