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authorBart Van Assche <bart.vanassche@wdc.com>2018-04-17 04:04:41 +0300
committerMartin K. Petersen <martin.petersen@oracle.com>2018-04-19 07:04:10 +0300
commitccce20fc7968d546fb1e8e147bf5cdc8afc4278a (patch)
tree03eb832a953db5bfb9801adb4e6a08a25494c6b1 /include/linux/blkdev.h
parent505aa4b6a8834a2300971c5220c380c3271ebde3 (diff)
downloadlinux-ccce20fc7968d546fb1e8e147bf5cdc8afc4278a.tar.xz
scsi: sd_zbc: Avoid that resetting a zone fails sporadically
Since SCSI scanning occurs asynchronously, since sd_revalidate_disk() is called from sd_probe_async() and since sd_revalidate_disk() calls sd_zbc_read_zones() it can happen that sd_zbc_read_zones() is called concurrently with blkdev_report_zones() and/or blkdev_reset_zones(). That can cause these functions to fail with -EIO because sd_zbc_read_zones() e.g. sets q->nr_zones to zero before restoring it to the actual value, even if no drive characteristics have changed. Avoid that this can happen by making the following changes: - Protect the code that updates zone information with blk_queue_enter() and blk_queue_exit(). - Modify sd_zbc_setup_seq_zones_bitmap() and sd_zbc_setup() such that these functions do not modify struct scsi_disk before all zone information has been obtained. Note: since commit 055f6e18e08f ("block: Make q_usage_counter also track legacy requests"; kernel v4.15) the request queue freezing mechanism also affects legacy request queues. Fixes: 89d947561077 ("sd: Implement support for ZBC devices") Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Damien Le Moal <damien.lemoal@wdc.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Hannes Reinecke <hare@suse.com> Cc: stable@vger.kernel.org # v4.16 Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'include/linux/blkdev.h')
-rw-r--r--include/linux/blkdev.h5
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 9af3e0f430bc..21e21f273a21 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -605,6 +605,11 @@ struct request_queue {
* initialized by the low level device driver (e.g. scsi/sd.c).
* Stacking drivers (device mappers) may or may not initialize
* these fields.
+ *
+ * Reads of this information must be protected with blk_queue_enter() /
+ * blk_queue_exit(). Modifying this information is only allowed while
+ * no requests are being processed. See also blk_mq_freeze_queue() and
+ * blk_mq_unfreeze_queue().
*/
unsigned int nr_zones;
unsigned long *seq_zones_bitmap;