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471 lines
12 KiB
471 lines
12 KiB
/* |
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* Copyright (C) 2020 Red Hat GmbH |
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* |
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* This file is released under the GPL. |
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* |
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* Device-mapper target to emulate smaller logical block |
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* size on backing devices exposing (natively) larger ones. |
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* |
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* E.g. 512 byte sector emulation on 4K native disks. |
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*/ |
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#include "dm.h" |
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#include <linux/module.h> |
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#include <linux/workqueue.h> |
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#include <linux/dm-bufio.h> |
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#define DM_MSG_PREFIX "ebs" |
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static void ebs_dtr(struct dm_target *ti); |
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/* Emulated block size context. */ |
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struct ebs_c { |
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struct dm_dev *dev; /* Underlying device to emulate block size on. */ |
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struct dm_bufio_client *bufio; /* Use dm-bufio for read and read-modify-write processing. */ |
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struct workqueue_struct *wq; /* Workqueue for ^ processing of bios. */ |
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struct work_struct ws; /* Work item used for ^. */ |
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struct bio_list bios_in; /* Worker bios input list. */ |
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spinlock_t lock; /* Guard bios input list above. */ |
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sector_t start; /* <start> table line argument, see ebs_ctr below. */ |
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unsigned int e_bs; /* Emulated block size in sectors exposed to upper layer. */ |
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unsigned int u_bs; /* Underlying block size in sectors retrievd from/set on lower layer device. */ |
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unsigned char block_shift; /* bitshift sectors -> blocks used in dm-bufio API. */ |
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bool u_bs_set:1; /* Flag to indicate underlying block size is set on table line. */ |
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}; |
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static inline sector_t __sector_to_block(struct ebs_c *ec, sector_t sector) |
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{ |
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return sector >> ec->block_shift; |
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} |
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static inline sector_t __block_mod(sector_t sector, unsigned int bs) |
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{ |
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return sector & (bs - 1); |
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} |
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/* Return number of blocks for a bio, accounting for misalignement of start and end sectors. */ |
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static inline unsigned int __nr_blocks(struct ebs_c *ec, struct bio *bio) |
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{ |
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sector_t end_sector = __block_mod(bio->bi_iter.bi_sector, ec->u_bs) + bio_sectors(bio); |
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return __sector_to_block(ec, end_sector) + (__block_mod(end_sector, ec->u_bs) ? 1 : 0); |
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} |
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static inline bool __ebs_check_bs(unsigned int bs) |
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{ |
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return bs && is_power_of_2(bs); |
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} |
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/* |
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* READ/WRITE: |
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* |
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* copy blocks between bufio blocks and bio vector's (partial/overlapping) pages. |
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*/ |
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static int __ebs_rw_bvec(struct ebs_c *ec, int rw, struct bio_vec *bv, struct bvec_iter *iter) |
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{ |
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int r = 0; |
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unsigned char *ba, *pa; |
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unsigned int cur_len; |
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unsigned int bv_len = bv->bv_len; |
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unsigned int buf_off = to_bytes(__block_mod(iter->bi_sector, ec->u_bs)); |
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sector_t block = __sector_to_block(ec, iter->bi_sector); |
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struct dm_buffer *b; |
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if (unlikely(!bv->bv_page || !bv_len)) |
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return -EIO; |
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pa = page_address(bv->bv_page) + bv->bv_offset; |
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/* Handle overlapping page <-> blocks */ |
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while (bv_len) { |
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cur_len = min(dm_bufio_get_block_size(ec->bufio) - buf_off, bv_len); |
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/* Avoid reading for writes in case bio vector's page overwrites block completely. */ |
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if (rw == READ || buf_off || bv_len < dm_bufio_get_block_size(ec->bufio)) |
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ba = dm_bufio_read(ec->bufio, block, &b); |
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else |
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ba = dm_bufio_new(ec->bufio, block, &b); |
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if (IS_ERR(ba)) { |
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/* |
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* Carry on with next buffer, if any, to issue all possible |
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* data but return error. |
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*/ |
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r = PTR_ERR(ba); |
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} else { |
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/* Copy data to/from bio to buffer if read/new was successful above. */ |
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ba += buf_off; |
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if (rw == READ) { |
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memcpy(pa, ba, cur_len); |
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flush_dcache_page(bv->bv_page); |
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} else { |
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flush_dcache_page(bv->bv_page); |
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memcpy(ba, pa, cur_len); |
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dm_bufio_mark_partial_buffer_dirty(b, buf_off, buf_off + cur_len); |
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} |
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dm_bufio_release(b); |
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} |
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pa += cur_len; |
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bv_len -= cur_len; |
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buf_off = 0; |
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block++; |
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} |
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return r; |
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} |
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/* READ/WRITE: iterate bio vector's copying between (partial) pages and bufio blocks. */ |
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static int __ebs_rw_bio(struct ebs_c *ec, int rw, struct bio *bio) |
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{ |
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int r = 0, rr; |
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struct bio_vec bv; |
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struct bvec_iter iter; |
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bio_for_each_bvec(bv, bio, iter) { |
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rr = __ebs_rw_bvec(ec, rw, &bv, &iter); |
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if (rr) |
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r = rr; |
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} |
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return r; |
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} |
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/* |
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* Discard bio's blocks, i.e. pass discards down. |
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* |
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* Avoid discarding partial blocks at beginning and end; |
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* return 0 in case no blocks can be discarded as a result. |
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*/ |
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static int __ebs_discard_bio(struct ebs_c *ec, struct bio *bio) |
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{ |
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sector_t block, blocks, sector = bio->bi_iter.bi_sector; |
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block = __sector_to_block(ec, sector); |
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blocks = __nr_blocks(ec, bio); |
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/* |
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* Partial first underlying block (__nr_blocks() may have |
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* resulted in one block). |
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*/ |
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if (__block_mod(sector, ec->u_bs)) { |
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block++; |
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blocks--; |
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} |
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/* Partial last underlying block if any. */ |
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if (blocks && __block_mod(bio_end_sector(bio), ec->u_bs)) |
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blocks--; |
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return blocks ? dm_bufio_issue_discard(ec->bufio, block, blocks) : 0; |
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} |
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/* Release blocks them from the bufio cache. */ |
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static void __ebs_forget_bio(struct ebs_c *ec, struct bio *bio) |
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{ |
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sector_t blocks, sector = bio->bi_iter.bi_sector; |
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blocks = __nr_blocks(ec, bio); |
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dm_bufio_forget_buffers(ec->bufio, __sector_to_block(ec, sector), blocks); |
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} |
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/* Worker funtion to process incoming bios. */ |
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static void __ebs_process_bios(struct work_struct *ws) |
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{ |
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int r; |
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bool write = false; |
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sector_t block1, block2; |
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struct ebs_c *ec = container_of(ws, struct ebs_c, ws); |
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struct bio *bio; |
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struct bio_list bios; |
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bio_list_init(&bios); |
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spin_lock_irq(&ec->lock); |
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bios = ec->bios_in; |
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bio_list_init(&ec->bios_in); |
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spin_unlock_irq(&ec->lock); |
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/* Prefetch all read and any mis-aligned write buffers */ |
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bio_list_for_each(bio, &bios) { |
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block1 = __sector_to_block(ec, bio->bi_iter.bi_sector); |
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if (bio_op(bio) == REQ_OP_READ) |
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dm_bufio_prefetch(ec->bufio, block1, __nr_blocks(ec, bio)); |
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else if (bio_op(bio) == REQ_OP_WRITE && !(bio->bi_opf & REQ_PREFLUSH)) { |
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block2 = __sector_to_block(ec, bio_end_sector(bio)); |
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if (__block_mod(bio->bi_iter.bi_sector, ec->u_bs)) |
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dm_bufio_prefetch(ec->bufio, block1, 1); |
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if (__block_mod(bio_end_sector(bio), ec->u_bs) && block2 != block1) |
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dm_bufio_prefetch(ec->bufio, block2, 1); |
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} |
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} |
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bio_list_for_each(bio, &bios) { |
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r = -EIO; |
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if (bio_op(bio) == REQ_OP_READ) |
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r = __ebs_rw_bio(ec, READ, bio); |
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else if (bio_op(bio) == REQ_OP_WRITE) { |
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write = true; |
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r = __ebs_rw_bio(ec, WRITE, bio); |
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} else if (bio_op(bio) == REQ_OP_DISCARD) { |
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__ebs_forget_bio(ec, bio); |
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r = __ebs_discard_bio(ec, bio); |
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} |
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if (r < 0) |
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bio->bi_status = errno_to_blk_status(r); |
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} |
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/* |
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* We write dirty buffers after processing I/O on them |
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* but before we endio thus addressing REQ_FUA/REQ_SYNC. |
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*/ |
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r = write ? dm_bufio_write_dirty_buffers(ec->bufio) : 0; |
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while ((bio = bio_list_pop(&bios))) { |
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/* Any other request is endioed. */ |
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if (unlikely(r && bio_op(bio) == REQ_OP_WRITE)) |
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bio_io_error(bio); |
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else |
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bio_endio(bio); |
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} |
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} |
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/* |
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* Construct an emulated block size mapping: <dev_path> <offset> <ebs> [<ubs>] |
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* |
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* <dev_path>: path of the underlying device |
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* <offset>: offset in 512 bytes sectors into <dev_path> |
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* <ebs>: emulated block size in units of 512 bytes exposed to the upper layer |
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* [<ubs>]: underlying block size in units of 512 bytes imposed on the lower layer; |
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* optional, if not supplied, retrieve logical block size from underlying device |
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*/ |
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static int ebs_ctr(struct dm_target *ti, unsigned int argc, char **argv) |
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{ |
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int r; |
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unsigned short tmp1; |
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unsigned long long tmp; |
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char dummy; |
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struct ebs_c *ec; |
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if (argc < 3 || argc > 4) { |
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ti->error = "Invalid argument count"; |
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return -EINVAL; |
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} |
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ec = ti->private = kzalloc(sizeof(*ec), GFP_KERNEL); |
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if (!ec) { |
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ti->error = "Cannot allocate ebs context"; |
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return -ENOMEM; |
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} |
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r = -EINVAL; |
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if (sscanf(argv[1], "%llu%c", &tmp, &dummy) != 1 || |
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tmp != (sector_t)tmp || |
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(sector_t)tmp >= ti->len) { |
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ti->error = "Invalid device offset sector"; |
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goto bad; |
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} |
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ec->start = tmp; |
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if (sscanf(argv[2], "%hu%c", &tmp1, &dummy) != 1 || |
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!__ebs_check_bs(tmp1) || |
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to_bytes(tmp1) > PAGE_SIZE) { |
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ti->error = "Invalid emulated block size"; |
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goto bad; |
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} |
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ec->e_bs = tmp1; |
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if (argc > 3) { |
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if (sscanf(argv[3], "%hu%c", &tmp1, &dummy) != 1 || !__ebs_check_bs(tmp1)) { |
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ti->error = "Invalid underlying block size"; |
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goto bad; |
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} |
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ec->u_bs = tmp1; |
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ec->u_bs_set = true; |
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} else |
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ec->u_bs_set = false; |
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r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &ec->dev); |
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if (r) { |
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ti->error = "Device lookup failed"; |
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ec->dev = NULL; |
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goto bad; |
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} |
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r = -EINVAL; |
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if (!ec->u_bs_set) { |
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ec->u_bs = to_sector(bdev_logical_block_size(ec->dev->bdev)); |
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if (!__ebs_check_bs(ec->u_bs)) { |
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ti->error = "Invalid retrieved underlying block size"; |
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goto bad; |
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} |
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} |
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if (!ec->u_bs_set && ec->e_bs == ec->u_bs) |
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DMINFO("Emulation superfluous: emulated equal to underlying block size"); |
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if (__block_mod(ec->start, ec->u_bs)) { |
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ti->error = "Device offset must be multiple of underlying block size"; |
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goto bad; |
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} |
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ec->bufio = dm_bufio_client_create(ec->dev->bdev, to_bytes(ec->u_bs), 1, 0, NULL, NULL); |
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if (IS_ERR(ec->bufio)) { |
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ti->error = "Cannot create dm bufio client"; |
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r = PTR_ERR(ec->bufio); |
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ec->bufio = NULL; |
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goto bad; |
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} |
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ec->wq = alloc_ordered_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM); |
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if (!ec->wq) { |
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ti->error = "Cannot create dm-" DM_MSG_PREFIX " workqueue"; |
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r = -ENOMEM; |
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goto bad; |
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} |
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ec->block_shift = __ffs(ec->u_bs); |
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INIT_WORK(&ec->ws, &__ebs_process_bios); |
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bio_list_init(&ec->bios_in); |
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spin_lock_init(&ec->lock); |
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ti->num_flush_bios = 1; |
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ti->num_discard_bios = 1; |
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ti->num_secure_erase_bios = 0; |
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ti->num_write_same_bios = 0; |
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ti->num_write_zeroes_bios = 0; |
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return 0; |
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bad: |
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ebs_dtr(ti); |
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return r; |
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} |
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static void ebs_dtr(struct dm_target *ti) |
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{ |
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struct ebs_c *ec = ti->private; |
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if (ec->wq) |
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destroy_workqueue(ec->wq); |
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if (ec->bufio) |
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dm_bufio_client_destroy(ec->bufio); |
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if (ec->dev) |
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dm_put_device(ti, ec->dev); |
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kfree(ec); |
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} |
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static int ebs_map(struct dm_target *ti, struct bio *bio) |
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{ |
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struct ebs_c *ec = ti->private; |
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bio_set_dev(bio, ec->dev->bdev); |
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bio->bi_iter.bi_sector = ec->start + dm_target_offset(ti, bio->bi_iter.bi_sector); |
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if (unlikely(bio_op(bio) == REQ_OP_FLUSH)) |
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return DM_MAPIO_REMAPPED; |
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/* |
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* Only queue for bufio processing in case of partial or overlapping buffers |
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* -or- |
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* emulation with ebs == ubs aiming for tests of dm-bufio overhead. |
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*/ |
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if (likely(__block_mod(bio->bi_iter.bi_sector, ec->u_bs) || |
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__block_mod(bio_end_sector(bio), ec->u_bs) || |
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ec->e_bs == ec->u_bs)) { |
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spin_lock_irq(&ec->lock); |
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bio_list_add(&ec->bios_in, bio); |
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spin_unlock_irq(&ec->lock); |
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queue_work(ec->wq, &ec->ws); |
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return DM_MAPIO_SUBMITTED; |
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} |
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/* Forget any buffer content relative to this direct backing device I/O. */ |
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__ebs_forget_bio(ec, bio); |
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return DM_MAPIO_REMAPPED; |
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} |
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static void ebs_status(struct dm_target *ti, status_type_t type, |
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unsigned status_flags, char *result, unsigned maxlen) |
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{ |
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struct ebs_c *ec = ti->private; |
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switch (type) { |
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case STATUSTYPE_INFO: |
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*result = '\0'; |
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break; |
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case STATUSTYPE_TABLE: |
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snprintf(result, maxlen, ec->u_bs_set ? "%s %llu %u %u" : "%s %llu %u", |
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ec->dev->name, (unsigned long long) ec->start, ec->e_bs, ec->u_bs); |
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break; |
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} |
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} |
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static int ebs_prepare_ioctl(struct dm_target *ti, struct block_device **bdev) |
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{ |
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struct ebs_c *ec = ti->private; |
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struct dm_dev *dev = ec->dev; |
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/* |
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* Only pass ioctls through if the device sizes match exactly. |
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*/ |
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*bdev = dev->bdev; |
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return !!(ec->start || ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT); |
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} |
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static void ebs_io_hints(struct dm_target *ti, struct queue_limits *limits) |
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{ |
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struct ebs_c *ec = ti->private; |
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limits->logical_block_size = to_bytes(ec->e_bs); |
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limits->physical_block_size = to_bytes(ec->u_bs); |
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limits->alignment_offset = limits->physical_block_size; |
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blk_limits_io_min(limits, limits->logical_block_size); |
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} |
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static int ebs_iterate_devices(struct dm_target *ti, |
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iterate_devices_callout_fn fn, void *data) |
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{ |
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struct ebs_c *ec = ti->private; |
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return fn(ti, ec->dev, ec->start, ti->len, data); |
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} |
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static struct target_type ebs_target = { |
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.name = "ebs", |
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.version = {1, 0, 1}, |
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.features = DM_TARGET_PASSES_INTEGRITY, |
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.module = THIS_MODULE, |
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.ctr = ebs_ctr, |
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.dtr = ebs_dtr, |
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.map = ebs_map, |
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.status = ebs_status, |
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.io_hints = ebs_io_hints, |
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.prepare_ioctl = ebs_prepare_ioctl, |
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.iterate_devices = ebs_iterate_devices, |
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}; |
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static int __init dm_ebs_init(void) |
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{ |
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int r = dm_register_target(&ebs_target); |
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if (r < 0) |
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DMERR("register failed %d", r); |
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return r; |
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} |
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static void dm_ebs_exit(void) |
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{ |
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dm_unregister_target(&ebs_target); |
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} |
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module_init(dm_ebs_init); |
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module_exit(dm_ebs_exit); |
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MODULE_AUTHOR("Heinz Mauelshagen <[email protected]>"); |
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MODULE_DESCRIPTION(DM_NAME " emulated block size target"); |
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MODULE_LICENSE("GPL");
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