These patches eliminate data writes completely on Linux if fallocate
FALLOC_FL_ZERO_RANGE or FALLOC_FL_PUNCH_HOLE are supported on
underlying filesystem.
I have performed several tests with non-aligned fallocate calls and
in all cases (with non-aligned fallocates) Linux performs fine, i.e.
areas are zeroed correctly. Checks were made on
Linux 3.16.0-28-generic #38-Ubuntu SMP
This should seriously increase performance of bdrv_write_zeroes
Changes from v3:
- dropped original patch 1, equivalent stuff was merged already
- reordered patches as suggested by Fam
- fixes spelling errors as suggested by Fam
- fixed not initialized value in handle_aiocb_write_zeroes
- fixed wrong error processing from do_fallocate(FALLOC_FL_ZERO_RANGE)
Changes from v2:
- added Peter Lieven to CC
- added CONFIG_FALLOCATE check to call do_fallocate in patch 7
- dropped patch 1 as NACK-ed
- added processing of very large data areas in bdrv_co_write_zeroes (new
patch 1)
- set bl.max_write_zeroes to INT_MAX in raw-posix.c for regular files
(new patch 8)
Signed-off-by: Denis V. Lunev <d...@openvz.org>
CC: Kevin Wolf <kw...@redhat.com>
CC: Stefan Hajnoczi <stefa...@redhat.com>
CC: Peter Lieven <p...@kamp.de>
CC: Fam Zheng <f...@redhat.com>
