From: Hugh Dickins <hughd@google.com>
Date: Tue, 29 May 2012 22:06:40 +0000 (-0700)
Subject: tmpfs: support fallocate FALLOC_FL_PUNCH_HOLE
X-Git-Tag: v3.5-rc1~49^2~130
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=83e4fa9c16e4af7122e31be3eca5d57881d236fe;p=pandora-kernel.git

tmpfs: support fallocate FALLOC_FL_PUNCH_HOLE

tmpfs has supported hole-punching since 2.6.16, via
madvise(,,MADV_REMOVE).

But nowadays fallocate(,FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE,,) is
the agreed way to punch holes.

So add shmem_fallocate() to support that, and tweak shmem_truncate_range()
to support partial pages at both the beginning and end of range (never
needed for madvise, which demands rounded addr and rounds up length).

Based-on-patch-by: Cong Wang <amwang@redhat.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Cong Wang <amwang@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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