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Tue, 26 Apr 2022 19:45:35 -0700 (PDT) Received: from [10.225.163.27] (unknown [10.225.163.27]) by usg-ed-osssrv.wdc.com (Postfix) with ESMTPSA id 4Kp35M67Knz1Rvlc; Tue, 26 Apr 2022 19:45:27 -0700 (PDT) Message-ID: <7d1fdd1e-c854-4744-8bec-7d222fb9be76@opensource.wdc.com> Date: Wed, 27 Apr 2022 11:45:26 +0900 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH v4 02/10] block: Add copy offload support infrastructure Content-Language: en-US To: Nitesh Shetty Cc: chaitanyak@nvidia.com, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, dm-devel@redhat.com, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org, axboe@kernel.dk, msnitzer@redhat.com, bvanassche@acm.org, martin.petersen@oracle.com, hare@suse.de, kbusch@kernel.org, hch@lst.de, Frederick.Knight@netapp.com, osandov@fb.com, lsf-pc@lists.linux-foundation.org, djwong@kernel.org, josef@toxicpanda.com, clm@fb.com, dsterba@suse.com, tytso@mit.edu, jack@suse.com, nitheshshetty@gmail.com, gost.dev@samsung.com, Arnav Dawn , Alasdair Kergon , Mike Snitzer , Sagi Grimberg , James Smart , Chaitanya Kulkarni , Naohiro Aota , Johannes Thumshirn , Alexander Viro , linux-kernel@vger.kernel.org References: <20220426101241.30100-1-nj.shetty@samsung.com> <20220426101241.30100-3-nj.shetty@samsung.com> From: Damien Le Moal Organization: Western Digital Research In-Reply-To: <20220426101241.30100-3-nj.shetty@samsung.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-6.3 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,RCVD_IN_DNSWL_MED, SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/26/22 19:12, Nitesh Shetty wrote: > Introduce blkdev_issue_copy which supports source and destination bdevs, > and an array of (source, destination and copy length) tuples. > Introduce REQ_COPY copy offload operation flag. Create a read-write > bio pair with a token as payload and submitted to the device in order. > Read request populates token with source specific information which > is then passed with write request. > This design is courtesy Mikulas Patocka's token based copy > > Larger copy will be divided, based on max_copy_sectors, > max_copy_range_sector limits. > > Signed-off-by: Nitesh Shetty > Signed-off-by: Arnav Dawn > --- > block/blk-lib.c | 232 ++++++++++++++++++++++++++++++++++++++ > block/blk.h | 2 + > include/linux/blk_types.h | 21 ++++ > include/linux/blkdev.h | 2 + > include/uapi/linux/fs.h | 14 +++ > 5 files changed, 271 insertions(+) > > diff --git a/block/blk-lib.c b/block/blk-lib.c > index 09b7e1200c0f..ba9da2d2f429 100644 > --- a/block/blk-lib.c > +++ b/block/blk-lib.c > @@ -117,6 +117,238 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, > } > EXPORT_SYMBOL(blkdev_issue_discard); > > +/* > + * Wait on and process all in-flight BIOs. This must only be called once > + * all bios have been issued so that the refcount can only decrease. > + * This just waits for all bios to make it through bio_copy_end_io. IO > + * errors are propagated through cio->io_error. > + */ > +static int cio_await_completion(struct cio *cio) > +{ > + int ret = 0; > + unsigned long flags; > + > + spin_lock_irqsave(&cio->lock, flags); > + if (cio->refcount) { > + cio->waiter = current; > + __set_current_state(TASK_UNINTERRUPTIBLE); > + spin_unlock_irqrestore(&cio->lock, flags); > + blk_io_schedule(); > + /* wake up sets us TASK_RUNNING */ > + spin_lock_irqsave(&cio->lock, flags); > + cio->waiter = NULL; > + ret = cio->io_err; > + } > + spin_unlock_irqrestore(&cio->lock, flags); > + kvfree(cio); cio is allocated with kzalloc() == kmalloc(). So why the kvfree() here ? > + > + return ret; > +} > + > +static void bio_copy_end_io(struct bio *bio) > +{ > + struct copy_ctx *ctx = bio->bi_private; > + struct cio *cio = ctx->cio; > + sector_t clen; > + int ri = ctx->range_idx; > + unsigned long flags; > + bool wake = false; > + > + if (bio->bi_status) { > + cio->io_err = bio->bi_status; > + clen = (bio->bi_iter.bi_sector << SECTOR_SHIFT) - ctx->start_sec; > + cio->rlist[ri].comp_len = min_t(sector_t, clen, cio->rlist[ri].comp_len); long line. > + } > + __free_page(bio->bi_io_vec[0].bv_page); > + kfree(ctx); > + bio_put(bio); > + > + spin_lock_irqsave(&cio->lock, flags); > + if (((--cio->refcount) <= 0) && cio->waiter) > + wake = true; > + spin_unlock_irqrestore(&cio->lock, flags); > + if (wake) > + wake_up_process(cio->waiter); > +} > + > +/* > + * blk_copy_offload - Use device's native copy offload feature > + * Go through user provide payload, prepare new payload based on device's copy offload limits. long line. > + */ > +int blk_copy_offload(struct block_device *src_bdev, int nr_srcs, > + struct range_entry *rlist, struct block_device *dst_bdev, gfp_t gfp_mask) long line. rlist is an array, but rlist naming implies a list. Why not call that argument "ranges" ? The argument ordering is also strange. I would make that: blk_copy_offload(struct block_device *src_bdev, struct block_device *dst_bdev, struct range_entry *rlist, int nr_srcs, gfp_t gfp_mask) > +{ > + struct request_queue *sq = bdev_get_queue(src_bdev); > + struct request_queue *dq = bdev_get_queue(dst_bdev); > + struct bio *read_bio, *write_bio; > + struct copy_ctx *ctx; > + struct cio *cio; > + struct page *token; > + sector_t src_blk, copy_len, dst_blk; > + sector_t remaining, max_copy_len = LONG_MAX; > + unsigned long flags; > + int ri = 0, ret = 0; > + > + cio = kzalloc(sizeof(struct cio), GFP_KERNEL); > + if (!cio) > + return -ENOMEM; > + cio->rlist = rlist; > + spin_lock_init(&cio->lock); > + > + max_copy_len = min_t(sector_t, sq->limits.max_copy_sectors, dq->limits.max_copy_sectors); > + max_copy_len = min3(max_copy_len, (sector_t)sq->limits.max_copy_range_sectors, > + (sector_t)dq->limits.max_copy_range_sectors) << SECTOR_SHIFT; But max_copy_range_sectors is for one sector only, right ? So what is this second min3() doing ? It is mixing up total length and one range length. The device should not have reported a per range max length larger than the total length in the first place, right ? If it does, that would be a very starnge device... > + > + for (ri = 0; ri < nr_srcs; ri++) { > + cio->rlist[ri].comp_len = rlist[ri].len; > + src_blk = rlist[ri].src; > + dst_blk = rlist[ri].dst; > + for (remaining = rlist[ri].len; remaining > 0; remaining -= copy_len) { > + copy_len = min(remaining, max_copy_len); > + > + token = alloc_page(gfp_mask); > + if (unlikely(!token)) { > + ret = -ENOMEM; > + goto err_token; > + } > + > + ctx = kzalloc(sizeof(struct copy_ctx), gfp_mask); > + if (!ctx) { > + ret = -ENOMEM; > + goto err_ctx; > + } > + ctx->cio = cio; > + ctx->range_idx = ri; > + ctx->start_sec = dst_blk; > + > + read_bio = bio_alloc(src_bdev, 1, REQ_OP_READ | REQ_COPY | REQ_NOMERGE, > + gfp_mask); > + if (!read_bio) { > + ret = -ENOMEM; > + goto err_read_bio; > + } > + read_bio->bi_iter.bi_sector = src_blk >> SECTOR_SHIFT; > + __bio_add_page(read_bio, token, PAGE_SIZE, 0); > + /*__bio_add_page increases bi_size by len, so overwrite it with copy len*/ > + read_bio->bi_iter.bi_size = copy_len; > + ret = submit_bio_wait(read_bio); > + bio_put(read_bio); > + if (ret) > + goto err_read_bio; > + > + write_bio = bio_alloc(dst_bdev, 1, REQ_OP_WRITE | REQ_COPY | REQ_NOMERGE, > + gfp_mask); > + if (!write_bio) { > + ret = -ENOMEM; > + goto err_read_bio; > + } > + write_bio->bi_iter.bi_sector = dst_blk >> SECTOR_SHIFT; > + __bio_add_page(write_bio, token, PAGE_SIZE, 0); > + /*__bio_add_page increases bi_size by len, so overwrite it with copy len*/ > + write_bio->bi_iter.bi_size = copy_len; > + write_bio->bi_end_io = bio_copy_end_io; > + write_bio->bi_private = ctx; > + > + spin_lock_irqsave(&cio->lock, flags); > + ++cio->refcount; Shouldn't this be an atomic_t ? And wrap lines please. Many are too long. > + spin_unlock_irqrestore(&cio->lock, flags); > + > + submit_bio(write_bio); > + src_blk += copy_len; > + dst_blk += copy_len; > + } > + } > + > + /* Wait for completion of all IO's*/ > + return cio_await_completion(cio); > + > +err_read_bio: > + kfree(ctx); > +err_ctx: > + __free_page(token); > +err_token: > + rlist[ri].comp_len = min_t(sector_t, rlist[ri].comp_len, (rlist[ri].len - remaining)); > + > + cio->io_err = ret; > + return cio_await_completion(cio); > +} > + > +static inline int blk_copy_sanity_check(struct block_device *src_bdev, > + struct block_device *dst_bdev, struct range_entry *rlist, int nr) > +{ > + unsigned int align_mask = max( > + bdev_logical_block_size(dst_bdev), bdev_logical_block_size(src_bdev)) - 1; > + sector_t len = 0; > + int i; > + > + for (i = 0; i < nr; i++) { > + if (rlist[i].len) > + len += rlist[i].len; > + else > + return -EINVAL; Reverse the if condition and return to avoid the else. > + if ((rlist[i].dst & align_mask) || (rlist[i].src & align_mask) || > + (rlist[i].len & align_mask)) > + return -EINVAL; > + rlist[i].comp_len = 0; > + } > + > + if (len && len >= MAX_COPY_TOTAL_LENGTH) > + return -EINVAL; > + > + return 0; > +} > + > +static inline bool blk_check_copy_offload(struct request_queue *src_q, > + struct request_queue *dest_q) > +{ > + if (blk_queue_copy(dest_q) && blk_queue_copy(src_q)) > + return true; > + > + return false; return blk_queue_copy(dest_q) && blk_queue_copy(src_q); would be simpler. > +} > + > +/* > + * blkdev_issue_copy - queue a copy > + * @src_bdev: source block device > + * @nr_srcs: number of source ranges to copy > + * @rlist: array of source/dest/len > + * @dest_bdev: destination block device > + * @gfp_mask: memory allocation flags (for bio_alloc) > + * > + * Description: > + * Copy source ranges from source block device to destination block device. > + * length of a source range cannot be zero. > + */ > +int blkdev_issue_copy(struct block_device *src_bdev, int nr, > + struct range_entry *rlist, struct block_device *dest_bdev, gfp_t gfp_mask) same comment as above about args order and naming. > +{ > + struct request_queue *src_q = bdev_get_queue(src_bdev); > + struct request_queue *dest_q = bdev_get_queue(dest_bdev); > + int ret = -EINVAL; > + > + if (!src_q || !dest_q) > + return -ENXIO; > + > + if (!nr) > + return -EINVAL; > + > + if (nr >= MAX_COPY_NR_RANGE) > + return -EINVAL; Where do you check the number of ranges against what the device can do ? > + > + if (bdev_read_only(dest_bdev)) > + return -EPERM; > + > + ret = blk_copy_sanity_check(src_bdev, dest_bdev, rlist, nr); > + if (ret) > + return ret; nr check should be in this function... > + > + if (blk_check_copy_offload(src_q, dest_q)) ...which should be only one function with this one. > + ret = blk_copy_offload(src_bdev, nr, rlist, dest_bdev, gfp_mask); > + > + return ret; > +} > +EXPORT_SYMBOL_GPL(blkdev_issue_copy); > + > static int __blkdev_issue_write_zeroes(struct block_device *bdev, > sector_t sector, sector_t nr_sects, gfp_t gfp_mask, > struct bio **biop, unsigned flags) > diff --git a/block/blk.h b/block/blk.h > index 434017701403..6010eda58c70 100644 > --- a/block/blk.h > +++ b/block/blk.h > @@ -291,6 +291,8 @@ static inline bool blk_may_split(struct request_queue *q, struct bio *bio) > break; > } > > + if (unlikely(op_is_copy(bio->bi_opf))) > + return false; > /* > * All drivers must accept single-segments bios that are <= PAGE_SIZE. > * This is a quick and dirty check that relies on the fact that > diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h > index c62274466e72..f5b01f284c43 100644 > --- a/include/linux/blk_types.h > +++ b/include/linux/blk_types.h > @@ -418,6 +418,7 @@ enum req_flag_bits { > /* for driver use */ > __REQ_DRV, > __REQ_SWAP, /* swapping request. */ > + __REQ_COPY, /* copy request */ > __REQ_NR_BITS, /* stops here */ > }; > > @@ -443,6 +444,7 @@ enum req_flag_bits { > > #define REQ_DRV (1ULL << __REQ_DRV) > #define REQ_SWAP (1ULL << __REQ_SWAP) > +#define REQ_COPY (1ULL << __REQ_COPY) > > #define REQ_FAILFAST_MASK \ > (REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER) > @@ -459,6 +461,11 @@ enum stat_group { > NR_STAT_GROUPS > }; > > +static inline bool op_is_copy(unsigned int op) > +{ > + return (op & REQ_COPY); > +} > + > #define bio_op(bio) \ > ((bio)->bi_opf & REQ_OP_MASK) > > @@ -533,4 +540,18 @@ struct blk_rq_stat { > u64 batch; > }; > > +struct cio { > + struct range_entry *rlist; naming... This is an array, right ? > + struct task_struct *waiter; /* waiting task (NULL if none) */ > + spinlock_t lock; /* protects refcount and waiter */ > + int refcount; > + blk_status_t io_err; > +}; > + > +struct copy_ctx { > + int range_idx; > + sector_t start_sec; > + struct cio *cio; > +}; > + > #endif /* __LINUX_BLK_TYPES_H */ > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h > index 3596fd37fae7..c6cb3fe82ba2 100644 > --- a/include/linux/blkdev.h > +++ b/include/linux/blkdev.h > @@ -1121,6 +1121,8 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector, > sector_t nr_sects, gfp_t gfp_mask, struct bio **biop); > int blkdev_issue_secure_erase(struct block_device *bdev, sector_t sector, > sector_t nr_sects, gfp_t gfp); > +int blkdev_issue_copy(struct block_device *src_bdev, int nr_srcs, > + struct range_entry *src_rlist, struct block_device *dest_bdev, gfp_t gfp_mask); > > #define BLKDEV_ZERO_NOUNMAP (1 << 0) /* do not free blocks */ > #define BLKDEV_ZERO_NOFALLBACK (1 << 1) /* don't write explicit zeroes */ > diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h > index bdf7b404b3e7..822c28cebf3a 100644 > --- a/include/uapi/linux/fs.h > +++ b/include/uapi/linux/fs.h > @@ -64,6 +64,20 @@ struct fstrim_range { > __u64 minlen; > }; > > +/* Maximum no of entries supported */ > +#define MAX_COPY_NR_RANGE (1 << 12) This value should be used also when setting the limits in the previous patch. max_copy_nr_ranges and max_hw_copy_nr_ranges must be bounded by it. > + > +/* maximum total copy length */ > +#define MAX_COPY_TOTAL_LENGTH (1 << 27) Same for this one. And where does this magic number come from ? > + > +/* Source range entry for copy */ > +struct range_entry { > + __u64 src; > + __u64 dst; > + __u64 len; > + __u64 comp_len; Please describe the fields of this structure. The meaning of them is really not clear from the names. > +}; > + > /* extent-same (dedupe) ioctls; these MUST match the btrfs ioctl definitions */ > #define FILE_DEDUPE_RANGE_SAME 0 > #define FILE_DEDUPE_RANGE_DIFFERS 1 -- Damien Le Moal Western Digital Research