block: workaround for unaligned byte range in fallocate()

Revert the commit 118f99442d 'block/io.c: fix for the allocation failure'
and use better error handling for file systems that do not support
fallocate() for an unaligned byte range. Allow falling back to pwrite
in case fallocate() returns EINVAL.

Suggested-by: Kevin Wolf <kwolf@redhat.com>
Suggested-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Denis V. Lunev <den@openvz.org>
Message-Id: <1566913973-15490-1-git-send-email-andrey.shinkevich@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

2 files changed, 8 insertions, 1 deletions

diff --git a/block/file-posix.c b/block/file-posix.c
index 71f168e..87c5a4c 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1588,6 +1588,13 @@ static int handle_aiocb_write_zeroes(void *opaque)
     if (s->has_write_zeroes) {
         int ret = do_fallocate(s->fd, FALLOC_FL_ZERO_RANGE,
                                aiocb->aio_offset, aiocb->aio_nbytes);
+        if (ret == -EINVAL) {
+            /*
+             * Allow falling back to pwrite for file systems that
+             * do not support fallocate() for an unaligned byte range.
+             */
+            return -ENOTSUP;
+        }
         if (ret == 0 || ret != -ENOTSUP) {
             return ret;
         }
diff --git a/block/io.c b/block/io.c
index 0fa10831..16a598f 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1746,7 +1746,7 @@ static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
             assert(!bs->supported_zero_flags);
         }
 
-        if (ret < 0 && !(flags & BDRV_REQ_NO_FALLBACK)) {
+        if (ret == -ENOTSUP && !(flags & BDRV_REQ_NO_FALLBACK)) {
             /* Fall back to bounce buffer if write zeroes is unsupported */
             BdrvRequestFlags write_flags = flags & ~BDRV_REQ_ZERO_WRITE;