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block/file-posix: Reduce xfsctl() use
This patch removes xfs_write_zeroes() and xfs_discard(). Both functions have been added just before the same feature was present through fallocate(): - fallocate() has supported PUNCH_HOLE for XFS since Linux 2.6.38 (March 2011); xfs_discard() was added in December 2010. - fallocate() has supported ZERO_RANGE for XFS since Linux 3.15 (June 2014); xfs_write_zeroes() was added in November 2013. Nowadays, all systems that qemu runs on should support both fallocate() features (RHEL 7's kernel does). xfsctl() is still useful for getting the request alignment for O_DIRECT, so this patch does not remove our dependency on it completely. Note that xfs_write_zeroes() had a bug: It calls ftruncate() when the file is shorter than the specified range (because ZERO_RANGE does not increase the file length). ftruncate() may yield and then discard data that parallel write requests have written past the EOF in the meantime. Dropping the function altogether fixes the bug. Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Fixes: 50ba5b2 Reported-by: Lukáš Doktor <ldoktor@redhat.com> Cc: qemu-stable@nongnu.org Signed-off-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Stefano Garzarella <sgarzare@redhat.com> Reviewed-by: John Snow <jsnow@redhat.com> Tested-by: Stefano Garzarella <sgarzare@redhat.com> Tested-by: John Snow <jsnow@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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