]> git.proxmox.com Git - mirror_ubuntu-kernels.git/commit
mm for fs: add truncate_pagecache_range()
authorHugh Dickins <hughd@google.com>
Wed, 28 Mar 2012 21:42:40 +0000 (14:42 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 29 Mar 2012 00:14:35 +0000 (17:14 -0700)
commit623e3db9f9b7d6e7b2a99180f9cf0825c936ab7a
treed8eaa8f1665a048c4318ccd0759775e057792823
parent3748b2f15b06ea1861df39d5e9693dcd6e9542b1
mm for fs: add truncate_pagecache_range()

Holepunching filesystems ext4 and xfs are using truncate_inode_pages_range
but forgetting to unmap pages first (ocfs2 remembers).  This is not really
a bug, since races already require truncate_inode_page() to handle that
case once the page is locked; but it can be very inefficient if the file
being punched happens to be mapped into many vmas.

Provide a drop-in replacement truncate_pagecache_range() which does the
unmapping pass first, handling the awkward mismatch between arguments to
truncate_inode_pages_range() and arguments to unmap_mapping_range().

Note that holepunching does not unmap privately COWed pages in the range:
POSIX requires that we do so when truncating, but it's hard to justify,
difficult to implement without an i_size cutoff, and no filesystem is
attempting to implement it.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Ben Myers <bpm@sgi.com>
Cc: Alex Elder <elder@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
include/linux/mm.h
mm/truncate.c