block: use fallocate(FALLOC_FL_ZERO_RANGE) in handle_aiocb_write_zeroes
This efficiently writes zeroes on Linux if the kernel is capable enough. FALLOC_FL_ZERO_RANGE correctly handles all cases, including and not including file expansion. CC: Kevin Wolf <kwolf@redhat.com> CC: Stefan Hajnoczi <stefanha@redhat.com> CC: Peter Lieven <pl@kamp.de> CC: Fam Zheng <famz@redhat.com> Signed-off-by: Denis V. Lunev <den@openvz.org> Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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			@ -60,7 +60,7 @@
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#define FS_NOCOW_FL                     0x00800000 /* Do not cow file */
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#endif
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#endif
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#ifdef CONFIG_FALLOCATE_PUNCH_HOLE
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#if defined(CONFIG_FALLOCATE_PUNCH_HOLE) || defined(CONFIG_FALLOCATE_ZERO_RANGE)
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#include <linux/falloc.h>
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#endif
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#if defined (__FreeBSD__) || defined(__FreeBSD_kernel__)
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			@ -902,7 +902,7 @@ static int translate_err(int err)
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    return err;
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}
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#if defined(CONFIG_FALLOCATE_PUNCH_HOLE)
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#if defined(CONFIG_FALLOCATE_PUNCH_HOLE) || defined(CONFIG_FALLOCATE_ZERO_RANGE)
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static int do_fallocate(int fd, int mode, off_t offset, off_t len)
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{
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    do {
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			@ -954,6 +954,17 @@ static ssize_t handle_aiocb_write_zeroes(RawPosixAIOData *aiocb)
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    }
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#endif
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#ifdef CONFIG_FALLOCATE_ZERO_RANGE
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    if (s->has_write_zeroes) {
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        int ret = do_fallocate(s->fd, FALLOC_FL_ZERO_RANGE,
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                               aiocb->aio_offset, aiocb->aio_nbytes);
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        if (ret == 0 || ret != -ENOTSUP) {
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            return ret;
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        }
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        s->has_write_zeroes = false;
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    }
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#endif
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    return -ENOTSUP;
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}
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			@ -3335,6 +3335,22 @@ if compile_prog "" "" ; then
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  fallocate_punch_hole=yes
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fi
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# check that fallocate supports range zeroing inside the file
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fallocate_zero_range=no
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cat > $TMPC << EOF
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#include <fcntl.h>
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#include <linux/falloc.h>
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int main(void)
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{
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    fallocate(0, FALLOC_FL_ZERO_RANGE, 0, 0);
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    return 0;
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}
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EOF
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if compile_prog "" "" ; then
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  fallocate_zero_range=yes
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fi
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# check for posix_fallocate
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posix_fallocate=no
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cat > $TMPC << EOF
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			@ -4567,6 +4583,9 @@ fi
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if test "$fallocate_punch_hole" = "yes" ; then
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  echo "CONFIG_FALLOCATE_PUNCH_HOLE=y" >> $config_host_mak
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fi
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if test "$fallocate_zero_range" = "yes" ; then
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  echo "CONFIG_FALLOCATE_ZERO_RANGE=y" >> $config_host_mak
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fi
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if test "$posix_fallocate" = "yes" ; then
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  echo "CONFIG_POSIX_FALLOCATE=y" >> $config_host_mak
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fi
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