On 02.10.25 21:39, Stefan Hajnoczi wrote:
Linux block devices require write zeroes alignment whereas files do not.
It may come as a surprise that block devices opened in buffered I/O mode
require the alignment although regular read/write requests do not.
Therefore it is necessary to populate the pwrite_zeroes_alignment field.
Signed-off-by: Stefan Hajnoczi <[email protected]>
---
block/file-posix.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/block/file-posix.c b/block/file-posix.c
index 8c738674ce..05c92c824d 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1602,6 +1602,23 @@ static void raw_refresh_limits(BlockDriverState *bs,
Error **errp)
bs->bl.pdiscard_alignment = dalign;
}
+
+#ifdef __linux__
+ /*
+ * When request_alignment > 1, pwrite_zeroes_alignment does not need to
+ * be set explicitly. When request_alignment == 1, it must be set
+ * explicitly because Linux requires logical block size alignment.
+ */
+ if (bs->bl.request_alignment == 1) {
would "if (!s->needs_alignment) {" be a more visual check? This way reader will
not have to analyze
raw_probe_alignment, and understand that needs_alignment=false is the only path
for block device
to have request_alignment==1.
+ ret = probe_logical_blocksize(s->fd,
+ &bs->bl.pwrite_zeroes_alignment);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret,
+ "Failed to probe logical block size");
+ return;
+ }
+ }
+#endif /* __linux__ */
}
raw_refresh_zoned_limits(bs, &st, errp);
--
Best regards,
Vladimir
