[PATCH] Add scatter-gather support for the block layer SG_IO
Signed-off-by: Jens Axboe <axboe@suse.de>
This commit is contained in:
James Bottomley
Jens Axboe
Родитель
dd1cab95f3
Коммит
f1970baf6d
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@ -2148,6 +2148,50 @@ int blk_rq_map_user(request_queue_t *q, struct request *rq, void __user *ubuf,
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EXPORT_SYMBOL(blk_rq_map_user);
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/**
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* blk_rq_map_user_iov - map user data to a request, for REQ_BLOCK_PC usage
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* @q: request queue where request should be inserted
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* @rq: request to map data to
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* @iov: pointer to the iovec
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* @iov_count: number of elements in the iovec
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*
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* Description:
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* Data will be mapped directly for zero copy io, if possible. Otherwise
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* a kernel bounce buffer is used.
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*
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* A matching blk_rq_unmap_user() must be issued at the end of io, while
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* still in process context.
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*
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* Note: The mapped bio may need to be bounced through blk_queue_bounce()
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* before being submitted to the device, as pages mapped may be out of
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* reach. It's the callers responsibility to make sure this happens. The
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* original bio must be passed back in to blk_rq_unmap_user() for proper
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* unmapping.
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*/
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int blk_rq_map_user_iov(request_queue_t *q, struct request *rq,
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struct sg_iovec *iov, int iov_count)
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{
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struct bio *bio;
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if (!iov || iov_count <= 0)
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return -EINVAL;
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/* we don't allow misaligned data like bio_map_user() does. If the
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* user is using sg, they're expected to know the alignment constraints
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* and respect them accordingly */
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bio = bio_map_user_iov(q, NULL, iov, iov_count, rq_data_dir(rq)== READ);
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if (IS_ERR(bio))
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return PTR_ERR(bio);
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rq->bio = rq->biotail = bio;
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blk_rq_bio_prep(q, rq, bio);
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rq->buffer = rq->data = NULL;
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rq->data_len = bio->bi_size;
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return 0;
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}
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EXPORT_SYMBOL(blk_rq_map_user_iov);
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/**
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* blk_rq_unmap_user - unmap a request with user data
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* @rq: request to be unmapped
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@ -2207,6 +2251,19 @@ int blk_rq_map_kern(request_queue_t *q, struct request *rq, void *kbuf,
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EXPORT_SYMBOL(blk_rq_map_kern);
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void blk_execute_rq_nowait(request_queue_t *q, struct gendisk *bd_disk,
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struct request *rq, int at_head,
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void (*done)(struct request *))
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{
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int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
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rq->rq_disk = bd_disk;
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rq->flags |= REQ_NOMERGE;
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rq->end_io = done;
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elv_add_request(q, rq, where, 1);
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generic_unplug_device(q);
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}
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/**
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* blk_execute_rq - insert a request into queue for execution
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* @q: queue to insert the request in
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@ -2224,8 +2281,6 @@ int blk_execute_rq(request_queue_t *q, struct gendisk *bd_disk,
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char sense[SCSI_SENSE_BUFFERSIZE];
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int err = 0;
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rq->rq_disk = bd_disk;
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/*
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* we need an extra reference to the request, so we can look at
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* it after io completion
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@ -2238,11 +2293,8 @@ int blk_execute_rq(request_queue_t *q, struct gendisk *bd_disk,
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rq->sense_len = 0;
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}
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rq->flags |= REQ_NOMERGE;
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rq->waiting = &wait;
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rq->end_io = blk_end_sync_rq;
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elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 1);
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generic_unplug_device(q);
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blk_execute_rq_nowait(q, bd_disk, rq, 0, blk_end_sync_rq);
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wait_for_completion(&wait);
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rq->waiting = NULL;
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@ -231,17 +231,11 @@ static int sg_io(struct file *file, request_queue_t *q,
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if (verify_command(file, cmd))
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return -EPERM;
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/*
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* we'll do that later
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*/
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if (hdr->iovec_count)
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return -EOPNOTSUPP;
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if (hdr->dxfer_len > (q->max_sectors << 9))
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return -EIO;
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reading = writing = 0;
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if (hdr->dxfer_len) {
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if (hdr->dxfer_len)
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switch (hdr->dxfer_direction) {
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default:
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return -EINVAL;
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@ -261,11 +255,29 @@ static int sg_io(struct file *file, request_queue_t *q,
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if (!rq)
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return -ENOMEM;
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if (reading || writing) {
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ret = blk_rq_map_user(q, rq, hdr->dxferp, hdr->dxfer_len);
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if (ret)
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if (hdr->iovec_count) {
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const int size = sizeof(struct sg_iovec) * hdr->iovec_count;
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struct sg_iovec *iov;
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iov = kmalloc(size, GFP_KERNEL);
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if (!iov) {
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ret = -ENOMEM;
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goto out;
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}
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}
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if (copy_from_user(iov, hdr->dxferp, size)) {
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kfree(iov);
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ret = -EFAULT;
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goto out;
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}
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ret = blk_rq_map_user_iov(q, rq, iov, hdr->iovec_count);
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kfree(iov);
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} else if (hdr->dxfer_len)
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ret = blk_rq_map_user(q, rq, hdr->dxferp, hdr->dxfer_len);
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if (ret)
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goto out;
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/*
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* fill in request structure
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142
fs/bio.c
142
fs/bio.c
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@ -25,6 +25,7 @@
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#include <linux/module.h>
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#include <linux/mempool.h>
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#include <linux/workqueue.h>
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#include <scsi/sg.h> /* for struct sg_iovec */
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#define BIO_POOL_SIZE 256
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@ -549,22 +550,34 @@ out_bmd:
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return ERR_PTR(ret);
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}
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static struct bio *__bio_map_user(request_queue_t *q, struct block_device *bdev,
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unsigned long uaddr, unsigned int len,
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int write_to_vm)
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static struct bio *__bio_map_user_iov(request_queue_t *q,
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struct block_device *bdev,
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struct sg_iovec *iov, int iov_count,
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int write_to_vm)
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{
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unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
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unsigned long start = uaddr >> PAGE_SHIFT;
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const int nr_pages = end - start;
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int ret, offset, i;
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int i, j;
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int nr_pages = 0;
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struct page **pages;
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struct bio *bio;
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int cur_page = 0;
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int ret, offset;
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/*
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* transfer and buffer must be aligned to at least hardsector
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* size for now, in the future we can relax this restriction
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*/
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if ((uaddr & queue_dma_alignment(q)) || (len & queue_dma_alignment(q)))
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for (i = 0; i < iov_count; i++) {
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unsigned long uaddr = (unsigned long)iov[i].iov_base;
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unsigned long len = iov[i].iov_len;
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unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
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unsigned long start = uaddr >> PAGE_SHIFT;
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nr_pages += end - start;
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/*
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* transfer and buffer must be aligned to at least hardsector
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* size for now, in the future we can relax this restriction
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*/
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if ((uaddr & queue_dma_alignment(q)) || (len & queue_dma_alignment(q)))
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return ERR_PTR(-EINVAL);
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}
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if (!nr_pages)
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return ERR_PTR(-EINVAL);
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bio = bio_alloc(GFP_KERNEL, nr_pages);
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@ -576,42 +589,54 @@ static struct bio *__bio_map_user(request_queue_t *q, struct block_device *bdev,
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if (!pages)
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goto out;
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down_read(¤t->mm->mmap_sem);
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ret = get_user_pages(current, current->mm, uaddr, nr_pages,
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write_to_vm, 0, pages, NULL);
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up_read(¤t->mm->mmap_sem);
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memset(pages, 0, nr_pages * sizeof(struct page *));
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if (ret < nr_pages)
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goto out;
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for (i = 0; i < iov_count; i++) {
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unsigned long uaddr = (unsigned long)iov[i].iov_base;
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unsigned long len = iov[i].iov_len;
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unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
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unsigned long start = uaddr >> PAGE_SHIFT;
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const int local_nr_pages = end - start;
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const int page_limit = cur_page + local_nr_pages;
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down_read(¤t->mm->mmap_sem);
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ret = get_user_pages(current, current->mm, uaddr,
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local_nr_pages,
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write_to_vm, 0, &pages[cur_page], NULL);
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up_read(¤t->mm->mmap_sem);
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bio->bi_bdev = bdev;
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if (ret < local_nr_pages)
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goto out_unmap;
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offset = uaddr & ~PAGE_MASK;
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for (i = 0; i < nr_pages; i++) {
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unsigned int bytes = PAGE_SIZE - offset;
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if (len <= 0)
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break;
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offset = uaddr & ~PAGE_MASK;
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for (j = cur_page; j < page_limit; j++) {
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unsigned int bytes = PAGE_SIZE - offset;
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if (bytes > len)
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bytes = len;
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if (len <= 0)
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break;
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if (bytes > len)
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bytes = len;
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/*
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* sorry...
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*/
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if (__bio_add_page(q, bio, pages[j], bytes, offset) < bytes)
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break;
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len -= bytes;
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offset = 0;
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}
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cur_page = j;
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/*
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* sorry...
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* release the pages we didn't map into the bio, if any
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*/
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if (__bio_add_page(q, bio, pages[i], bytes, offset) < bytes)
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break;
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len -= bytes;
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offset = 0;
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while (j < page_limit)
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page_cache_release(pages[j++]);
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}
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/*
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* release the pages we didn't map into the bio, if any
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*/
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while (i < nr_pages)
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page_cache_release(pages[i++]);
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kfree(pages);
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/*
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@ -620,9 +645,17 @@ static struct bio *__bio_map_user(request_queue_t *q, struct block_device *bdev,
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if (!write_to_vm)
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bio->bi_rw |= (1 << BIO_RW);
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bio->bi_bdev = bdev;
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bio->bi_flags |= (1 << BIO_USER_MAPPED);
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return bio;
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out:
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out_unmap:
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for (i = 0; i < nr_pages; i++) {
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if(!pages[i])
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break;
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page_cache_release(pages[i]);
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}
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out:
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kfree(pages);
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bio_put(bio);
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return ERR_PTR(ret);
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@ -642,9 +675,33 @@ out:
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struct bio *bio_map_user(request_queue_t *q, struct block_device *bdev,
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unsigned long uaddr, unsigned int len, int write_to_vm)
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{
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struct bio *bio;
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struct sg_iovec iov;
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bio = __bio_map_user(q, bdev, uaddr, len, write_to_vm);
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iov.iov_base = (__user void *)uaddr;
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iov.iov_len = len;
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return bio_map_user_iov(q, bdev, &iov, 1, write_to_vm);
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}
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/**
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* bio_map_user_iov - map user sg_iovec table into bio
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* @q: the request_queue_t for the bio
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* @bdev: destination block device
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* @iov: the iovec.
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* @iov_count: number of elements in the iovec
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* @write_to_vm: bool indicating writing to pages or not
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*
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* Map the user space address into a bio suitable for io to a block
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* device. Returns an error pointer in case of error.
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*/
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struct bio *bio_map_user_iov(request_queue_t *q, struct block_device *bdev,
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struct sg_iovec *iov, int iov_count,
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int write_to_vm)
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{
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struct bio *bio;
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int len = 0, i;
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bio = __bio_map_user_iov(q, bdev, iov, iov_count, write_to_vm);
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if (IS_ERR(bio))
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return bio;
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@ -657,6 +714,9 @@ struct bio *bio_map_user(request_queue_t *q, struct block_device *bdev,
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*/
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bio_get(bio);
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for (i = 0; i < iov_count; i++)
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len += iov[i].iov_len;
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if (bio->bi_size == len)
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return bio;
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@ -281,6 +281,10 @@ extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
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extern int bio_get_nr_vecs(struct block_device *);
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extern struct bio *bio_map_user(struct request_queue *, struct block_device *,
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unsigned long, unsigned int, int);
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struct sg_iovec;
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extern struct bio *bio_map_user_iov(struct request_queue *,
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struct block_device *,
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struct sg_iovec *, int, int);
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extern void bio_unmap_user(struct bio *);
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extern struct bio *bio_map_kern(struct request_queue *, void *, unsigned int,
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unsigned int);
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@ -561,6 +561,7 @@ extern void blk_queue_activity_fn(request_queue_t *, activity_fn *, void *);
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extern int blk_rq_map_user(request_queue_t *, struct request *, void __user *, unsigned int);
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extern int blk_rq_unmap_user(struct bio *, unsigned int);
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extern int blk_rq_map_kern(request_queue_t *, struct request *, void *, unsigned int, unsigned int);
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extern int blk_rq_map_user_iov(request_queue_t *, struct request *, struct sg_iovec *, int);
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extern int blk_execute_rq(request_queue_t *, struct gendisk *, struct request *);
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static inline request_queue_t *bdev_get_queue(struct block_device *bdev)
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