tree c75be3a413a4fca8c2e0058d75df06a2c22610fa
parent f3a932baa7f65072434f1c04c02c8a4d2746fcfc
author Oleg Drokin <green@linuxhacker.ru> 1465425239 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> 1465507391 -0700

mm/fadvise.c: do not discard partial pages with POSIX_FADV_DONTNEED

I noticed that the logic in the fadvise64_64 syscall is incorrect for
partial pages.  While first page of the region is correctly skipped if
it is partial, the last page of the region is mistakenly discarded.
This leads to problems for applications that read data in
non-page-aligned chunks discarding already processed data between the
reads.

A somewhat misguided application that does something like write(XX bytes
(non-page-alligned)); drop the data it just wrote; repeat gets a
significant penalty in performance as a result.

Link: http://lkml.kernel.org/r/1464917140-1506698-1-git-send-email-green@linuxhacker.ru
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>