On 5/15/23 12:04 PM, Stefan Hajnoczi wrote:
> From: Sam Li <faithilikerun@xxxxxxxxx>
>
> Use get_sysfs_str_val() to get the string value of device
> zoned model. Then get_sysfs_zoned_model() can convert it to
> BlockZoneModel type of QEMU.
>
> Use get_sysfs_long_val() to get the long value of zoned device
> information.
Hi Stefan, Sam,
I am having an issue on s390x using virtio-blk-{pci,ccw} backed by an NVMe partition, and I've bisected the root cause to this commit.
I noticed that tests which use the partition e.g. /dev/nvme0n1p1 as a backing device would fail, but those that use the namespace e.g. /dev/nvme0n1 would still succeed. The root issue appears to be that the block device associated with the partition does not have a "max_segments" attribute, and prior to this patch hdev_get_max_segment() would return -ENOENT in this case. After this patch, however, QEMU is instead crashing. It looks like g_file_get_contents is returning 0 with a len == 0 if the specified sysfs path does not exist. The following diff on top seems to resolve the issue for me:
diff --git a/block/file-posix.c b/block/file-posix.c
index 0ab158efba2..eeb0247c74e 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1243,7 +1243,7 @@ static int get_sysfs_str_val(struct stat *st, const char *attribute,
major(st->st_rdev), minor(st->st_rdev),
attribute);
ret = g_file_get_contents(sysfspath, val, &len, NULL);
- if (ret == -1) {
+ if (ret == -1 || len == 0) {
return -ENOENT;
}
>
> Signed-off-by: Sam Li <faithilikerun@xxxxxxxxx>
> Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
> Reviewed-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
> Reviewed-by: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>
> Reviewed-by: Dmitry Fomichev <dmitry.fomichev@xxxxxxx>
> Acked-by: Kevin Wolf <kwolf@xxxxxxxxxx>
> Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
> Message-id: 20230508045533.175575-3-faithilikerun@xxxxxxxxx
> Message-id: 20230324090605.28361-3-faithilikerun@xxxxxxxxx
> [Adjust commit message prefix as suggested by Philippe Mathieu-Daudé
> <philmd@xxxxxxxxxx>.
> --Stefan]
> Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
> ---
> include/block/block_int-common.h | 3 +
> block/file-posix.c | 135 ++++++++++++++++++++++---------
> 2 files changed, 100 insertions(+), 38 deletions(-)
>
> diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h
> index 4909876756..c7ca5a83e9 100644
> --- a/include/block/block_int-common.h
> +++ b/include/block/block_int-common.h
> @@ -862,6 +862,9 @@ typedef struct BlockLimits {
> * an explicit monitor command to load the disk inside the guest).
> */
> bool has_variable_length;
> +
> + /* device zone model */
> + BlockZoneModel zoned;
> } BlockLimits;
>
> typedef struct BdrvOpBlocker BdrvOpBlocker;
> diff --git a/block/file-posix.c b/block/file-posix.c
> index c7b723368e..97c597a2a0 100644
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -1202,15 +1202,89 @@ static int hdev_get_max_hw_transfer(int fd, struct stat *st)
> #endif
> }
>
> -static int hdev_get_max_segments(int fd, struct stat *st)
> +/*
> + * Get a sysfs attribute value as character string.
> + */
> +#ifdef CONFIG_LINUX
> +static int get_sysfs_str_val(struct stat *st, const char *attribute,
> + char **val) {
> + g_autofree char *sysfspath = NULL;
> + int ret;
> + size_t len;
> +
> + if (!S_ISBLK(st->st_mode)) {
> + return -ENOTSUP;
> + }
> +
> + sysfspath = g_strdup_printf("/sys/dev/block/%u:%u/queue/%s",
> + major(st->st_rdev), minor(st->st_rdev),
> + attribute);
> + ret = g_file_get_contents(sysfspath, val, &len, NULL);
> + if (ret == -1) {
> + return -ENOENT;
> + }
> +
> + /* The file is ended with '\n' */
> + char *p;
> + p = *val;
> + if (*(p + len - 1) == '\n') {
> + *(p + len - 1) = '\0';
> + }
> + return ret;
> +}
> +#endif
> +
> +static int get_sysfs_zoned_model(struct stat *st, BlockZoneModel *zoned)
> {
> + g_autofree char *val = NULL;
> + int ret;
> +
> + ret = get_sysfs_str_val(st, "zoned", &val);
> + if (ret < 0) {
> + return ret;
> + }
> +
> + if (strcmp(val, "host-managed") == 0) {
> + *zoned = BLK_Z_HM;
> + } else if (strcmp(val, "host-aware") == 0) {
> + *zoned = BLK_Z_HA;
> + } else if (strcmp(val, "none") == 0) {
> + *zoned = BLK_Z_NONE;
> + } else {
> + return -ENOTSUP;
> + }
> + return 0;
> +}
> +
> +/*
> + * Get a sysfs attribute value as a long integer.
> + */
> #ifdef CONFIG_LINUX
> - char buf[32];
> +static long get_sysfs_long_val(struct stat *st, const char *attribute)
> +{
> + g_autofree char *str = NULL;
> const char *end;
> - char *sysfspath = NULL;
> + long val;
> + int ret;
> +
> + ret = get_sysfs_str_val(st, attribute, &str);
> + if (ret < 0) {
> + return ret;
> + }
> +
> + /* The file is ended with '\n', pass 'end' to accept that. */
> + ret = qemu_strtol(str, &end, 10, &val);
> + if (ret == 0 && end && *end == '\0') {
> + ret = val;
> + }
> + return ret;
> +}
> +#endif
> +
> +static int hdev_get_max_segments(int fd, struct stat *st)
> +{
> +#ifdef CONFIG_LINUX
> int ret;
> - int sysfd = -1;
> - long max_segments;
>
> if (S_ISCHR(st->st_mode)) {
> if (ioctl(fd, SG_GET_SG_TABLESIZE, &ret) == 0) {
> @@ -1218,44 +1292,27 @@ static int hdev_get_max_segments(int fd, struct stat *st)
> }
> return -ENOTSUP;
> }
> -
> - if (!S_ISBLK(st->st_mode)) {
> - return -ENOTSUP;
> - }
> -
> - sysfspath = g_strdup_printf("/sys/dev/block/%u:%u/queue/max_segments",
> - major(st->st_rdev), minor(st->st_rdev));
> - sysfd = open(sysfspath, O_RDONLY);
> - if (sysfd == -1) {
> - ret = -errno;
> - goto out;
> - }
> - ret = RETRY_ON_EINTR(read(sysfd, buf, sizeof(buf) - 1));
> - if (ret < 0) {
> - ret = -errno;
> - goto out;
> - } else if (ret == 0) {
> - ret = -EIO;
> - goto out;
> - }
> - buf[ret] = 0;
> - /* The file is ended with '\n', pass 'end' to accept that. */
> - ret = qemu_strtol(buf, &end, 10, &max_segments);
> - if (ret == 0 && end && *end == '\n') {
> - ret = max_segments;
> - }
> -
> -out:
> - if (sysfd != -1) {
> - close(sysfd);
> - }
> - g_free(sysfspath);
> - return ret;
> + return get_sysfs_long_val(st, "max_segments");
> #else
> return -ENOTSUP;
> #endif
> }
>
> +static void raw_refresh_zoned_limits(BlockDriverState *bs, struct stat *st,
> + Error **errp)
> +{
> + BlockZoneModel zoned;
> + int ret;
> +
> + bs->bl.zoned = BLK_Z_NONE;
> +
> + ret = get_sysfs_zoned_model(st, &zoned);
> + if (ret < 0 || zoned == BLK_Z_NONE) {
> + return;
> + }
> + bs->bl.zoned = zoned;
> +}
> +
> static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
> {
> BDRVRawState *s = bs->opaque;
> @@ -1297,6 +1354,8 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
> bs->bl.max_hw_iov = ret;
> }
> }
> +
> + raw_refresh_zoned_limits(bs, &st, errp);
> }
>
> static int check_for_dasd(int fd)
