kvm tools: Add debug info for disk_image__{read, write}

Print debug info when read/write error occurs

Signed-off-by: Asias He <asias.hejun@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

diff --git a/tools/kvm/disk/core.c b/tools/kvm/disk/core.c
index f3dd0bb34cac43f5aa51b3845d541d3897623a5c..b229f83bb599731135b1c39edb48e611e9ece366 100644 (file)
--- a/tools/kvm/disk/core.c
+++ b/tools/kvm/disk/core.c
@@ -84,40 +84,79 @@ int disk_image__close(struct disk_image *disk)
        return 0;
 }
 
-/* Fill iov with disk data, starting from sector 'sector'. Return amount of bytes read. */
+/*
+ * Fill iov with disk data, starting from sector 'sector'.
+ * Return amount of bytes read.
+ */
 ssize_t disk_image__read(struct disk_image *disk, u64 sector, const struct iovec *iov, int iovcount)
 {
-       u64 first_sector = sector;
+       ssize_t total = 0;
+       ssize_t nr;
 
-       if (disk->ops->read_sector_iov)
-               return disk->ops->read_sector_iov(disk, sector, iov, iovcount);
-
-       while (iovcount--) {
-               if (disk->ops->read_sector(disk, sector, iov->iov_base, iov->iov_len) < 0)
+       if (disk->ops->read_sector_iov) {
+               /*
+                * Try mulitple buffer based operation first
+                */
+               total           = disk->ops->read_sector_iov(disk, sector, iov, iovcount);
+               if (total < 0) {
+                       info("disk_image__read error: total=%ld\n", (long)total);
                        return -1;
-
-               sector += iov->iov_len >> SECTOR_SHIFT;
-               iov++;
-       }
-
-       return (sector - first_sector) << SECTOR_SHIFT;
+               }
+       } else if (disk->ops->read_sector) {
+               /*
+                * Fallback to single buffer based operation
+                */
+               while (iovcount--) {
+                       nr      = disk->ops->read_sector(disk, sector, iov->iov_base, iov->iov_len);
+                       if (nr != (ssize_t)iov->iov_len) {
+                               info("disk_image__read error: nr = %ld iov_len=%ld\n", (long)nr, (long)iov->iov_len);
+                               return -1;
+                       }
+                       sector  += iov->iov_len >> SECTOR_SHIFT;
+                       iov++;
+                       total   += nr;
+               }
+       } else
+               die("No disk image operation for read\n");
+
+       return total;
 }
 
-/* Write iov to disk, starting from sector 'sector'. Return amount of bytes written. */
+/*
+ * Write iov to disk, starting from sector 'sector'.
+ * Return amount of bytes written.
+ */
 ssize_t disk_image__write(struct disk_image *disk, u64 sector, const struct iovec *iov, int iovcount)
 {
-       u64 first_sector = sector;
+       ssize_t total = 0;
+       ssize_t nr;
 
-       if (disk->ops->write_sector_iov)
-               return disk->ops->write_sector_iov(disk, sector, iov, iovcount);
-
-       while (iovcount--) {
-               if (disk->ops->write_sector(disk, sector, iov->iov_base, iov->iov_len) < 0)
+       if (disk->ops->write_sector_iov) {
+               /*
+                * Try writev based operation first
+                */
+               total = disk->ops->write_sector_iov(disk, sector, iov, iovcount);
+               if (total < 0) {
+                       info("disk_image__write error: total=%ld\n", (long)total);
                        return -1;
-
-               sector += iov->iov_len >> SECTOR_SHIFT;
-               iov++;
-       }
-
-       return (sector - first_sector) << SECTOR_SHIFT;
+               }
+       } else if (disk->ops->write_sector) {
+               /*
+                * Fallback to single buffer based operation
+                */
+               while (iovcount--) {
+                       nr       = disk->ops->write_sector(disk, sector, iov->iov_base, iov->iov_len);
+                       if (nr != (ssize_t)iov->iov_len) {
+                               info("disk_image__write error: nr=%ld iov_len=%ld\n", (long)nr, (long)iov->iov_len);
+                               return -1;
+                       }
+
+                       sector  += iov->iov_len >> SECTOR_SHIFT;
+                       iov++;
+                       total   += nr;
+               }
+       } else
+               die("No disk image operation for read\n");
+
+       return total;
 }