[Qemu-devel] [PATCH v2 1/2] raw-posix: Fix raw_co_get_block_status() after EOF

[Max Reitz <mreitz@redhat.com>]

As its comment states, raw_co_get_block_status() should unconditionally
return 0 and set *pnum to 0 for after EOF.

An assertion after lseek(..., SEEK_HOLE) tried to catch this case by
asserting that errno != -ENXIO (which would indicate a position after
the EOF); but it should be errno != ENXIO instead. Fix this, too.

Additionally, nb_sectors should be clamped against the image end. This
was probably not an issue if FIEMAP or SEEK_HOLE/SEEK_DATA worked, but
the fallback did not take this case into account.

Reported-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 block/raw-posix.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/block/raw-posix.c b/block/raw-posix.c
index a253697..dd57992 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -1509,9 +1509,9 @@ static int64_t try_seek_hole(BlockDriverState *bs, off_t start, off_t *data,
 
     *hole = lseek(s->fd, start, SEEK_HOLE);
     if (*hole == -1) {
-        /* -ENXIO indicates that sector_num was past the end of the file.
+        /* ENXIO indicates that sector_num was past the end of the file.
          * There is a virtual hole there.  */
-        assert(errno != -ENXIO);
+        assert(errno != ENXIO);
 
         return -errno;
     }
@@ -1552,6 +1552,7 @@ static int64_t coroutine_fn raw_co_get_block_status(BlockDriverState *bs,
                                                     int nb_sectors, int *pnum)
 {
     off_t start, data = 0, hole = 0;
+    int64_t total_size;
     int64_t ret;
 
     ret = fd_open(bs);
@@ -1560,6 +1561,13 @@ static int64_t coroutine_fn raw_co_get_block_status(BlockDriverState *bs,
     }
 
     start = sector_num * BDRV_SECTOR_SIZE;
+    total_size = bdrv_getlength(bs);
+    if (start >= total_size) {
+        *pnum = 0;
+        return 0;
+    } else if (start + nb_sectors * BDRV_SECTOR_SIZE > total_size) {
+        nb_sectors = (total_size - start) / BDRV_SECTOR_SIZE;
+    }
 
     ret = try_fiemap(bs, start, &data, &hole, nb_sectors, pnum);
     if (ret < 0) {
-- 
2.1.0