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>

2 files changed, 87 insertions, 58 deletions

diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c
index 41df75eea57b..210407cd2341 100644
--- a/drivers/scsi/sd_zbc.c
+++ b/drivers/scsi/sd_zbc.c
@@ -400,8 +400,10 @@ static int sd_zbc_check_capacity(struct scsi_disk *sdkp, unsigned char *buf)
  *
  * Check that all zones of the device are equal. The last zone can however
  * be smaller. The zone size must also be a power of two number of LBAs.
+ *
+ * Returns the zone size in bytes upon success or an error code upon failure.
  */
-static int sd_zbc_check_zone_size(struct scsi_disk *sdkp)
+static s64 sd_zbc_check_zone_size(struct scsi_disk *sdkp)
 {
         u64 zone_blocks = 0;
         sector_t block = 0;
@@ -412,8 +414,6 @@ static int sd_zbc_check_zone_size(struct scsi_disk *sdkp)
         int ret;
         u8 same;
 
-        sdkp->zone_blocks = 0;
-
         /* Get a buffer */
         buf = kmalloc(SD_ZBC_BUF_SIZE, GFP_KERNEL);
         if (!buf)
@@ -445,16 +445,17 @@ static int sd_zbc_check_zone_size(struct scsi_disk *sdkp)
 
                 /* Parse zone descriptors */
                 while (rec < buf + buf_len) {
-                        zone_blocks = get_unaligned_be64(&rec[8]);
-                        if (sdkp->zone_blocks == 0) {
-                                sdkp->zone_blocks = zone_blocks;
-                        } else if (zone_blocks != sdkp->zone_blocks &&
-                                   (block + zone_blocks < sdkp->capacity
-                                    || zone_blocks > sdkp->zone_blocks)) {
-                                zone_blocks = 0;
+                        u64 this_zone_blocks = get_unaligned_be64(&rec[8]);
+
+                        if (zone_blocks == 0) {
+                                zone_blocks = this_zone_blocks;
+                        } else if (this_zone_blocks != zone_blocks &&
+                                   (block + this_zone_blocks < sdkp->capacity
+                                    || this_zone_blocks > zone_blocks)) {
+                                this_zone_blocks = 0;
                                 goto out;
                         }
-                        block += zone_blocks;
+                        block += this_zone_blocks;
                         rec += 64;
                 }
 
@@ -467,8 +468,6 @@ static int sd_zbc_check_zone_size(struct scsi_disk *sdkp)
 
         } while (block < sdkp->capacity);
 
-        zone_blocks = sdkp->zone_blocks;
-
 out:
         if (!zone_blocks) {
                 if (sdkp->first_scan)
@@ -488,8 +487,7 @@ out:
                                   "Zone size too large\n");
                 ret = -ENODEV;
         } else {
-                sdkp->zone_blocks = zone_blocks;
-                sdkp->zone_shift = ilog2(zone_blocks);
+                ret = zone_blocks;
         }
 
 out_free:
@@ -500,15 +498,14 @@ out_free:
 
 /**
  * sd_zbc_alloc_zone_bitmap - Allocate a zone bitmap (one bit per zone).
- * @sdkp: The disk of the bitmap
+ * @nr_zones: Number of zones to allocate space for.
+ * @numa_node: NUMA node to allocate the memory from.
  */
-static inline unsigned long *sd_zbc_alloc_zone_bitmap(struct scsi_disk *sdkp)
+static inline unsigned long *
+sd_zbc_alloc_zone_bitmap(u32 nr_zones, int numa_node)
 {
-        struct request_queue *q = sdkp->disk->queue;
-
-        return kzalloc_node(BITS_TO_LONGS(sdkp->nr_zones)
-                            * sizeof(unsigned long),
-                            GFP_KERNEL, q->node);
+        return kzalloc_node(BITS_TO_LONGS(nr_zones) * sizeof(unsigned long),
+                            GFP_KERNEL, numa_node);
 }
 
 /**
@@ -516,6 +513,7 @@ static inline unsigned long *sd_zbc_alloc_zone_bitmap(struct scsi_disk *sdkp)
  * @sdkp: disk used
  * @buf: report reply buffer
  * @buflen: length of @buf
+ * @zone_shift: logarithm base 2 of the number of blocks in a zone
  * @seq_zones_bitmap: bitmap of sequential zones to set
  *
  * Parse reported zone descriptors in @buf to identify sequential zones and
@@ -525,7 +523,7 @@ static inline unsigned long *sd_zbc_alloc_zone_bitmap(struct scsi_disk *sdkp)
  * Return the LBA after the last zone reported.
  */
 static sector_t sd_zbc_get_seq_zones(struct scsi_disk *sdkp, unsigned char *buf,
-                                     unsigned int buflen,
+                                     unsigned int buflen, u32 zone_shift,
                                      unsigned long *seq_zones_bitmap)
 {
         sector_t lba, next_lba = sdkp->capacity;
@@ -544,7 +542,7 @@ static sector_t sd_zbc_get_seq_zones(struct scsi_disk *sdkp, unsigned char *buf,
                 if (type != ZBC_ZONE_TYPE_CONV &&
                     cond != ZBC_ZONE_COND_READONLY &&
                     cond != ZBC_ZONE_COND_OFFLINE)
-                        set_bit(lba >> sdkp->zone_shift, seq_zones_bitmap);
+                        set_bit(lba >> zone_shift, seq_zones_bitmap);
                 next_lba = lba + get_unaligned_be64(&rec[8]);
                 rec += 64;
         }
@@ -553,12 +551,16 @@ static sector_t sd_zbc_get_seq_zones(struct scsi_disk *sdkp, unsigned char *buf,
 }
 
 /**
- * sd_zbc_setup_seq_zones_bitmap - Initialize the disk seq zone bitmap.
+ * sd_zbc_setup_seq_zones_bitmap - Initialize a seq zone bitmap.
  * @sdkp: target disk
+ * @zone_shift: logarithm base 2 of the number of blocks in a zone
+ * @nr_zones: number of zones to set up a seq zone bitmap for
  *
  * Allocate a zone bitmap and initialize it by identifying sequential zones.
  */
-static int sd_zbc_setup_seq_zones_bitmap(struct scsi_disk *sdkp)
+static unsigned long *
+sd_zbc_setup_seq_zones_bitmap(struct scsi_disk *sdkp, u32 zone_shift,
+                              u32 nr_zones)
 {
         struct request_queue *q = sdkp->disk->queue;
         unsigned long *seq_zones_bitmap;
@@ -566,9 +568,9 @@ static int sd_zbc_setup_seq_zones_bitmap(struct scsi_disk *sdkp)
         unsigned char *buf;
         int ret = -ENOMEM;
 
-        seq_zones_bitmap = sd_zbc_alloc_zone_bitmap(sdkp);
+        seq_zones_bitmap = sd_zbc_alloc_zone_bitmap(nr_zones, q->node);
         if (!seq_zones_bitmap)
-                return -ENOMEM;
+                return ERR_PTR(-ENOMEM);
 
         buf = kmalloc(SD_ZBC_BUF_SIZE, GFP_KERNEL);
         if (!buf)
@@ -579,7 +581,7 @@ static int sd_zbc_setup_seq_zones_bitmap(struct scsi_disk *sdkp)
                 if (ret)
                         goto out;
                 lba = sd_zbc_get_seq_zones(sdkp, buf, SD_ZBC_BUF_SIZE,
-                                           seq_zones_bitmap);
+                                           zone_shift, seq_zones_bitmap);
         }
 
         if (lba != sdkp->capacity) {
@@ -591,12 +593,9 @@ out:
         kfree(buf);
         if (ret) {
                 kfree(seq_zones_bitmap);
-                return ret;
+                return ERR_PTR(ret);
         }
-
-        q->seq_zones_bitmap = seq_zones_bitmap;
-
-        return 0;
+        return seq_zones_bitmap;
 }
 
 static void sd_zbc_cleanup(struct scsi_disk *sdkp)
@@ -612,44 +611,64 @@ static void sd_zbc_cleanup(struct scsi_disk *sdkp)
         q->nr_zones = 0;
 }
 
-static int sd_zbc_setup(struct scsi_disk *sdkp)
+static int sd_zbc_setup(struct scsi_disk *sdkp, u32 zone_blocks)
 {
         struct request_queue *q = sdkp->disk->queue;
+        u32 zone_shift = ilog2(zone_blocks);
+        u32 nr_zones;
         int ret;
 
-        /* READ16/WRITE16 is mandatory for ZBC disks */
-        sdkp->device->use_16_for_rw = 1;
-        sdkp->device->use_10_for_rw = 0;
-
         /* chunk_sectors indicates the zone size */
-        blk_queue_chunk_sectors(sdkp->disk->queue,
-                        logical_to_sectors(sdkp->device, sdkp->zone_blocks));
-        sdkp->nr_zones =
-                round_up(sdkp->capacity, sdkp->zone_blocks) >> sdkp->zone_shift;
+        blk_queue_chunk_sectors(q,
+                        logical_to_sectors(sdkp->device, zone_blocks));
+        nr_zones = round_up(sdkp->capacity, zone_blocks) >> zone_shift;
 
         /*
          * Initialize the device request queue information if the number
          * of zones changed.
          */
-        if (sdkp->nr_zones != q->nr_zones) {
-
-                sd_zbc_cleanup(sdkp);
-
-                q->nr_zones = sdkp->nr_zones;
-                if (sdkp->nr_zones) {
-                        q->seq_zones_wlock = sd_zbc_alloc_zone_bitmap(sdkp);
-                        if (!q->seq_zones_wlock) {
+        if (nr_zones != sdkp->nr_zones || nr_zones != q->nr_zones) {
+                unsigned long *seq_zones_wlock = NULL, *seq_zones_bitmap = NULL;
+                size_t zone_bitmap_size;
+
+                if (nr_zones) {
+                        seq_zones_wlock = sd_zbc_alloc_zone_bitmap(nr_zones,
+                                                                   q->node);
+                        if (!seq_zones_wlock) {
                                 ret = -ENOMEM;
                                 goto err;
                         }
 
-                        ret = sd_zbc_setup_seq_zones_bitmap(sdkp);
-                        if (ret) {
-                                sd_zbc_cleanup(sdkp);
+                        seq_zones_bitmap = sd_zbc_setup_seq_zones_bitmap(sdkp,
+                                                        zone_shift, nr_zones);
+                        if (IS_ERR(seq_zones_bitmap)) {
+                                ret = PTR_ERR(seq_zones_bitmap);
+                                kfree(seq_zones_wlock);
                                 goto err;
                         }
                 }
-
+                zone_bitmap_size = BITS_TO_LONGS(nr_zones) *
+                        sizeof(unsigned long);
+                blk_mq_freeze_queue(q);
+                if (q->nr_zones != nr_zones) {
+                        /* READ16/WRITE16 is mandatory for ZBC disks */
+                        sdkp->device->use_16_for_rw = 1;
+                        sdkp->device->use_10_for_rw = 0;
+
+                        sdkp->zone_blocks = zone_blocks;
+                        sdkp->zone_shift = zone_shift;
+                        sdkp->nr_zones = nr_zones;
+                        q->nr_zones = nr_zones;
+                        swap(q->seq_zones_wlock, seq_zones_wlock);
+                        swap(q->seq_zones_bitmap, seq_zones_bitmap);
+                } else if (memcmp(q->seq_zones_bitmap, seq_zones_bitmap,
+                                  zone_bitmap_size) != 0) {
+                        memcpy(q->seq_zones_bitmap, seq_zones_bitmap,
+                               zone_bitmap_size);
+                }
+                blk_mq_unfreeze_queue(q);
+                kfree(seq_zones_wlock);
+                kfree(seq_zones_bitmap);
         }
 
         return 0;
@@ -661,6 +680,7 @@ err:
 
 int sd_zbc_read_zones(struct scsi_disk *sdkp, unsigned char *buf)
 {
+        int64_t zone_blocks;
         int ret;
 
         if (!sd_is_zoned(sdkp))
@@ -697,12 +717,16 @@ int sd_zbc_read_zones(struct scsi_disk *sdkp, unsigned char *buf)
          * Check zone size: only devices with a constant zone size (except
          * an eventual last runt zone) that is a power of 2 are supported.
          */
-        ret = sd_zbc_check_zone_size(sdkp);
-        if (ret)
+        zone_blocks = sd_zbc_check_zone_size(sdkp);
+        ret = -EFBIG;
+        if (zone_blocks != (u32)zone_blocks)
+                goto err;
+        ret = zone_blocks;
+        if (ret < 0)
                 goto err;
 
         /* The drive satisfies the kernel restrictions: set it up */
-        ret = sd_zbc_setup(sdkp);
+        ret = sd_zbc_setup(sdkp, zone_blocks);
         if (ret)
                 goto err;
 
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;