Am 22.09.2014 um 17:36 hat Max Reitz geschrieben:
> 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 <kw...@redhat.com>
> Signed-off-by: Max Reitz <mre...@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);
This assertion can be triggered if another process truncates the file in
the background after it has been opened (bdrv_getlength() usually uses
the cached value, so this race condition isn't even hard to reproduce).
Kevin
> 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);
bdrv_getlength() can fail.
> + 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;
> + }
Kevin
