ext4: allocate entire range in zero range

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commit 0f2af21aae upstream.

Currently there is a bug in zero range code which causes zero range
calls to only allocate block aligned portion of the range, while
ignoring the rest in some cases.

In some cases, namely if the end of the range is past i_size, we do
attempt to preallocate the last nonaligned block. However this might
cause kernel to BUG() in some carefully designed zero range requests
on setups where page size > block size.

Fix this problem by first preallocating the entire range, including
the nonaligned edges and converting the written extents to unwritten
in the next step. This approach will also give us the advantage of
having the range to be as linearly contiguous as possible.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: Moritz Muehlenhoff <jmm@debian.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

...

This commit is contained in:

Lukas Czerner 2015-04-03 00:09:13 -04:00 • committed by Luis Henriques

parent 9ad1354755

commit 7e11ae290d

1 changed files with 19 additions and 12 deletions

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fs/ext4/extents.c

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