Re: [PATCH v3 1/3] file-posix:add the tracking of the zones write pointers

[Sam Li]

Damien Le Moal <damien.lemoal@opensource.wdc.com> 于2022年10月13日周四 13:13写道：
>
> On 10/10/22 11:33, Sam Li wrote:
> > Since Linux doesn't have a user API to issue zone append operations to
> > zoned devices from user space, the file-posix driver is modified to add
> > zone append emulation using regular writes. To do this, the file-posix
> > driver tracks the wp location of all zones of the device. It uses an
> > array of uint64_t. The most significant bit of each wp location indicates
> > if the zone type is conventional zones.
> >
> > The zones wp can be changed due to the following operations issued:
> > - zone reset: change the wp to the start offset of that zone
> > - zone finish: change to the end location of that zone
> > - write to a zone
> > - zone append
> >
> > Signed-off-by: Sam Li <faithilikerun@gmail.com>
> > ---
> >  block/file-posix.c               | 158 +++++++++++++++++++++++++++++++
> >  include/block/block-common.h     |  14 +++
> >  include/block/block_int-common.h |   5 +
> >  3 files changed, 177 insertions(+)
> >
> > diff --git a/block/file-posix.c b/block/file-posix.c
> > index a9d347292e..17c0b58158 100755
> > --- a/block/file-posix.c
> > +++ b/block/file-posix.c
> > @@ -206,6 +206,7 @@ typedef struct RawPosixAIOData {
> >          struct {
> >              struct iovec *iov;
> >              int niov;
> > +            int64_t *append_sector;
>
> This should be added as part of patch 2. You do not need this to track
> the wp of zones in this patch.
>
> >          } io;
> >          struct {
> >              uint64_t cmd;
> > @@ -226,6 +227,7 @@ typedef struct RawPosixAIOData {
> >          struct {
> >              unsigned long zone_op;
> >              const char *zone_op_name;
> > +            bool all;
> >          } zone_mgmt;
> >      };
> >  } RawPosixAIOData;
> > @@ -1331,6 +1333,67 @@ static int hdev_get_max_segments(int fd, struct stat 
> > *st) {
> >  #endif
> >  }
> >
> > +#if defined(CONFIG_BLKZONED)
> > +static int get_zones_wp(int64_t offset, int fd, BlockZoneWps *wps,
>
> Nit: It would seem more natural to have the fd argument first...
>
> > +                        unsigned int nrz) {
> > +    struct blk_zone *blkz;
> > +    int64_t rep_size;
> > +    int64_t sector = offset >> BDRV_SECTOR_BITS;
> > +    int ret, n = 0, i = 0;
> > +    rep_size = sizeof(struct blk_zone_report) + nrz * sizeof(struct 
> > blk_zone);
> > +    g_autofree struct blk_zone_report *rep = NULL;
> > +
> > +    rep = g_malloc(rep_size);
> > +    blkz = (struct blk_zone *)(rep + 1);
> > +    while (n < nrz) {
> > +        memset(rep, 0, rep_size);
> > +        rep->sector = sector;
> > +        rep->nr_zones = nrz - n;
> > +
> > +        do {
> > +            ret = ioctl(fd, BLKREPORTZONE, rep);
> > +        } while (ret != 0 && errno == EINTR);
> > +        if (ret != 0) {
> > +            error_report("%d: ioctl BLKREPORTZONE at %" PRId64 " failed 
> > %d",
> > +                    fd, offset, errno);
> > +            return -errno;
> > +        }
> > +
> > +        if (!rep->nr_zones) {
> > +            break;
> > +        }
> > +
> > +        for (i = 0; i < rep->nr_zones; i++, n++) {
> > +            /*
> > +             * The wp tracking cares only about sequential writes required 
> > and
> > +             * sequential write preferred zones so that the wp can advance 
> > to
> > +             * the right location.
> > +             * Use the most significant bit of the wp location to indicate 
> > the
> > +             * zone type: 0 for SWR/SWP zones and 1 for conventional zones.
> > +             */
> > +            if (!(blkz[i].type != BLK_ZONE_TYPE_CONVENTIONAL)) {
>
> Double negation... This can simply be:
>
> if (blkz[i].type == BLK_ZONE_TYPE_CONVENTIONAL) {
>
> > +                wps->wp[i] += 1ULL << 63;
>
> No need for the += here. This can be "=".
>
> > +            } else {
> > +                wps->wp[i] = blkz[i].wp << BDRV_SECTOR_BITS;
> > +            }
> > +        }
> > +        sector = blkz[i-1].start + blkz[i-1].len;
>
> spaces missing around the "-" in the "i-1" expressions.
>
> > +    }
> > +
> > +    return 0;
> > +}
> > +
> > +static void update_zones_wp(int64_t offset, int fd, BlockZoneWps *wps,
>
> Same nit as above: fd being the first argument would be a little more
> natural in my opinion.
>
> > +                            unsigned int nrz) {
> > +    qemu_mutex_lock(&wps->lock);
> > +    if (get_zones_wp(offset, fd, wps, nrz) < 0) {
> > +        error_report("report zone wp failed");
> > +        return;
>
> You are leacking the lock here. Remove the return. Also, given that
> get_zones_wp() already prints a message if report fails, I do not think
> the message here is useful.
>
> Also, why is this function void typed ? How can the caller know if the
> update succeeded or not ?

Update failures mean get_zones_wp() fails and that will be reported by
error_report. The error message indicates updates fail not reports
fail. Maybe modifying the message suffices error checking?

+    qemu_mutex_lock(&wps->lock);
+    if (get_zones_wp(offset, fd, wps, nrz) < 0) {
+        error_report("update zone wp failed");
+    }
+    qemu_mutex_unlock(&wps->lock);


>
> > +    }
> > +    qemu_mutex_unlock(&wps->lock);
> > +}
> > +#endif
> > +
> >  static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
> >  {
> >      BDRVRawState *s = bs->opaque;
> > @@ -1414,6 +1477,19 @@ static void raw_refresh_limits(BlockDriverState *bs, 
> > Error **errp)
> >              error_report("Invalid device capacity %" PRId64 " bytes ", 
> > bs->bl.capacity);
> >              return;
> >          }
> > +
> > +        ret = get_sysfs_long_val(&st, "physical_block_size");
> > +        if (ret >= 0) {
> > +            bs->bl.write_granularity = ret;
> > +        }
>
> Why is this change here ? Shouldn't this be part of the previous series
> "Add support for zoned device" ?

Because only zone append uses write_granularity to check the iovector
size alignment. The previous series doesn't use this field.

>
> > +
> > +        bs->bl.wps = g_malloc(sizeof(BlockZoneWps) + sizeof(int64_t) * 
> > ret);
> > +        if (get_zones_wp(0, s->fd, bs->bl.wps, ret) < 0){
> > +            error_report("report wps failed");
> > +            g_free(bs->bl.wps);
> > +            return;
> > +        }
> > +        qemu_mutex_init(&bs->bl.wps->lock);
> >      }
> >  }
> >
> > @@ -1651,6 +1727,20 @@ static int handle_aiocb_rw(void *opaque)
> >      ssize_t nbytes;
> >      char *buf;
> >
> > +    /*
> > +     * The offset of regular writes, append writes is the wp location
> > +     * of that zone.
> > +     */
> > +    if (aiocb->aio_type & QEMU_AIO_WRITE) {
> > +        if (aiocb->bs->bl.zone_size > 0) {
> > +            BlockZoneWps *wps = aiocb->bs->bl.wps;
> > +            qemu_mutex_lock(&wps->lock);
> > +            aiocb->aio_offset = wps->wp[aiocb->aio_offset /
> > +                                        aiocb->bs->bl.zone_size];
> > +            qemu_mutex_unlock(&wps->lock);
> > +        }
>
> I do not understand this hunk at all. What is this trying to do ? zone
> append support goes into patch 2. You are overwritting the user
> specified aio offset using the tracked wp value. That could result in a
> successfull write even if the user sent an unaligned write command. That
> is bad.

Ok, regular writes and append writes got mixed up when I changed the
offset to the wp of that zone.

>
> Here you should only be tracking the write pointer, so increment
> wps->wp[index], which you do below.

Understood. Will move it to the next patch.

>
> > +    }
> > +
> >      if (!(aiocb->aio_type & QEMU_AIO_MISALIGNED)) {
> >          /*
> >           * If there is just a single buffer, and it is properly aligned
> > @@ -1725,6 +1815,24 @@ static int handle_aiocb_rw(void *opaque)
> >
> >  out:
> >      if (nbytes == aiocb->aio_nbytes) {
> > +#if defined(CONFIG_BLKZONED)
> > +        if (aiocb->aio_type & QEMU_AIO_WRITE) {
> > +            BlockZoneWps *wps = aiocb->bs->bl.wps;
> > +            int index = aiocb->aio_offset / aiocb->bs->bl.zone_size;
> > +            if (wps) {
> > +                qemu_mutex_lock(&wps->lock);
> > +                if (!BDRV_ZT_IS_CONV(wps->wp[index])) {
> > +                    uint64_t wend_offset =
> > +                            aiocb->aio_offset + aiocb->aio_nbytes;
> > +                    /* Advance the wp if needed */
> > +                    if (wend_offset > wps->wp[index]){
> > +                        wps->wp[index] = wend_offset;
> > +                    }
> > +                }
> > +                qemu_mutex_unlock(&wps->lock);
> > +            }
> > +        }
> > +#endif
> >          return 0;
> >      } else if (nbytes >= 0 && nbytes < aiocb->aio_nbytes) {
> >          if (aiocb->aio_type & QEMU_AIO_WRITE) {
> > @@ -1736,6 +1844,12 @@ out:
> >          }
> >      } else {
> >          assert(nbytes < 0);
> > +#if defined(CONFIG_BLKZONED)
> > +        if (aiocb->aio_type & QEMU_AIO_WRITE) {
> > +            update_zones_wp(0, aiocb->aio_fildes, aiocb->bs->bl.wps,
> > +                            aiocb->bs->bl.nr_zones);
>
> You only need to update the target zone of the aio, not all zones.
> Updating all zones is actually a bug as wp[] entries for other zones may
> be larger than the device reported wp if there are other write aios in
> flight. So the last argument must be "1" here.

Ok, I understood now.

>
> > +        }
> > +#endif
> >          return nbytes;
> >      }
> >  }
> > @@ -2022,12 +2136,17 @@ static int handle_aiocb_zone_report(void *opaque) {
> >  #if defined(CONFIG_BLKZONED)
> >  static int handle_aiocb_zone_mgmt(void *opaque) {
> >      RawPosixAIOData *aiocb = opaque;
> > +    BlockDriverState *bs = aiocb->bs;
> >      int fd = aiocb->aio_fildes;
> >      int64_t sector = aiocb->aio_offset / 512;
> >      int64_t nr_sectors = aiocb->aio_nbytes / 512;
> > +    uint64_t wend_offset;
> >      struct blk_zone_range range;
> >      int ret;
> >
>
> Why the blank line here ?

For readability, separate it from the execution part.

>
> > +    BlockZoneWps *wps = bs->bl.wps;
> > +    int index = aiocb->aio_offset / bs->bl.zone_size;
> > +
> >      /* Execute the operation */
> >      range.sector = sector;
> >      range.nr_sectors = nr_sectors;
> > @@ -2035,11 +2154,41 @@ static int handle_aiocb_zone_mgmt(void *opaque) {
> >          ret = ioctl(fd, aiocb->zone_mgmt.zone_op, &range);
> >      } while (ret != 0 && errno == EINTR);
> >      if (ret != 0) {
> > +        update_zones_wp(0, aiocb->aio_fildes, aiocb->bs->bl.wps,
> > +                        aiocb->bs->bl.nr_zones);
>
> You need only to update the range of zones that was specified for the
> management option, not all zones. So you must specify the zone
> management aio offset and size/zone_size here.
>
> >          ret = -errno;
> >          error_report("ioctl %s failed %d", aiocb->zone_mgmt.zone_op_name,
> >                       ret);
> >          return ret;
> >      }
> > +
> > +    qemu_mutex_lock(&wps->lock);
> > +    if (!BDRV_ZT_IS_CONV(wps->wp[index])) {
> > +         /*
> > +         * The zoned device allows the last zone smaller that the zone 
> > size.
> > +         */
>
> comment indentation is off.
>
> > +        if (aiocb->aio_nbytes < bs->bl.zone_size) {
> > +            wend_offset = aiocb->aio_offset + aiocb->aio_nbytes;
> > +        } else {
> > +            wend_offset = aiocb->aio_offset + bs->bl.zone_size;
> > +        }
> > +
> > +        if (aiocb->aio_offset != wps->wp[index] &&
> > +            aiocb->zone_mgmt.zone_op == BLKRESETZONE) {
>
> I do not understand the condition here. Why do you have
> "aiocb->aio_offset != wps->wp[index]" ?

It is intended for zone state checks. aio_offset (= start byte of that
zone) = wp means this zone is empty. Only non-empty zones will be
reset.

>
> > +            if (aiocb->zone_mgmt.all) {
>
> This is the only place where you use this all boolean field. For
> simplicity, I would drop this field completely and test that
> aiocb->aio_offset == 0 && aiocb->aio_nbytes == bs->bl.capacity to detect
> a reset all zones operation.

Right, the capacity field makes it possible. I'll drop it.

>
> > +                for (int i = 0; i < bs->bl.nr_zones; ++i) {
> > +                    wps->wp[i] = i * bs->bl.zone_size;
>
> You are not handling conventional zones here. For conventional zones,
> you should not change the value. Otherwise, BDRV_ZT_IS_CONV() will
> always return false after this.

Right, will add a condition line here:
+ if (! BDRV_ZT_IS_CONV(wps->wp[i]))

>
> > +                }
> > +            } else {
> > +                wps->wp[index] = aiocb->aio_offset;
> > +            }
> > +        } else if (aiocb->aio_offset != wps->wp[index] &&
> > +            aiocb->zone_mgmt.zone_op == BLKFINISHZONE) {
>
> Same comment here. Why do you have "aiocb->aio_offset != wps->wp[index]" ?

This should be wend_offset != wps->wp[index]. It means if this zone is
full, no need to finish it.

>
> > +            wps->wp[index] = wend_offset;
> > +        }
> > +    }
> > +    qemu_mutex_unlock(&wps->lock);
> > +
> >      return ret;
> >  }
> >  #endif
> > @@ -2480,6 +2629,12 @@ static void raw_close(BlockDriverState *bs)
> >      BDRVRawState *s = bs->opaque;
> >
> >      if (s->fd >= 0) {
> > +#if defined(CONFIG_BLKZONED)
> > +        if (bs->bl.wps) {
> > +            qemu_mutex_destroy(&bs->bl.wps->lock);
> > +            g_free(bs->bl.wps);
> > +        }
> > +#endif
> >          qemu_close(s->fd);
> >          s->fd = -1;
> >      }
> > @@ -3278,6 +3433,7 @@ static int coroutine_fn 
> > raw_co_zone_mgmt(BlockDriverState *bs, BlockZoneOp op,
> >      int64_t zone_size, zone_size_mask;
> >      const char *zone_op_name;
> >      unsigned long zone_op;
> > +    bool is_all = false;
> >
> >      zone_size = bs->bl.zone_size;
> >      zone_size_mask = zone_size - 1;
> > @@ -3314,6 +3470,7 @@ static int coroutine_fn 
> > raw_co_zone_mgmt(BlockDriverState *bs, BlockZoneOp op,
> >      case BLK_ZO_RESET_ALL:
> >          zone_op_name = "BLKRESETZONE";
> >          zone_op = BLKRESETZONE;
> > +        is_all = true;
> >          break;
> >      default:
> >          g_assert_not_reached();
> > @@ -3328,6 +3485,7 @@ static int coroutine_fn 
> > raw_co_zone_mgmt(BlockDriverState *bs, BlockZoneOp op,
> >          .zone_mgmt  = {
> >              .zone_op = zone_op,
> >              .zone_op_name = zone_op_name,
> > +            .all = is_all,
> >          },
> >      };
> >
> > diff --git a/include/block/block-common.h b/include/block/block-common.h
> > index 882de6825e..b8b2dba64a 100644
> > --- a/include/block/block-common.h
> > +++ b/include/block/block-common.h
> > @@ -93,6 +93,14 @@ typedef struct BlockZoneDescriptor {
> >      BlockZoneCondition cond;
> >  } BlockZoneDescriptor;
> >
> > +/*
> > + * Track write pointers of a zone in bytes.
> > + */
> > +typedef struct BlockZoneWps {
> > +    QemuMutex lock;
> > +    uint64_t wp[];
> > +} BlockZoneWps;
> > +
> >  typedef struct BlockDriverInfo {
> >      /* in bytes, 0 if irrelevant */
> >      int cluster_size;
> > @@ -206,6 +214,12 @@ typedef enum {
> >  #define BDRV_SECTOR_BITS   9
> >  #define BDRV_SECTOR_SIZE   (1ULL << BDRV_SECTOR_BITS)
> >
> > +/*
> > + * Get the first most significant bit of wp. If it is zero, then
> > + * the zone type is SWR.
> > + */
> > +#define BDRV_ZT_IS_CONV(wp)    (wp & (1ULL << 63))
> > +
> >  #define BDRV_REQUEST_MAX_SECTORS MIN_CONST(SIZE_MAX >> BDRV_SECTOR_BITS, \
> >                                             INT_MAX >> BDRV_SECTOR_BITS)
> >  #define BDRV_REQUEST_MAX_BYTES (BDRV_REQUEST_MAX_SECTORS << 
> > BDRV_SECTOR_BITS)
> > diff --git a/include/block/block_int-common.h 
> > b/include/block/block_int-common.h
> > index 37dddc603c..59c2d1316d 100644
> > --- a/include/block/block_int-common.h
> > +++ b/include/block/block_int-common.h
> > @@ -857,6 +857,11 @@ typedef struct BlockLimits {
> >
> >      /* device capacity expressed in bytes */
> >      int64_t capacity;
> > +
> > +    /* array of write pointers' location of each zone in the zoned device. 
> > */
> > +    BlockZoneWps *wps;
> > +
> > +    int64_t write_granularity;
> >  } BlockLimits;
> >
> >  typedef struct BdrvOpBlocker BdrvOpBlocker;
>
> --
> Damien Le Moal
> Western Digital Research
>