On 07/23/16 13:31, Hannes Reinecke wrote:
On 07/22/2016 11:56 PM, Ewan D. Milne wrote:
On Tue, 2016-07-19 at 15:25 +0200, Hannes Reinecke wrote:
For ZBC devices I/O must not cross zone boundaries, so setup
the 'chunk_sectors' block queue setting to the zone size.
This is only valid for REPORT ZONES SAME type 2 or 3;
for other types the zone sizes might be different
for individual zones. So issue a warning if the type is
found to be different.
Also the capacity might be different from the announced
capacity, so adjust it as needed.
Signed-off-by: Hannes Reinecke <hare@xxxxxxxx>
...
+static void sd_read_zones(struct scsi_disk *sdkp, unsigned char *buffer)
+{
+ int retval;
+ unsigned char *desc;
+ u32 rep_len;
+ u8 same;
+ u64 zone_len, lba;
+
+ if (sdkp->zoned != 1)
+ /* Device managed, no special handling required */
+ return;
+
+ retval = sd_zbc_report_zones(sdkp, buffer, SD_BUF_SIZE,
+ 0, ZBC_ZONE_REPORTING_OPTION_ALL, false);
+ if (retval < 0)
+ return;
+
+ rep_len = get_unaligned_be32(&buffer[0]);
+ if (rep_len < 64) {
+ sd_printk(KERN_WARNING, sdkp,
+ "REPORT ZONES report invalid length %u\n",
+ rep_len);
+ return;
+ }
+
+ if (sdkp->rc_basis == 0) {
+ /* The max_lba field is the capacity of a zoned device */
+ lba = get_unaligned_be64(&buffer[8]);
+ if (lba + 1 > sdkp->capacity) {
+ sd_printk(KERN_WARNING, sdkp,
+ "Max LBA %zu (capacity %zu)\n",
+ (sector_t) lba + 1, sdkp->capacity);
+ sdkp->capacity = lba + 1;
+ }
+ }
+
+ /*
+ * Adjust 'chunk_sectors' to the zone length if the device
+ * supports equal zone sizes.
+ */
+ same = buffer[4] & 0xf;
+ if (same == 0 || same > 3) {
+ sd_printk(KERN_WARNING, sdkp,
+ "REPORT ZONES SAME type %d not supported\n", same);
+ return;
+ }
+ /* Read the zone length from the first zone descriptor */
+ desc = &buffer[64];
+ zone_len = logical_to_sectors(sdkp->device,
+ get_unaligned_be64(&desc[8]));
+ blk_queue_chunk_sectors(sdkp->disk->queue, zone_len);
+}
+
So, blk_queue_chunk_sectors() has:
void blk_queue_chunk_sectors(struct request_queue *q, unsigned int chunk_sectors)
{
BUG_ON(!is_power_of_2(chunk_sectors));
q->limits.chunk_sectors = chunk_sectors;
}
and it seems like if some device reports a non-power-of-2 zone_len then we
will BUG_ON(). Probably would be better if we reported an error instead?
The ZBC spec mandates that the zone size must be a power of 2.
So I don't have problems with triggering a BUG_ON for non-compliant
drives.
Triggering BUG_ON() if zone_len is not a power of two is completely
unacceptable. No matter what zone information a ZBC drive exports that
shouldn't result in a kernel oops.
Bart.
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