ext4: fix races between buffered IO and collapse / insert range

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commit 32ebffd3bb upstream.

Current code implementing FALLOC_FL_COLLAPSE_RANGE and
FALLOC_FL_INSERT_RANGE is prone to races with buffered writes and page
faults. If buffered write or write via mmap manages to squeeze between
filemap_write_and_wait_range() and truncate_pagecache() in the fallocate
implementations, the written data is simply discarded by
truncate_pagecache() although it should have been shifted.

Fix the problem by moving filemap_write_and_wait_range() call inside
i_mutex and i_mmap_sem. That way we are protected against races with
both buffered writes and page faults.

Signed-off-by: Jan Kara <jack@suse.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

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Jan Kara 2015-12-07 14:31:11 -05:00 • committed by Greg Kroah-Hartman

parent e096ade68c

commit 1f7b7e9a4b

1 changed files with 31 additions and 28 deletions

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fs/ext4/extents.c

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