[Qemu-devel] [PATCH v5 2/5] raw-posix: Refactor logical block size detection.

[Ekaterina Tumanova <tumanova@linux.vnet.ibm.com>]

1. Move block size detection into dedicated function.
2. Select exactly one IOCTL that detects blocksize, specific to the host OS.

Signed-off-by: Ekaterina Tumanova <tumanova@linux.vnet.ibm.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
---
 block/raw-posix.c | 41 ++++++++++++++++++++++++-----------------
 1 file changed, 24 insertions(+), 17 deletions(-)

diff --git a/block/raw-posix.c b/block/raw-posix.c
index e51293a..38172ca 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -217,11 +217,31 @@ static int raw_normalize_devicepath(const char **filename)
 }
 #endif
 
+/*
+ * Get logical block size via ioctl. On success return 0. Otherwise -errno.
+ */
+static int probe_logical_blocksize(int fd, unsigned int *sector_size)
+{
+#if defined(BLKSSZGET)
+#  define SECTOR_SIZE BLKSSZGET
+#elif defined(DKIOCGETBLOCKSIZE)
+#  define SECTOR_SIZE DKIOCGETBLOCKSIZE
+#elif defined(DIOCGSECTORSIZE)
+#  define SECTOR_SIZE DIOCGSECTORSIZE
+#else
+    return -ENOTSUP
+#endif
+    if (ioctl(fd, SECTOR_SIZE, sector_size) < 0) {
+        return -errno;
+    }
+    return 0;
+#undef SECTOR_SIZE
+}
+
 static void raw_probe_alignment(BlockDriverState *bs, int fd, Error **errp)
 {
     BDRVRawState *s = bs->opaque;
     char *buf;
-    unsigned int sector_size;
 
     /* For /dev/sg devices the alignment is not really used.
        With buffered I/O, we don't have any restrictions. */
@@ -231,25 +251,12 @@ static void raw_probe_alignment(BlockDriverState *bs, int fd, Error **errp)
         return;
     }
 
-    /* Try a few ioctls to get the right size */
     bs->request_alignment = 0;
     s->buf_align = 0;
-
-#ifdef BLKSSZGET
-    if (ioctl(fd, BLKSSZGET, &sector_size) >= 0) {
-        bs->request_alignment = sector_size;
-    }
-#endif
-#ifdef DKIOCGETBLOCKSIZE
-    if (ioctl(fd, DKIOCGETBLOCKSIZE, &sector_size) >= 0) {
-        bs->request_alignment = sector_size;
+    /* Let's try to use the logical blocksize for the alignment. */
+    if (probe_logical_blocksize(fd, &bs->request_alignment) < 0) {
+        bs->request_alignment = 0;
     }
-#endif
-#ifdef DIOCGSECTORSIZE
-    if (ioctl(fd, DIOCGSECTORSIZE, &sector_size) >= 0) {
-        bs->request_alignment = sector_size;
-    }
-#endif
 #ifdef CONFIG_XFS
     if (s->is_xfs) {
         struct dioattr da;
-- 
1.8.5.5