On Mon, Jul 16, 2018 at 03:52:13PM +0300, Yuval Turgeman wrote:
> When running `kpartx -d`, find_loop_by_file tries to compare the image's
> realpath with the output from loopinfo.lo_name, which may hold only the
> basename of the image, making kpartx exit without finding the loopdev
> for the image.
>
> In case the original comparison fails, this patch will check the image's
> realpath with the loop device's backing_file so that find_loop_by_file
> will return the correct value.
Looks good.
Reviewed-by: Benjamin Marzinski <bmarzins@xxxxxxxxxx>
>
> Signed-off-by: Yuval Turgeman <yturgema@xxxxxxxxxx>
> ---
> kpartx/lopart.c | 30 ++++++++++++++++++++++++++++++
> 1 file changed, 30 insertions(+)
>
> diff --git a/kpartx/lopart.c b/kpartx/lopart.c
> index 69c1eda1..9b652554 100644
> --- a/kpartx/lopart.c
> +++ b/kpartx/lopart.c
> @@ -69,6 +69,8 @@ char *find_loop_by_file(const char *filename)
> struct loop_info loopinfo;
> const char VIRT_BLOCK[] = "/sys/devices/virtual/block";
> char path[PATH_MAX];
> + char bf_path[PATH_MAX];
> + char backing_file[PATH_MAX];
>
> dir = opendir(VIRT_BLOCK);
> if (!dir)
> @@ -122,6 +124,34 @@ char *find_loop_by_file(const char *filename)
> found = realpath(path, NULL);
> break;
> }
> +
> + /*
> + * filename is a realpath, while loopinfo.lo_name may hold just the
> + * basename. If that's the case, try to match filename against the
> + * backing_file entry for this loop entry
> + */
> + if (snprintf(bf_path, PATH_MAX, "%s/%s/loop/backing_file", VIRT_BLOCK,
> + dent->d_name) >= PATH_MAX)
> + continue;
> +
> + fd = open(bf_path, O_RDONLY);
> + if (fd < 0)
> + continue;
> +
> + bytes_read = read(fd, backing_file, sizeof(backing_file) - 1);
> + if (bytes_read <= 0) {
> + close(fd);
> + continue;
> + }
> +
> + close(fd);
> +
> + backing_file[bytes_read-1] = '\0';
> +
> + if (0 == strcmp(filename, backing_file)) {
> + found = realpath(path, NULL);
> + break;
> + }
> }
> closedir(dir);
> return found;
> --
> 2.17.1
>
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