[Qemu-devel] [PATCH 1/5] [block]: Add top level BSG support

["Nicholas A. Bellinger" <nab@linux-iscsi.org>]

From: Nicholas Bellinger <nab@linux-iscsi.org>

This patch adds top level BSG support to QEMU-KVM block and adds the
BDS_* prefixed defines for SG_IO and BSG.

It adds the BDS_SCSI_GENERIC and BDS_BSG assignments in block/raw-posix.c:hdev_open()
using S_ISCHR() and major(st.st_rdev) in order to determine when we are dealing with
scsi-generic or scsi-bsg backstores.

It also adds a special case BSG check in find_protocol() using the BSG
major in order to avoid the strchr() for ':' as we expect filenames to
contain /dev/bsg/H:C:T:L.

This path also adds a struct BlockDriverState->fd to save a opened file descriptor
with format_name = 'raw' for use by scsi-bsg.

Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>
---
 block.c           |   23 ++++++++++++++++++++---
 block.h           |    1 +
 block/raw-posix.c |   17 +++++++++++++++--
 block_int.h       |    5 +++++
 4 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/block.c b/block.c
index 88dbc00..3cd18ec 100644
--- a/block.c
+++ b/block.c
@@ -285,8 +285,12 @@ static BlockDriver *find_protocol(const char *filename)
 {
     BlockDriver *drv1;
     char protocol[128];
-    int len;
+    int len, bsg = 0;
     const char *p;
+#if defined(__linux__)
+    struct stat st;
+#endif
+
 
     /* TODO Drivers without bdrv_file_open must be specified explicitly */
 
@@ -296,7 +300,15 @@ static BlockDriver *find_protocol(const char *filename)
         return bdrv_find_format("file");
 #endif
     p = strchr(filename, ':');
-    if (!p) {
+#if defined(__linux__)
+    if (stat(filename, &st) < 0)
+        return NULL;
+    /* This is not yet defined in include/linux/major.h.. */
+    if (S_ISCHR(st.st_mode) && major(st.st_rdev) == 254)
+        bsg = 1;
+#endif
+
+    if (!p || bsg) {
         drv1 = find_hdev_driver(filename);
         if (!drv1) {
             drv1 = bdrv_find_format("file");
@@ -1209,7 +1221,12 @@ int bdrv_is_read_only(BlockDriverState *bs)
 
 int bdrv_is_sg(BlockDriverState *bs)
 {
-    return bs->sg;
+    return bs->sg == BDS_SCSI_GENERIC;
+}
+
+int bdrv_is_bsg(BlockDriverState *bs)
+{
+    return bs->sg == BDS_BSG;
 }
 
 int bdrv_enable_write_cache(BlockDriverState *bs)
diff --git a/block.h b/block.h
index f87d24e..4faeedc 100644
--- a/block.h
+++ b/block.h
@@ -146,6 +146,7 @@ int bdrv_get_translation_hint(BlockDriverState *bs);
 int bdrv_is_removable(BlockDriverState *bs);
 int bdrv_is_read_only(BlockDriverState *bs);
 int bdrv_is_sg(BlockDriverState *bs);
+int bdrv_is_bsg(BlockDriverState *bs);
 int bdrv_enable_write_cache(BlockDriverState *bs);
 int bdrv_is_inserted(BlockDriverState *bs);
 int bdrv_media_changed(BlockDriverState *bs);
diff --git a/block/raw-posix.c b/block/raw-posix.c
index 1515ca9..d349109 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -52,6 +52,7 @@
 #include <sys/ioctl.h>
 #include <linux/cdrom.h>
 #include <linux/fd.h>
+#include <linux/major.h>
 #endif
 #if defined (__FreeBSD__) || defined(__FreeBSD_kernel__)
 #include <signal.h>
@@ -843,6 +844,9 @@ static int hdev_probe_device(const char *filename)
 static int hdev_open(BlockDriverState *bs, const char *filename, int flags)
 {
     BDRVRawState *s = bs->opaque;
+#if defined(__linux__)
+    struct stat st;
+#endif
 
 #ifdef CONFIG_COCOA
     if (strstart(filename, "/dev/cdrom", NULL)) {
@@ -873,8 +877,17 @@ static int hdev_open(BlockDriverState *bs, const char *filename, int flags)
 
     s->type = FTYPE_FILE;
 #if defined(__linux__)
-    if (strstart(filename, "/dev/sg", NULL)) {
-        bs->sg = 1;
+    if (stat(filename, &st) < 0) {
+        printf("stat() failed errno: %d\n", errno);
+        return -1;
+    }
+    if (S_ISCHR(st.st_mode)) {
+        if (major(st.st_rdev) == SCSI_GENERIC_MAJOR) {
+            bs->sg = BDS_SCSI_GENERIC;
+        } else if (major(st.st_rdev) == 254) {
+            /* This is not yet defined in include/linux/major.h.. */
+            bs->sg = BDS_BSG;
+        }
     }
 #endif
 
diff --git a/block_int.h b/block_int.h
index 1a7240c..74bcb1a 100644
--- a/block_int.h
+++ b/block_int.h
@@ -40,6 +40,10 @@
 #define BLOCK_OPT_CLUSTER_SIZE  "cluster_size"
 #define BLOCK_OPT_PREALLOC      "preallocation"
 
+#define BDS_NONE            0
+#define BDS_SCSI_GENERIC    1
+#define BDS_BSG             2
+
 typedef struct AIOPool {
     void (*cancel)(BlockDriverAIOCB *acb);
     int aiocb_size;
@@ -141,6 +145,7 @@ struct BlockDriverState {
     int encrypted; /* if true, the media is encrypted */
     int valid_key; /* if true, a valid encryption key has been set */
     int sg;        /* if true, the device is a /dev/sg* */
+    int fd;        /* Used for BSG file descriptor */
     /* event callback when inserting/removing */
     void (*change_cb)(void *opaque);
     void *change_opaque;
-- 
1.5.6.5