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Date: Tue, 18 Oct 2011 16:46:00 -0400
From: Stephen Bromfield <s.bromfield@...il.com>
To: linux-kernel@...r.kernel.org
Subject: [RFC][PATCH] dm-cache (block level disk cache target): UPDATE
A new patch for the 2.6.39 kernel. Please CC all comments to
dm-cache@...glegroups.com.
Signed-off-by: Ming Zhao <dm-cache@...glegroups.com>
diff -Naur linux-2.6.39.1/drivers/md/dm-cache.c
linux-2.6.39.1-dm-cache/drivers/md/dm-cache.c
--- linux-2.6.39.1/drivers/md/dm-cache.c 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.39.1-dm-cache/drivers/md/dm-cache.c 2011-10-17
18:58:59.000000000 +0000
@@ -0,0 +1,1806 @@
+/****************************************************************************
+ * dm-cache.c
+ * Device mapper target for block-level disk caching
+ *
+ * Copyright (C) International Business Machines Corp., 2006
+ * Copyright (C) Ming Zhao, Florida International University, 2007-2009
+ *
+ * Authors: Ming Zhao, Stephen Bromfield, Douglas Otstott,
+ * Dulcardo Clavijo (dm-cache@...glegroups.com)
+ * Other contributors:
+ * Eric Van Hensbergen, Reng Zeng
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; under version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ ****************************************************************************/
+#include <linux/blk_types.h>
+#include <asm/atomic.h>
+#include <asm/checksum.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/blkdev.h>
+#include <linux/bio.h>
+#include <linux/slab.h>
+#include <linux/hash.h>
+#include <linux/spinlock.h>
+#include <linux/workqueue.h>
+#include <linux/pagemap.h>
+#include "dm.h"
+#include <linux/dm-io.h>
+#include <linux/dm-kcopyd.h>
+
+#define DMC_DEBUG 0
+
+#define DM_MSG_PREFIX "cache"
+#define DMC_PREFIX "dm-cache: "
+
+#if DMC_DEBUG
+#define DPRINTK( s, arg... ) printk(DMC_PREFIX s "\n", ##arg)
+#else
+#define DPRINTK( s, arg... )
+#endif
+
+/* Default cache parameters */
+#define DEFAULT_CACHE_SIZE 65536
+#define DEFAULT_CACHE_ASSOC 1024
+#define DEFAULT_BLOCK_SIZE 8
+#define CONSECUTIVE_BLOCKS 512
+
+/* Write policy */
+#define WRITE_THROUGH 0
+#define WRITE_BACK 1
+#define DEFAULT_WRITE_POLICY WRITE_THROUGH
+
+/* Number of pages for I/O */
+#define DMCACHE_COPY_PAGES 1024
+
+/* States of a cache block */
+#define INVALID 0
+#define VALID 1 /* Valid */
+#define RESERVED 2 /* Allocated but data not in place yet */
+#define DIRTY 4 /* Locally modified */
+#define WRITEBACK 8 /* In the process of write back */
+
+#define is_state(x, y) (x & y)
+#define set_state(x, y) (x |= y)
+#define clear_state(x, y) (x &= ~y)
+
+/*
+ * Cache context
+ */
+struct cache_c {
+ struct dm_dev *src_dev; /* Source device */
+ struct dm_dev *cache_dev; /* Cache device */
+ struct dm_kcopyd_client *kcp_client; /* Kcopyd client for writing back data */
+
+ struct cacheblock *cache; /* Hash table for cache blocks */
+ sector_t size; /* Cache size */
+ unsigned int bits; /* Cache size in bits */
+ unsigned int assoc; /* Cache associativity */
+ unsigned int block_size; /* Cache block size */
+ unsigned int block_shift; /* Cache block size in bits */
+ unsigned int block_mask; /* Cache block mask */
+ unsigned int consecutive_shift; /* Consecutive blocks size in bits */
+ unsigned long counter; /* Logical timestamp of last access */
+ unsigned int write_policy; /* Cache write policy */
+ sector_t dirty_blocks; /* Number of dirty blocks */
+
+ spinlock_t lock; /* Lock to protect page allocation/deallocation */
+ struct page_list *pages; /* Pages for I/O */
+ unsigned int nr_pages; /* Number of pages */
+ unsigned int nr_free_pages; /* Number of free pages */
+ wait_queue_head_t destroyq; /* Wait queue for I/O completion */
+ atomic_t nr_jobs; /* Number of I/O jobs */
+ struct dm_io_client *io_client; /* Client memory pool*/
+
+ /* Stats */
+ unsigned long reads; /* Number of reads */
+ unsigned long writes; /* Number of writes */
+ unsigned long cache_hits; /* Number of cache hits */
+ unsigned long replace; /* Number of cache replacements */
+ unsigned long writeback; /* Number of replaced dirty blocks */
+ unsigned long dirty; /* Number of submitted dirty blocks */
+};
+
+/* Cache block metadata structure */
+struct cacheblock {
+ spinlock_t lock; /* Lock to protect operations on the bio list */
+ sector_t block; /* Sector number of the cached block */
+ unsigned short state; /* State of a block */
+ unsigned long counter; /* Logical timestamp of the block's last access */
+ struct bio_list bios; /* List of pending bios */
+};
+
+/* Structure for a kcached job */
+struct kcached_job {
+ struct list_head list;
+ struct cache_c *dmc;
+ struct bio *bio; /* Original bio */
+ struct dm_io_region src;
+ struct dm_io_region dest;
+ struct cacheblock *cacheblock;
+ int rw;
+ /*
+ * When the original bio is not aligned with cache blocks,
+ * we need extra bvecs and pages for padding.
+ */
+ struct bio_vec *bvec;
+ unsigned int nr_pages;
+ struct page_list *pages;
+};
+
+
+/****************************************************************************
+ * Wrapper functions for using the new dm_io API
+ ****************************************************************************/
+static int dm_io_sync_vm(unsigned int num_regions, struct dm_io_region
+ *where, int rw, void *data, unsigned long *error_bits, struct cache_c *dmc)
+{
+ struct dm_io_request iorq;
+
+ iorq.bi_rw= rw;
+ iorq.mem.type = DM_IO_VMA;
+ iorq.mem.ptr.vma = data;
+ iorq.notify.fn = NULL;
+ iorq.client = dmc->io_client;
+
+ return dm_io(&iorq, num_regions, where, error_bits);
+}
+
+static int dm_io_async_bvec(unsigned int num_regions, struct dm_io_region
+ *where, int rw, struct bio_vec *bvec, io_notify_fn fn, void *context)
+{
+ struct kcached_job *job = (struct kcached_job *)context;
+ struct cache_c *dmc = job->dmc;
+ struct dm_io_request iorq;
+
+ iorq.bi_rw = (rw | (1 << REQ_SYNC));
+ iorq.mem.type = DM_IO_BVEC;
+ iorq.mem.ptr.bvec = bvec;
+ iorq.notify.fn = fn;
+ iorq.notify.context = context;
+ iorq.client = dmc->io_client;
+
+ return dm_io(&iorq, num_regions, where, NULL);
+}
+
+
+/****************************************************************************
+ * Functions and data structures for implementing a kcached to handle async
+ * I/O. Code for page and queue handling is borrowed from kcopyd.c.
+ ****************************************************************************/
+
+/*
+ * Functions for handling pages used by async I/O.
+ * The data asked by a bio request may not be aligned with cache blocks, in
+ * which case additional pages are required for the request that is forwarded
+ * to the server. A pool of pages are reserved for this purpose.
+ */
+
+static struct page_list *alloc_pl(void)
+{
+ struct page_list *pl;
+
+ pl = kmalloc(sizeof(*pl), GFP_KERNEL);
+ if (!pl)
+ return NULL;
+
+ pl->page = alloc_page(GFP_KERNEL);
+ if (!pl->page) {
+ kfree(pl);
+ return NULL;
+ }
+
+ return pl;
+}
+
+static void free_pl(struct page_list *pl)
+{
+ __free_page(pl->page);
+ kfree(pl);
+}
+
+static void drop_pages(struct page_list *pl)
+{
+ struct page_list *next;
+
+ while (pl) {
+ next = pl->next;
+ free_pl(pl);
+ pl = next;
+ }
+}
+
+static int kcached_get_pages(struct cache_c *dmc, unsigned int nr,
+ struct page_list **pages)
+{
+ struct page_list *pl;
+
+ spin_lock(&dmc->lock);
+ if (dmc->nr_free_pages < nr) {
+ DPRINTK("kcached_get_pages: No free pages: %u<%u",
+ dmc->nr_free_pages, nr);
+ spin_unlock(&dmc->lock);
+ return -ENOMEM;
+ }
+
+ dmc->nr_free_pages -= nr;
+ for (*pages = pl = dmc->pages; --nr; pl = pl->next)
+ ;
+
+ dmc->pages = pl->next;
+ pl->next = NULL;
+
+ spin_unlock(&dmc->lock);
+
+ return 0;
+}
+
+static void kcached_put_pages(struct cache_c *dmc, struct page_list *pl)
+{
+ struct page_list *cursor;
+
+ spin_lock(&dmc->lock);
+ for (cursor = pl; cursor->next; cursor = cursor->next)
+ dmc->nr_free_pages++;
+
+ dmc->nr_free_pages++;
+ cursor->next = dmc->pages;
+ dmc->pages = pl;
+
+ spin_unlock(&dmc->lock);
+}
+
+static int alloc_bio_pages(struct cache_c *dmc, unsigned int nr)
+{
+ unsigned int i;
+ struct page_list *pl = NULL, *next;
+
+ for (i = 0; i < nr; i++) {
+ next = alloc_pl();
+ if (!next) {
+ if (pl)
+ drop_pages(pl);
+ return -ENOMEM;
+ }
+ next->next = pl;
+ pl = next;
+ }
+
+ kcached_put_pages(dmc, pl);
+ dmc->nr_pages += nr;
+
+ return 0;
+}
+
+static void free_bio_pages(struct cache_c *dmc)
+{
+ BUG_ON(dmc->nr_free_pages != dmc->nr_pages);
+ drop_pages(dmc->pages);
+ dmc->pages = NULL;
+ dmc->nr_free_pages = dmc->nr_pages = 0;
+}
+
+static struct workqueue_struct *_kcached_wq;
+static struct work_struct _kcached_work;
+
+static inline void wake(void)
+{
+ queue_work(_kcached_wq, &_kcached_work);
+}
+
+#define MIN_JOBS 1024
+
+static struct kmem_cache *_job_cache;
+static mempool_t *_job_pool;
+
+static DEFINE_SPINLOCK(_job_lock);
+
+static LIST_HEAD(_complete_jobs);
+static LIST_HEAD(_io_jobs);
+static LIST_HEAD(_pages_jobs);
+
+static int jobs_init(void)
+{
+ _job_cache = kmem_cache_create("kcached-jobs",
+ sizeof(struct kcached_job),
+ __alignof__(struct kcached_job),
+ 0, NULL);
+ if (!_job_cache)
+ return -ENOMEM;
+
+ _job_pool = mempool_create(MIN_JOBS, mempool_alloc_slab,
+ mempool_free_slab, _job_cache);
+ if (!_job_pool) {
+ kmem_cache_destroy(_job_cache);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+static void jobs_exit(void)
+{
+ BUG_ON(!list_empty(&_complete_jobs));
+ BUG_ON(!list_empty(&_io_jobs));
+ BUG_ON(!list_empty(&_pages_jobs));
+
+ mempool_destroy(_job_pool);
+ kmem_cache_destroy(_job_cache);
+ _job_pool = NULL;
+ _job_cache = NULL;
+}
+
+/*
+ * Functions to push and pop a job onto the head of a given job list.
+ */
+static inline struct kcached_job *pop(struct list_head *jobs)
+{
+ struct kcached_job *job = NULL;
+ unsigned long flags;
+
+ spin_lock_irqsave(&_job_lock, flags);
+
+ if (!list_empty(jobs)) {
+ job = list_entry(jobs->next, struct kcached_job, list);
+ list_del(&job->list);
+ }
+ spin_unlock_irqrestore(&_job_lock, flags);
+
+ return job;
+}
+
+static inline void push(struct list_head *jobs, struct kcached_job *job)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&_job_lock, flags);
+ list_add_tail(&job->list, jobs);
+ spin_unlock_irqrestore(&_job_lock, flags);
+}
+
+
+/****************************************************************************
+ * Functions for asynchronously fetching data from source device and storing
+ * data in cache device. Because the requested data may not align with the
+ * cache blocks, extra handling is required to pad a block request and extract
+ * the requested data from the results.
+ ****************************************************************************/
+
+static void io_callback(unsigned long error, void *context)
+{
+ struct kcached_job *job = (struct kcached_job *) context;
+
+ if (error) {
+ /* TODO */
+ DMERR("io_callback: io error");
+ return;
+ }
+
+ if (job->rw == READ) {
+ job->rw = WRITE;
+ push(&_io_jobs, job);
+ } else
+ push(&_complete_jobs, job);
+ wake();
+}
+
+/*
+ * Fetch data from the source device asynchronously.
+ * For a READ bio, if a cache block is larger than the requested data, then
+ * additional data are prefetched. Larger cache block size enables more
+ * aggressive read prefetching, which is useful for read-mostly usage.
+ * For a WRITE bio, if a cache block is larger than the requested data, the
+ * entire block needs to be fetched, and larger block size incurs
more overhead.
+ * In scenaros where writes are frequent, 4KB is a good cache block size.
+ */
+static int do_fetch(struct kcached_job *job)
+{
+ int r = 0, i, j;
+ struct bio *bio = job->bio;
+ struct cache_c *dmc = job->dmc;
+ unsigned int offset, head, tail, remaining, nr_vecs, idx = 0;
+ struct bio_vec *bvec;
+ struct page_list *pl;
+
+ offset = (unsigned int) (bio->bi_sector & dmc->block_mask);
+ head = to_bytes(offset);
+ tail = to_bytes(dmc->block_size) - bio->bi_size - head;
+
+ DPRINTK("do_fetch: %llu(%llu->%llu,%llu), head:%u,tail:%u",
+ bio->bi_sector, job->src.sector, job->dest.sector,
+ job->src.count, head, tail);
+
+ if (bio_data_dir(bio) == READ) { /* The original request is a READ */
+ if (0 == job->nr_pages) { /* The request is aligned to cache block */
+ r = dm_io_async_bvec(1, &job->src, READ,
+ bio->bi_io_vec + bio->bi_idx,
+ io_callback, job);
+ return r;
+ }
+
+ nr_vecs = bio->bi_vcnt - bio->bi_idx + job->nr_pages;
+ bvec = kmalloc(nr_vecs * sizeof(*bvec), GFP_NOIO);
+ if (!bvec) {
+ DMERR("do_fetch: No memory");
+ return 1;
+ }
+
+ pl = job->pages;
+ i = 0;
+ while (head) {
+ bvec[i].bv_len = min(head, (unsigned int)PAGE_SIZE);
+ bvec[i].bv_offset = 0;
+ bvec[i].bv_page = pl->page;
+ head -= bvec[i].bv_len;
+ pl = pl->next;
+ i++;
+ }
+
+ remaining = bio->bi_size;
+ j = bio->bi_idx;
+ while (remaining) {
+ bvec[i] = bio->bi_io_vec[j];
+ remaining -= bvec[i].bv_len;
+ i++; j++;
+ }
+
+ while (tail) {
+ bvec[i].bv_len = min(tail, (unsigned int)PAGE_SIZE);
+ bvec[i].bv_offset = 0;
+ bvec[i].bv_page = pl->page;
+ tail -= bvec[i].bv_len;
+ pl = pl->next;
+ i++;
+ }
+
+ job->bvec = bvec;
+ r = dm_io_async_bvec(1, &job->src, READ, job->bvec, io_callback, job);
+ return r;
+ } else { /* The original request is a WRITE */
+ pl = job->pages;
+
+ if (head && tail) { /* Special case */
+ bvec = kmalloc(job->nr_pages * sizeof(*bvec), GFP_KERNEL);
+ if (!bvec) {
+ DMERR("do_fetch: No memory");
+ return 1;
+ }
+ for (i=0; i<job->nr_pages; i++) {
+ bvec[i].bv_len = PAGE_SIZE;
+ bvec[i].bv_offset = 0;
+ bvec[i].bv_page = pl->page;
+ pl = pl->next;
+ }
+ job->bvec = bvec;
+ r = dm_io_async_bvec(1, &job->src, READ, job->bvec,
+ io_callback, job);
+ return r;
+ }
+
+ bvec = kmalloc((job->nr_pages + bio->bi_vcnt - bio->bi_idx)
+ * sizeof(*bvec), GFP_KERNEL);
+ if (!bvec) {
+ DMERR("do_fetch: No memory");
+ return 1;
+ }
+
+ i = 0;
+ while (head) {
+ bvec[i].bv_len = min(head, (unsigned int)PAGE_SIZE);
+ bvec[i].bv_offset = 0;
+ bvec[i].bv_page = pl->page;
+ head -= bvec[i].bv_len;
+ pl = pl->next;
+ i++;
+ }
+
+ remaining = bio->bi_size;
+ j = bio->bi_idx;
+ while (remaining) {
+ bvec[i] = bio->bi_io_vec[j];
+ remaining -= bvec[i].bv_len;
+ i++; j++;
+ }
+
+ if (tail) {
+ idx = i;
+ bvec[i].bv_offset = (to_bytes(offset) + bio->bi_size) &
+ (PAGE_SIZE - 1);
+ bvec[i].bv_len = PAGE_SIZE - bvec[i].bv_offset;
+ bvec[i].bv_page = pl->page;
+ tail -= bvec[i].bv_len;
+ pl = pl->next; i++;
+ while (tail) {
+ bvec[i].bv_len = PAGE_SIZE;
+ bvec[i].bv_offset = 0;
+ bvec[i].bv_page = pl->page;
+ tail -= bvec[i].bv_len;
+ pl = pl->next; i++;
+ }
+ }
+
+ job->bvec = bvec;
+ r = dm_io_async_bvec(1, &job->src, READ, job->bvec + idx,
+ io_callback, job);
+
+ return r;
+ }
+}
+
+/*
+ * Store data to the cache source device asynchronously.
+ * For a READ bio request, the data fetched from the source device are returned
+ * to kernel and stored in cache at the same time.
+ * For a WRITE bio request, the data are written to the cache and source device
+ * at the same time.
+ */
+static int do_store(struct kcached_job *job)
+{
+ int i, j, r = 0;
+ struct bio *bio = job->bio, *clone;
+ struct cache_c *dmc = job->dmc;
+ unsigned int offset, head, tail, remaining, nr_vecs;
+ struct bio_vec *bvec;
+
+ offset = (unsigned int) (bio->bi_sector & dmc->block_mask);
+ head = to_bytes(offset);
+ tail = to_bytes(dmc->block_size) - bio->bi_size - head;
+
+ DPRINTK("do_store: %llu(%llu->%llu,%llu), head:%u,tail:%u",
+ bio->bi_sector, job->src.sector, job->dest.sector,
+ job->src.count, head, tail);
+
+ /* A READ is acknowledged as soon as the requested data is fetched, and
+ does not have to wait for it being stored in cache. The bio is cloned
+ so that the original one can be ended here. But to avoid copying
+ pages, we reuse the pages allocated for the original bio, and mark
+ each of them to prevent the pages being freed before the cache
+ insertion is completed.
+ */
+ if (bio_data_dir(bio) == READ) {
+ clone = bio_clone(bio, GFP_NOIO);
+ for (i=bio->bi_idx; i<bio->bi_vcnt; i++) {
+ get_page(bio->bi_io_vec[i].bv_page);
+ }
+ DPRINTK("bio ended for %llu:%u", bio->bi_sector, bio->bi_size);
+ bio_endio(bio, 0);
+ bio = clone;
+ job->bio = clone;
+ }
+
+ if (0 == job->nr_pages) /* Original request is aligned with cache blocks */
+ r = dm_io_async_bvec(1, &job->dest, WRITE, bio->bi_io_vec + bio->bi_idx,
+ io_callback, job);
+ else {
+ if (bio_data_dir(bio) == WRITE && head > 0 && tail > 0) {
+ DPRINTK("Special case: %lu %u %u", bio_data_dir(bio), head, tail);
+ nr_vecs = job->nr_pages + bio->bi_vcnt - bio->bi_idx;
+ if (offset && (offset + bio->bi_size < PAGE_SIZE)) nr_vecs++;
+ DPRINTK("Create %u new vecs", nr_vecs);
+ bvec = kmalloc(nr_vecs * sizeof(*bvec), GFP_KERNEL);
+ if (!bvec) {
+ DMERR("do_store: No memory");
+ return 1;
+ }
+
+ i = 0;
+ while (head) {
+ bvec[i].bv_len = min(head, job->bvec[i].bv_len);
+ bvec[i].bv_offset = 0;
+ bvec[i].bv_page = job->bvec[i].bv_page;
+ head -= bvec[i].bv_len;
+ i++;
+ }
+ remaining = bio->bi_size;
+ j = bio->bi_idx;
+ while (remaining) {
+ bvec[i] = bio->bi_io_vec[j];
+ remaining -= bvec[i].bv_len;
+ i++; j++;
+ }
+ j = (to_bytes(offset) + bio->bi_size) / PAGE_SIZE;
+ bvec[i].bv_offset = (to_bytes(offset) + bio->bi_size) -
+ j * PAGE_SIZE;
+ bvec[i].bv_len = PAGE_SIZE - bvec[i].bv_offset;
+ bvec[i].bv_page = job->bvec[j].bv_page;
+ tail -= bvec[i].bv_len;
+ i++; j++;
+ while (tail) {
+ bvec[i] = job->bvec[j];
+ tail -= bvec[i].bv_len;
+ i++; j++;
+ }
+ kfree(job->bvec);
+ job->bvec = bvec;
+ }
+
+ r = dm_io_async_bvec(1, &job->dest, WRITE, job->bvec, io_callback, job);
+ }
+
+ return r;
+}
+
+static int do_io(struct kcached_job *job)
+{
+ int r = 0;
+
+ if (job->rw == READ) { /* Read from source device */
+ r = do_fetch(job);
+ } else { /* Write to cache device */
+ r = do_store(job);
+ }
+
+ return r;
+}
+
+static int do_pages(struct kcached_job *job)
+{
+ int r = 0;
+
+ r = kcached_get_pages(job->dmc, job->nr_pages, &job->pages);
+
+ if (r == -ENOMEM) /* can't complete now */
+ return 1;
+
+ /* this job is ready for io */
+ push(&_io_jobs, job);
+ return 0;
+}
+
+/*
+ * Flush the bios that are waiting for this cache insertion or write back.
+ */
+static void flush_bios(struct cacheblock *cacheblock)
+{
+ struct bio *bio;
+ struct bio *n;
+
+ spin_lock(&cacheblock->lock);
+ bio = bio_list_get(&cacheblock->bios);
+ if (is_state(cacheblock->state, WRITEBACK)) { /* Write back finished */
+ cacheblock->state = VALID;
+ } else { /* Cache insertion finished */
+ set_state(cacheblock->state, VALID);
+ clear_state(cacheblock->state, RESERVED);
+ }
+ spin_unlock(&cacheblock->lock);
+
+ while (bio) {
+ n = bio->bi_next;
+ bio->bi_next = NULL;
+ DPRINTK("Flush bio: %llu->%llu (%u bytes)",
+ cacheblock->block, bio->bi_sector, bio->bi_size);
+ generic_make_request(bio);
+ bio = n;
+ }
+}
+
+static int do_complete(struct kcached_job *job)
+{
+ int i, r = 0;
+ struct bio *bio = job->bio;
+
+ DPRINTK("do_complete: %llu", bio->bi_sector);
+
+ if (bio_data_dir(bio) == READ) {
+ for (i=bio->bi_idx; i<bio->bi_vcnt; i++) {
+ put_page(bio->bi_io_vec[i].bv_page);
+ }
+ bio_put(bio);
+ } else
+ bio_endio(bio, 0);
+
+ if (job->nr_pages > 0) {
+ kfree(job->bvec);
+ kcached_put_pages(job->dmc, job->pages);
+ }
+
+ flush_bios(job->cacheblock);
+ mempool_free(job, _job_pool);
+
+ if (atomic_dec_and_test(&job->dmc->nr_jobs))
+ wake_up(&job->dmc->destroyq);
+
+ return r;
+}
+
+/*
+ * Run through a list for as long as possible. Returns the count
+ * of successful jobs.
+ */
+static int process_jobs(struct list_head *jobs,
+ int (*fn) (struct kcached_job *))
+{
+ struct kcached_job *job;
+ int r, count = 0;
+
+ while ((job = pop(jobs))) {
+ r = fn(job);
+
+ if (r < 0) {
+ /* error this rogue job */
+ DMERR("process_jobs: Job processing error");
+ }
+
+ if (r > 0) {
+ /*
+ * We couldn't service this job ATM, so
+ * push this job back onto the list.
+ */
+ push(jobs, job);
+ break;
+ }
+
+ count++;
+ }
+
+ return count;
+}
+
+static void do_work(struct work_struct *ignored)
+{
+ process_jobs(&_complete_jobs, do_complete);
+ process_jobs(&_pages_jobs, do_pages);
+ process_jobs(&_io_jobs, do_io);
+}
+
+static void queue_job(struct kcached_job *job)
+{
+ atomic_inc(&job->dmc->nr_jobs);
+ if (job->nr_pages > 0) /* Request pages */
+ push(&_pages_jobs, job);
+ else /* Go ahead to do I/O */
+ push(&_io_jobs, job);
+ wake();
+}
+
+static int kcached_init(struct cache_c *dmc)
+{
+ int r;
+
+ spin_lock_init(&dmc->lock);
+ dmc->pages = NULL;
+ dmc->nr_pages = dmc->nr_free_pages = 0;
+ r = alloc_bio_pages(dmc, DMCACHE_COPY_PAGES);
+ if (r) {
+ DMERR("kcached_init: Could not allocate bio pages");
+ return r;
+ }
+
+ init_waitqueue_head(&dmc->destroyq);
+ atomic_set(&dmc->nr_jobs, 0);
+
+ return 0;
+}
+
+void kcached_client_destroy(struct cache_c *dmc)
+{
+ /* Wait for completion of all jobs submitted by this client. */
+ wait_event(dmc->destroyq, !atomic_read(&dmc->nr_jobs));
+
+ free_bio_pages(dmc);
+}
+
+
+/****************************************************************************
+ * Functions for writing back dirty blocks.
+ * We leverage kcopyd to write back dirty blocks because it is convenient to
+ * use and it is not reasonble to reimplement the same function here. But we
+ * need to reserve pages for both kcached and kcopyd. TODO: dynamically change
+ * the number of reserved pages.
+ ****************************************************************************/
+
+static void copy_callback(int read_err, unsigned int write_err, void *context)
+{
+ struct cacheblock *cacheblock = (struct cacheblock *) context;
+
+ flush_bios(cacheblock);
+}
+
+static void copy_block(struct cache_c *dmc, struct dm_io_region src,
+ struct dm_io_region dest, struct cacheblock *cacheblock)
+{
+ DPRINTK("Copying: %llu:%llu->%llu:%llu",
+ src.sector, src.count * 512, dest.sector, dest.count * 512);
+ dm_kcopyd_copy(dmc->kcp_client, &src, 1, &dest, 0, \
+ (dm_kcopyd_notify_fn) copy_callback, (void *)cacheblock);
+}
+
+static void write_back(struct cache_c *dmc, sector_t index, unsigned
int length)
+{
+ struct dm_io_region src, dest;
+ struct cacheblock *cacheblock = &dmc->cache[index];
+ unsigned int i;
+
+ DPRINTK("Write back block %llu(%llu, %u)",
+ index, cacheblock->block, length);
+ src.bdev = dmc->cache_dev->bdev;
+ src.sector = index << dmc->block_shift;
+ src.count = dmc->block_size * length;
+ dest.bdev = dmc->src_dev->bdev;
+ dest.sector = cacheblock->block;
+ dest.count = dmc->block_size * length;
+
+ for (i=0; i<length; i++)
+ set_state(dmc->cache[index+i].state, WRITEBACK);
+ dmc->dirty_blocks -= length;
+ copy_block(dmc, src, dest, cacheblock);
+}
+
+
+/****************************************************************************
+ * Functions for implementing the various cache operations.
+ ****************************************************************************/
+
+/*
+ * Map a block from the source device to a block in the cache device.
+ */
+static unsigned long hash_block(struct cache_c *dmc, sector_t block)
+{
+ unsigned long set_number, value;
+
+ value = (unsigned long)(block >> (dmc->block_shift +
+ dmc->consecutive_shift));
+ set_number = hash_long(value, dmc->bits) / dmc->assoc;
+
+ return set_number;
+}
+
+/*
+ * Reset the LRU counters (the cache's global counter and each cache block's
+ * counter). This seems to be a naive implementaion. However, consider the
+ * rareness of this event, it might be more efficient that other more complex
+ * schemes. TODO: a more elegant solution.
+ */
+static void cache_reset_counter(struct cache_c *dmc)
+{
+ sector_t i;
+ struct cacheblock *cache = dmc->cache;
+
+ DPRINTK("Reset LRU counters");
+ for (i=0; i<dmc->size; i++)
+ cache[i].counter = 0;
+
+ dmc->counter = 0;
+}
+
+/*
+ * Lookup a block in the cache.
+ *
+ * Return value:
+ * 1: cache hit (cache_block stores the index of the matched block)
+ * 0: cache miss but frame is allocated for insertion; cache_block stores the
+ * frame's index:
+ * If there are empty frames, then the first encounted is used.
+ * If there are clean frames, then the LRU clean block is replaced.
+ * 2: cache miss and frame is not allocated; cache_block stores the LRU dirty
+ * block's index:
+ * This happens when the entire set is dirty.
+ * -1: cache miss and no room for insertion:
+ * This happens when the entire set in transition modes (RESERVED or
+ * WRITEBACK).
+ *
+ */
+static int cache_lookup(struct cache_c *dmc, sector_t block,
+ sector_t *cache_block)
+{
+ unsigned long set_number = hash_block(dmc, block);
+ sector_t index;
+ int i, res;
+ unsigned int cache_assoc = dmc->assoc;
+ struct cacheblock *cache = dmc->cache;
+ int invalid = -1, oldest = -1, oldest_clean = -1;
+ unsigned long counter = ULONG_MAX, clean_counter = ULONG_MAX;
+
+ index=set_number * cache_assoc;
+
+ for (i=0; i<cache_assoc; i++, index++) {
+ if (is_state(cache[index].state, VALID) ||
+ is_state(cache[index].state, RESERVED)) {
+ if (cache[index].block == block) {
+ *cache_block = index;
+ /* Reset all counters if the largest one is going to overflow */
+ if (dmc->counter == ULONG_MAX) cache_reset_counter(dmc);
+ cache[index].counter = ++dmc->counter;
+ break;
+ } else {
+ /* Don't consider blocks that are in the middle of copying */
+ if (!is_state(cache[index].state, RESERVED) &&
+ !is_state(cache[index].state, WRITEBACK)) {
+ if (!is_state(cache[index].state, DIRTY) &&
+ cache[index].counter < clean_counter) {
+ clean_counter = cache[index].counter;
+ oldest_clean = i;
+ }
+ if (cache[index].counter < counter) {
+ counter = cache[index].counter;
+ oldest = i;
+ }
+ }
+ }
+ } else {
+ if (-1 == invalid) invalid = i;
+ }
+ }
+
+ res = i < cache_assoc ? 1 : 0;
+ if (!res) { /* Cache miss */
+ if (invalid != -1) /* Choose the first empty frame */
+ *cache_block = set_number * cache_assoc + invalid;
+ else if (oldest_clean != -1) /* Choose the LRU clean block to replace */
+ *cache_block = set_number * cache_assoc + oldest_clean;
+ else if (oldest != -1) { /* Choose the LRU dirty block to evict */
+ res = 2;
+ *cache_block = set_number * cache_assoc + oldest;
+ } else {
+ res = -1;
+ }
+ }
+
+ if (-1 == res)
+ DPRINTK("Cache lookup: Block %llu(%lu):%s",
+ block, set_number, "NO ROOM");
+ else
+ DPRINTK("Cache lookup: Block %llu(%lu):%llu(%s)",
+ block, set_number, *cache_block,
+ 1 == res ? "HIT" : (0 == res ? "MISS" : "WB NEEDED"));
+ return res;
+}
+
+/*
+ * Insert a block into the cache (in the frame specified by cache_block).
+ */
+static int cache_insert(struct cache_c *dmc, sector_t block,
+ sector_t cache_block)
+{
+ struct cacheblock *cache = dmc->cache;
+
+ /* Mark the block as RESERVED because although it is allocated, the data are
+ not in place until kcopyd finishes its job.
+ */
+ cache[cache_block].block = block;
+ cache[cache_block].state = RESERVED;
+ if (dmc->counter == ULONG_MAX) cache_reset_counter(dmc);
+ cache[cache_block].counter = ++dmc->counter;
+
+ return 1;
+}
+
+/*
+ * Invalidate a block (specified by cache_block) in the cache.
+ */
+static void cache_invalidate(struct cache_c *dmc, sector_t cache_block)
+{
+ struct cacheblock *cache = dmc->cache;
+
+ DPRINTK("Cache invalidate: Block %llu(%llu)",
+ cache_block, cache[cache_block].block);
+ clear_state(cache[cache_block].state, VALID);
+}
+
+/*
+ * Handle a cache hit:
+ * For READ, serve the request from cache is the block is ready; otherwise,
+ * queue the request for later processing.
+ * For write, invalidate the cache block if write-through. If write-back,
+ * serve the request from cache if the block is ready, or queue the request
+ * for later processing if otherwise.
+ */
+static int cache_hit(struct cache_c *dmc, struct bio* bio, sector_t
cache_block)
+{
+ unsigned int offset = (unsigned int)(bio->bi_sector & dmc->block_mask);
+ struct cacheblock *cache = dmc->cache;
+
+ dmc->cache_hits++;
+
+ if (bio_data_dir(bio) == READ) { /* READ hit */
+ bio->bi_bdev = dmc->cache_dev->bdev;
+ bio->bi_sector = (cache_block << dmc->block_shift) + offset;
+
+ spin_lock(&cache[cache_block].lock);
+
+ if (is_state(cache[cache_block].state, VALID)) { /* Valid cache block */
+ spin_unlock(&cache[cache_block].lock);
+ return 1;
+ }
+
+ /* Cache block is not ready yet */
+ DPRINTK("Add to bio list %s(%llu)",
+ dmc->cache_dev->name, bio->bi_sector);
+ bio_list_add(&cache[cache_block].bios, bio);
+
+ spin_unlock(&cache[cache_block].lock);
+ return 0;
+ } else { /* WRITE hit */
+ if (dmc->write_policy == WRITE_THROUGH) { /* Invalidate cached data */
+ cache_invalidate(dmc, cache_block);
+ bio->bi_bdev = dmc->src_dev->bdev;
+ return 1;
+ }
+
+ /* Write delay */
+ if (!is_state(cache[cache_block].state, DIRTY)) {
+ set_state(cache[cache_block].state, DIRTY);
+ dmc->dirty_blocks++;
+ }
+
+ spin_lock(&cache[cache_block].lock);
+
+ /* In the middle of write back */
+ if (is_state(cache[cache_block].state, WRITEBACK)) {
+ /* Delay this write until the block is written back */
+ bio->bi_bdev = dmc->src_dev->bdev;
+ DPRINTK("Add to bio list %s(%llu)",
+ dmc->src_dev->name, bio->bi_sector);
+ bio_list_add(&cache[cache_block].bios, bio);
+ spin_unlock(&cache[cache_block].lock);
+ return 0;
+ }
+
+ /* Cache block not ready yet */
+ if (is_state(cache[cache_block].state, RESERVED)) {
+ bio->bi_bdev = dmc->cache_dev->bdev;
+ bio->bi_sector = (cache_block << dmc->block_shift) + offset;
+ DPRINTK("Add to bio list %s(%llu)",
+ dmc->cache_dev->name, bio->bi_sector);
+ bio_list_add(&cache[cache_block].bios, bio);
+ spin_unlock(&cache[cache_block].lock);
+ return 0;
+ }
+
+ /* Serve the request from cache */
+ bio->bi_bdev = dmc->cache_dev->bdev;
+ bio->bi_sector = (cache_block << dmc->block_shift) + offset;
+
+ spin_unlock(&cache[cache_block].lock);
+ return 1;
+ }
+}
+
+static struct kcached_job *new_kcached_job(struct cache_c *dmc,
struct bio* bio,
+ sector_t request_block,
+ sector_t cache_block)
+{
+ struct dm_io_region src, dest;
+ struct kcached_job *job;
+
+ src.bdev = dmc->src_dev->bdev;
+ src.sector = request_block;
+ src.count = dmc->block_size;
+ dest.bdev = dmc->cache_dev->bdev;
+ dest.sector = cache_block << dmc->block_shift;
+ dest.count = src.count;
+
+ job = mempool_alloc(_job_pool, GFP_NOIO);
+ job->dmc = dmc;
+ job->bio = bio;
+ job->src = src;
+ job->dest = dest;
+ job->cacheblock = &dmc->cache[cache_block];
+
+ return job;
+}
+
+/*
+ * Handle a read cache miss:
+ * Update the metadata; fetch the necessary block from source device;
+ * store data to cache device.
+ */
+static int cache_read_miss(struct cache_c *dmc, struct bio* bio,
+ sector_t cache_block) {
+ struct cacheblock *cache = dmc->cache;
+ unsigned int offset, head, tail;
+ struct kcached_job *job;
+ sector_t request_block, left;
+
+ offset = (unsigned int)(bio->bi_sector & dmc->block_mask);
+ request_block = bio->bi_sector - offset;
+
+ if (cache[cache_block].state & VALID) {
+ DPRINTK("Replacing %llu->%llu",
+ cache[cache_block].block, request_block);
+ dmc->replace++;
+ } else DPRINTK("Insert block %llu at empty frame %llu",
+ request_block, cache_block);
+
+ cache_insert(dmc, request_block, cache_block); /* Update metadata first */
+
+ job = new_kcached_job(dmc, bio, request_block, cache_block);
+
+ head = to_bytes(offset);
+
+ left = (dmc->src_dev->bdev->bd_inode->i_size>>9) - request_block;
+ if (left < dmc->block_size) {
+ tail = to_bytes(left) - bio->bi_size - head;
+ job->src.count = left;
+ job->dest.count = left;
+ } else
+ tail = to_bytes(dmc->block_size) - bio->bi_size - head;
+
+ /* Requested block is aligned with a cache block */
+ if (0 == head && 0 == tail)
+ job->nr_pages= 0;
+ else /* Need new pages to store extra data */
+ job->nr_pages = dm_div_up(head, PAGE_SIZE) + dm_div_up(tail, PAGE_SIZE);
+ job->rw = READ; /* Fetch data from the source device */
+
+ DPRINTK("Queue job for %llu (need %u pages)",
+ bio->bi_sector, job->nr_pages);
+ queue_job(job);
+
+ return 0;
+}
+
+/*
+ * Handle a write cache miss:
+ * If write-through, forward the request to source device.
+ * If write-back, update the metadata; fetch the necessary block from source
+ * device; write to cache device.
+ */
+static int cache_write_miss(struct cache_c *dmc, struct bio* bio,
sector_t cache_block) {
+ struct cacheblock *cache = dmc->cache;
+ unsigned int offset, head, tail;
+ struct kcached_job *job;
+ sector_t request_block, left;
+
+ if (dmc->write_policy == WRITE_THROUGH) { /* Forward request to souuce */
+ bio->bi_bdev = dmc->src_dev->bdev;
+ return 1;
+ }
+
+ offset = (unsigned int)(bio->bi_sector & dmc->block_mask);
+ request_block = bio->bi_sector - offset;
+
+ if (cache[cache_block].state & VALID) {
+ DPRINTK("Replacing %llu->%llu",
+ cache[cache_block].block, request_block);
+ dmc->replace++;
+ } else DPRINTK("Insert block %llu at empty frame %llu",
+ request_block, cache_block);
+
+ /* Write delay */
+ cache_insert(dmc, request_block, cache_block); /* Update metadata first */
+ set_state(cache[cache_block].state, DIRTY);
+ dmc->dirty_blocks++;
+
+ job = new_kcached_job(dmc, bio, request_block, cache_block);
+
+ head = to_bytes(offset);
+ left = (dmc->src_dev->bdev->bd_inode->i_size>>9) - request_block;
+ if (left < dmc->block_size) {
+ tail = to_bytes(left) - bio->bi_size - head;
+ job->src.count = left;
+ job->dest.count = left;
+ } else
+ tail = to_bytes(dmc->block_size) - bio->bi_size - head;
+
+ if (0 == head && 0 == tail) { /* Requested is aligned with a cache block */
+ job->nr_pages = 0;
+ job->rw = WRITE;
+ } else if (head && tail){ /* Special case: need to pad both head and tail */
+ job->nr_pages = dm_div_up(to_bytes(job->src.count), PAGE_SIZE);
+ job->rw = READ;
+ } else {
+ if (head) { /* Fetch only head */
+ job->src.count = to_sector(head);
+ job->nr_pages = dm_div_up(head, PAGE_SIZE);
+ } else { /* Fetch only tail */
+ job->src.sector = bio->bi_sector + to_sector(bio->bi_size);
+ job->src.count = to_sector(tail);
+ job->nr_pages = dm_div_up(tail, PAGE_SIZE);
+ }
+ job->rw = READ;
+ }
+
+ queue_job(job);
+
+ return 0;
+}
+
+/* Handle cache misses */
+static int cache_miss(struct cache_c *dmc, struct bio* bio, sector_t
cache_block) {
+ if (bio_data_dir(bio) == READ)
+ return cache_read_miss(dmc, bio, cache_block);
+ else
+ return cache_write_miss(dmc, bio, cache_block);
+}
+
+
+/****************************************************************************
+ * Functions for implementing the operations on a cache mapping.
+ ****************************************************************************/
+
+/*
+ * Decide the mapping and perform necessary cache operations for a bio request.
+ */
+static int cache_map(struct dm_target *ti, struct bio *bio,
+ union map_info *map_context)
+{
+ struct cache_c *dmc = (struct cache_c *) ti->private;
+ sector_t request_block, cache_block = 0, offset;
+ int res;
+
+ offset = bio->bi_sector & dmc->block_mask;
+ request_block = bio->bi_sector - offset;
+
+ DPRINTK("Got a %s for %llu ((%llu:%llu), %u bytes)",
+ bio_rw(bio) == WRITE ? "WRITE" : (bio_rw(bio) == READ ?
+ "READ":"READA"), bio->bi_sector, request_block, offset,
+ bio->bi_size);
+
+ if (bio_data_dir(bio) == READ) dmc->reads++;
+ else dmc->writes++;
+
+ res = cache_lookup(dmc, request_block, &cache_block);
+ if (1 == res) /* Cache hit; server request from cache */
+ return cache_hit(dmc, bio, cache_block);
+ else if (0 == res) /* Cache miss; replacement block is found */
+ return cache_miss(dmc, bio, cache_block);
+ else if (2 == res) { /* Entire cache set is dirty; initiate a write-back */
+ write_back(dmc, cache_block, 1);
+ dmc->writeback++;
+ }
+
+ /* Forward to source device */
+ bio->bi_bdev = dmc->src_dev->bdev;
+
+ return 1;
+}
+
+struct meta_dmc {
+ sector_t size;
+ unsigned int block_size;
+ unsigned int assoc;
+ unsigned int write_policy;
+ unsigned int chksum;
+};
+
+/* Load metadata stored by previous session from disk. */
+static int load_metadata(struct cache_c *dmc) {
+ struct dm_io_region where;
+ unsigned long bits;
+ sector_t dev_size = dmc->cache_dev->bdev->bd_inode->i_size >> 9;
+ sector_t meta_size, *meta_data, i, j, index = 0, limit, order;
+ struct meta_dmc *meta_dmc;
+ unsigned int chksum = 0, chksum_sav, consecutive_blocks;
+
+ meta_dmc = (struct meta_dmc *)vmalloc(512);
+ if (!meta_dmc) {
+ DMERR("load_metadata: Unable to allocate memory");
+ return 1;
+ }
+
+ where.bdev = dmc->cache_dev->bdev;
+ where.sector = dev_size - 1;
+ where.count = 1;
+ dm_io_sync_vm(1, &where, READ, meta_dmc, &bits, dmc);
+ DPRINTK("Loaded cache conf: block size(%u), cache size(%llu), " \
+ "associativity(%u), write policy(%u), chksum(%u)",
+ meta_dmc->block_size, meta_dmc->size,
+ meta_dmc->assoc, meta_dmc->write_policy,
+ meta_dmc->chksum);
+
+ dmc->block_size = meta_dmc->block_size;
+ dmc->block_shift = ffs(dmc->block_size) - 1;
+ dmc->block_mask = dmc->block_size - 1;
+
+ dmc->size = meta_dmc->size;
+ dmc->bits = ffs(dmc->size) - 1;
+
+ dmc->assoc = meta_dmc->assoc;
+ consecutive_blocks = dmc->assoc < CONSECUTIVE_BLOCKS ?
+ dmc->assoc : CONSECUTIVE_BLOCKS;
+ dmc->consecutive_shift = ffs(consecutive_blocks) - 1;
+
+ dmc->write_policy = meta_dmc->write_policy;
+ chksum_sav = meta_dmc->chksum;
+
+ vfree((void *)meta_dmc);
+
+
+ order = dmc->size * sizeof(struct cacheblock);
+ DMINFO("Allocate %lluKB (%luB per) mem for %llu-entry cache" \
+ "(capacity:%lluMB, associativity:%u, block size:%u " \
+ "sectors(%uKB), %s)",
+ (unsigned long long) order >> 10, (unsigned long)
sizeof(struct cacheblock),
+ (unsigned long long) dmc->size,
+ (unsigned long long) dmc->size * dmc->block_size >> (20-SECTOR_SHIFT),
+ dmc->assoc, dmc->block_size,
+ dmc->block_size >> (10-SECTOR_SHIFT),
+ dmc->write_policy ? "write-back" : "write-through");
+ dmc->cache = (struct cacheblock *)vmalloc(order);
+ if (!dmc->cache) {
+ DMERR("load_metadata: Unable to allocate memory");
+ return 1;
+ }
+
+ meta_size = dm_div_up(dmc->size * sizeof(sector_t), 512);
+ /* When requesting a new bio, the number of requested bvecs has to be
+ less than BIO_MAX_PAGES. Otherwise, null is returned. In dm-io.c,
+ this return value is not checked and kernel Oops may happen. We set
+ the limit here to avoid such situations. (2 additional bvecs are
+ required by dm-io for bookeeping.)
+ */
+ limit = (BIO_MAX_PAGES - 2) * (PAGE_SIZE >> SECTOR_SHIFT);
+ meta_data = (sector_t *)vmalloc(to_bytes(min(meta_size, limit)));
+ if (!meta_data) {
+ DMERR("load_metadata: Unable to allocate memory");
+ vfree((void *)dmc->cache);
+ return 1;
+ }
+
+ while(index < meta_size) {
+ where.sector = dev_size - 1 - meta_size + index;
+ where.count = min(meta_size - index, limit);
+ dm_io_sync_vm(1, &where, READ, meta_data, &bits, dmc);
+
+ for (i=to_bytes(index)/sizeof(sector_t), j=0;
+ j<to_bytes(where.count)/sizeof(sector_t) && i<dmc->size;
+ i++, j++) {
+ if(meta_data[j]) {
+ dmc->cache[i].block = meta_data[j];
+ dmc->cache[i].state = 1;
+ } else
+ dmc->cache[i].state = 0;
+ }
+ chksum = csum_partial((char *)meta_data, to_bytes(where.count), chksum);
+ index += where.count;
+ }
+
+ vfree((void *)meta_data);
+
+ if (chksum != chksum_sav) { /* Check the checksum of the metadata */
+ DPRINTK("Cache metadata loaded from disk is corrupted");
+ vfree((void *)dmc->cache);
+ return 1;
+ }
+
+ DMINFO("Cache metadata loaded from disk (offset %llu)",
+ (unsigned long long) dev_size - 1 - (unsigned long long) meta_size);;
+
+ return 0;
+}
+
+/* Store metadata onto disk. */
+static int dump_metadata(struct cache_c *dmc) {
+ struct dm_io_region where;
+ unsigned long bits;
+ sector_t dev_size = dmc->cache_dev->bdev->bd_inode->i_size >> 9;
+ sector_t meta_size, i, j, index = 0, limit, *meta_data;
+ struct meta_dmc *meta_dmc;
+ unsigned int chksum = 0;
+
+ meta_size = dm_div_up(dmc->size * sizeof(sector_t), 512);
+ limit = (BIO_MAX_PAGES - 2) * (PAGE_SIZE >> SECTOR_SHIFT);
+ meta_data = (sector_t *)vmalloc(to_bytes(min(meta_size, limit)));
+ if (!meta_data) {
+ DMERR("dump_metadata: Unable to allocate memory");
+ return 1;
+ }
+
+ where.bdev = dmc->cache_dev->bdev;
+ while(index < meta_size) {
+ where.sector = dev_size - 1 - meta_size + index;
+ where.count = min(meta_size - index, limit);
+
+ for (i=to_bytes(index)/sizeof(sector_t), j=0;
+ j<to_bytes(where.count)/sizeof(sector_t) && i<dmc->size;
+ i++, j++) {
+ /* Assume all invalid cache blocks store 0. We lose the block that
+ * is actually mapped to offset 0.
+ */
+ meta_data[j] = dmc->cache[i].state ? dmc->cache[i].block : 0;
+ }
+ chksum = csum_partial((char *)meta_data, to_bytes(where.count), chksum);
+
+ dm_io_sync_vm(1, &where, WRITE, meta_data, &bits, dmc);
+ index += where.count;
+ }
+
+ vfree((void *)meta_data);
+
+ meta_dmc = (struct meta_dmc *)vmalloc(512);
+ if (!meta_dmc) {
+ DMERR("dump_metadata: Unable to allocate memory");
+ return 1;
+ }
+
+ meta_dmc->block_size = dmc->block_size;
+ meta_dmc->size = dmc->size;
+ meta_dmc->assoc = dmc->assoc;
+ meta_dmc->write_policy = dmc->write_policy;
+ meta_dmc->chksum = chksum;
+
+ DPRINTK("Store metadata to disk: block size(%u), cache size(%llu), " \
+ "associativity(%u), write policy(%u), checksum(%u)",
+ meta_dmc->block_size, (unsigned long long) meta_dmc->size,
+ meta_dmc->assoc, meta_dmc->write_policy,
+ meta_dmc->chksum);
+
+ where.sector = dev_size - 1;
+ where.count = 1;
+ dm_io_sync_vm(1, &where, WRITE, meta_dmc, &bits, dmc);
+
+ vfree((void *)meta_dmc);
+
+ DMINFO("Cache metadata saved to disk (offset %llu)",
+ (unsigned long long) dev_size - 1 - (unsigned long long) meta_size);
+
+ return 0;
+}
+
+/*
+ * Construct a cache mapping.
+ * arg[0]: path to source device
+ * arg[1]: path to cache device
+ * arg[2]: cache persistence (if set, cache conf is loaded from disk)
+ * Cache configuration parameters (if not set, default values are used.
+ * arg[3]: cache block size (in sectors)
+ * arg[4]: cache size (in blocks)
+ * arg[5]: cache associativity
+ * arg[6]: write caching policy
+ */
+static int cache_ctr(struct dm_target *ti, unsigned int argc, char **argv)
+{
+ struct cache_c *dmc;
+ unsigned int consecutive_blocks, persistence = 0;
+ sector_t localsize, i, order;
+ sector_t data_size, meta_size, dev_size;
+ unsigned long long cache_size;
+ int r = -EINVAL;
+
+ if (argc < 2) {
+ ti->error = "dm-cache: Need at least 2 arguments (src dev and cache dev)";
+ goto bad;
+ }
+
+ dmc = kmalloc(sizeof(*dmc), GFP_KERNEL);
+ if (dmc == NULL) {
+ ti->error = "dm-cache: Failed to allocate cache context";
+ r = ENOMEM;
+ goto bad;
+ }
+
+ r = dm_get_device(ti, argv[0],
+ dm_table_get_mode(ti->table), &dmc->src_dev);
+ if (r) {
+ ti->error = "dm-cache: Source device lookup failed";
+ goto bad1;
+ }
+
+ r = dm_get_device(ti, argv[1],
+ dm_table_get_mode(ti->table), &dmc->cache_dev);
+ if (r) {
+ ti->error = "dm-cache: Cache device lookup failed";
+ goto bad2;
+ }
+
+ dmc->io_client = dm_io_client_create(DMCACHE_COPY_PAGES);
+ if (IS_ERR(dmc->io_client)) {
+ r = PTR_ERR(dmc->io_client);
+ ti->error = "Failed to create io client\n";
+ goto bad3;
+ }
+
+ r = dm_kcopyd_client_create(DMCACHE_COPY_PAGES, &dmc->kcp_client);
+ if (r) {
+ ti->error = "Failed to initialize kcopyd client\n";
+ goto bad4;
+ }
+
+ r = kcached_init(dmc);
+ if (r) {
+ ti->error = "Failed to initialize kcached";
+ goto bad5;
+ }
+
+ if (argc >= 3) {
+ if (sscanf(argv[2], "%u", &persistence) != 1) {
+ ti->error = "dm-cache: Invalid cache persistence";
+ r = -EINVAL;
+ goto bad6;
+ }
+ }
+ if (1 == persistence) {
+ if (load_metadata(dmc)) {
+ ti->error = "dm-cache: Invalid cache configuration";
+ r = -EINVAL;
+ goto bad6;
+ }
+ goto init; /* Skip reading cache parameters from command line */
+ } else if (persistence != 0) {
+ ti->error = "dm-cache: Invalid cache persistence";
+ r = -EINVAL;
+ goto bad6;
+ }
+
+ if (argc >= 4) {
+ if (sscanf(argv[3], "%u", &dmc->block_size) != 1) {
+ ti->error = "dm-cache: Invalid block size";
+ r = -EINVAL;
+ goto bad6;
+ }
+ if (!dmc->block_size || (dmc->block_size & (dmc->block_size - 1))) {
+ ti->error = "dm-cache: Invalid block size";
+ r = -EINVAL;
+ goto bad6;
+ }
+ } else
+ dmc->block_size = DEFAULT_BLOCK_SIZE;
+ dmc->block_shift = ffs(dmc->block_size) - 1;
+ dmc->block_mask = dmc->block_size - 1;
+
+ if (argc >= 5) {
+ if (sscanf(argv[4], "%llu", &cache_size) != 1) {
+ ti->error = "dm-cache: Invalid cache size";
+ r = -EINVAL;
+ goto bad6;
+ }
+ dmc->size = (sector_t) cache_size;
+ if (!dmc->size || (dmc->size & (dmc->size - 1))) {
+ ti->error = "dm-cache: Invalid cache size";
+ r = -EINVAL;
+ goto bad6;
+ }
+ } else
+ dmc->size = DEFAULT_CACHE_SIZE;
+ localsize = dmc->size;
+ dmc->bits = ffs(dmc->size) - 1;
+
+ if (argc >= 6) {
+ if (sscanf(argv[5], "%u", &dmc->assoc) != 1) {
+ ti->error = "dm-cache: Invalid cache associativity";
+ r = -EINVAL;
+ goto bad6;
+ }
+ if (!dmc->assoc || (dmc->assoc & (dmc->assoc - 1)) ||
+ dmc->size < dmc->assoc) {
+ ti->error = "dm-cache: Invalid cache associativity";
+ r = -EINVAL;
+ goto bad6;
+ }
+ } else
+ dmc->assoc = DEFAULT_CACHE_ASSOC;
+
+ DMINFO("%lld", dmc->cache_dev->bdev->bd_inode->i_size);
+ dev_size = dmc->cache_dev->bdev->bd_inode->i_size >> 9;
+ data_size = dmc->size * dmc->block_size;
+ meta_size = dm_div_up(dmc->size * sizeof(sector_t), 512) + 1;
+ if ((data_size + meta_size) > dev_size) {
+ DMERR("Requested cache size exeeds the cache device's capacity" \
+ "(%llu+%llu>%llu)",
+ (unsigned long long) data_size, (unsigned long long) meta_size,
+ (unsigned long long) dev_size);
+ ti->error = "dm-cache: Invalid cache size";
+ r = -EINVAL;
+ goto bad6;
+ }
+ consecutive_blocks = dmc->assoc < CONSECUTIVE_BLOCKS ?
+ dmc->assoc : CONSECUTIVE_BLOCKS;
+ dmc->consecutive_shift = ffs(consecutive_blocks) - 1;
+
+ if (argc >= 7) {
+ if (sscanf(argv[6], "%u", &dmc->write_policy) != 1) {
+ ti->error = "dm-cache: Invalid cache write policy";
+ r = -EINVAL;
+ goto bad6;
+ }
+ if (dmc->write_policy != 0 && dmc->write_policy != 1) {
+ ti->error = "dm-cache: Invalid cache write policy";
+ r = -EINVAL;
+ goto bad6;
+ }
+ } else
+ dmc->write_policy = DEFAULT_WRITE_POLICY;
+
+ order = dmc->size * sizeof(struct cacheblock);
+ localsize = data_size >> 11;
+ DMINFO("Allocate %lluKB (%luB per) mem for %llu-entry cache" \
+ "(capacity:%lluMB, associativity:%u, block size:%u " \
+ "sectors(%uKB), %s)",
+ (unsigned long long) order >> 10, (unsigned long)
sizeof(struct cacheblock),
+ (unsigned long long) dmc->size,
+ (unsigned long long) data_size >> (20-SECTOR_SHIFT),
+ dmc->assoc, dmc->block_size,
+ dmc->block_size >> (10-SECTOR_SHIFT),
+ dmc->write_policy ? "write-back" : "write-through");
+
+ dmc->cache = (struct cacheblock *)vmalloc(order);
+ if (!dmc->cache) {
+ ti->error = "Unable to allocate memory";
+ r = -ENOMEM;
+ goto bad6;
+ }
+
+init: /* Initialize the cache structs */
+ for (i=0; i<dmc->size; i++) {
+ bio_list_init(&dmc->cache[i].bios);
+ if(!persistence) dmc->cache[i].state = 0;
+ dmc->cache[i].counter = 0;
+ spin_lock_init(&dmc->cache[i].lock);
+ }
+
+ dmc->counter = 0;
+ dmc->dirty_blocks = 0;
+ dmc->reads = 0;
+ dmc->writes = 0;
+ dmc->cache_hits = 0;
+ dmc->replace = 0;
+ dmc->writeback = 0;
+ dmc->dirty = 0;
+
+ ti->split_io = dmc->block_size;
+ ti->private = dmc;
+ return 0;
+
+bad6:
+ kcached_client_destroy(dmc);
+bad5:
+ dm_kcopyd_client_destroy(dmc->kcp_client);
+bad4:
+ dm_io_client_destroy(dmc->io_client);
+bad3:
+ dm_put_device(ti, dmc->cache_dev);
+bad2:
+ dm_put_device(ti, dmc->src_dev);
+bad1:
+ kfree(dmc);
+bad:
+ return r;
+}
+
+
+static void cache_flush(struct cache_c *dmc)
+{
+ struct cacheblock *cache = dmc->cache;
+ sector_t i = 0;
+ unsigned int j;
+
+ DMINFO("Flush dirty blocks (%llu) ...", (unsigned long long)
dmc->dirty_blocks);
+ while (i< dmc->size) {
+ j = 1;
+ if (is_state(cache[i].state, DIRTY)) {
+ while ((i+j) < dmc->size && is_state(cache[i+j].state, DIRTY)
+ && (cache[i+j].block == cache[i].block + j *
+ dmc->block_size)) {
+ j++;
+ }
+ dmc->dirty += j;
+ write_back(dmc, i, j);
+ }
+ i += j;
+ }
+}
+
+/*
+ * Destroy the cache mapping.
+ */
+static void cache_dtr(struct dm_target *ti)
+{
+ struct cache_c *dmc = (struct cache_c *) ti->private;
+
+ if (dmc->dirty_blocks > 0) cache_flush(dmc);
+
+ kcached_client_destroy(dmc);
+
+ dm_kcopyd_client_destroy(dmc->kcp_client);
+
+ if (dmc->reads + dmc->writes > 0)
+ DMINFO("stats: reads(%lu), writes(%lu), cache hits(%lu, 0.%lu)," \
+ "replacement(%lu), replaced dirty blocks(%lu), " \
+ "flushed dirty blocks(%lu)",
+ dmc->reads, dmc->writes, dmc->cache_hits,
+ dmc->cache_hits * 100 / (dmc->reads + dmc->writes),
+ dmc->replace, dmc->writeback, dmc->dirty);
+
+ dump_metadata(dmc); /* Always dump metadata to disk before exit */
+ vfree((void *)dmc->cache);
+ dm_io_client_destroy(dmc->io_client);
+
+ dm_put_device(ti, dmc->src_dev);
+ dm_put_device(ti, dmc->cache_dev);
+ kfree(dmc);
+}
+
+/*
+ * Report cache status:
+ * Output cache stats upon request of device status;
+ * Output cache configuration upon request of table status.
+ */
+static int cache_status(struct dm_target *ti, status_type_t type,
+ char *result, unsigned int maxlen)
+{
+ struct cache_c *dmc = (struct cache_c *) ti->private;
+ int sz = 0;
+
+ switch (type) {
+ case STATUSTYPE_INFO:
+ DMEMIT("stats: reads(%lu), writes(%lu), cache hits(%lu, 0.%lu)," \
+ "replacement(%lu), replaced dirty blocks(%lu)",
+ dmc->reads, dmc->writes, dmc->cache_hits,
+ (dmc->reads + dmc->writes) > 0 ? \
+ dmc->cache_hits * 100 / (dmc->reads + dmc->writes) : 0,
+ dmc->replace, dmc->writeback);
+ break;
+ case STATUSTYPE_TABLE:
+ DMEMIT("conf: capacity(%lluM), associativity(%u), block size(%uK), %s",
+ (unsigned long long) dmc->size * dmc->block_size >> 11,
+ dmc->assoc, dmc->block_size>>(10-SECTOR_SHIFT),
+ dmc->write_policy ? "write-back":"write-through");
+ break;
+ }
+ return 0;
+}
+
+
+/****************************************************************************
+ * Functions for manipulating a cache target.
+ ****************************************************************************/
+
+static struct target_type cache_target = {
+ .name = "cache",
+ .version= {1, 0, 1},
+ .module = THIS_MODULE,
+ .ctr = cache_ctr,
+ .dtr = cache_dtr,
+ .map = cache_map,
+ .status = cache_status,
+};
+
+/*
+ * Initiate a cache target.
+ */
+int __init dm_cache_init(void)
+{
+ int r;
+
+ r = jobs_init();
+ if (r)
+ return r;
+
+ _kcached_wq = create_singlethread_workqueue("kcached");
+ if (!_kcached_wq) {
+ DMERR("failed to start kcached");
+ return -ENOMEM;
+ }
+ INIT_WORK(&_kcached_work, do_work);
+
+ r = dm_register_target(&cache_target);
+ if (r < 0) {
+ DMERR("cache: register failed %d", r);
+ destroy_workqueue(_kcached_wq);
+ }
+
+ return r;
+}
+
+/*
+ * Destroy a cache target.
+ */
+static void __exit dm_cache_exit(void)
+{
+ dm_unregister_target(&cache_target);
+
+ jobs_exit();
+ destroy_workqueue(_kcached_wq);
+}
+
+module_init(dm_cache_init);
+module_exit(dm_cache_exit);
+
+MODULE_DESCRIPTION(DM_NAME " cache target");
+MODULE_AUTHOR("Ming Zhao <mingzhao99th@...il.com>");
+MODULE_LICENSE("GPL");
diff -Naur linux-2.6.39.1/drivers/md/Kconfig
linux-2.6.39.1-dm-cache/drivers/md/Kconfig
--- linux-2.6.39.1/drivers/md/Kconfig 2011-06-03 00:34:20.000000000 +0000
+++ linux-2.6.39.1-dm-cache/drivers/md/Kconfig 2011-10-17
19:48:10.000000000 +0000
@@ -333,4 +333,10 @@
---help---
A target that intermittently fails I/O for debugging purposes.
+config DM_CACHE
+ tristate "Cache target support (EXPERIMENTAL)"
+ depends on BLK_DEV_DM && EXPERIMENTAL
+ ---help---
+ Support for generic cache target for device-mapper.
+
endif # MD
diff -Naur linux-2.6.39.1/drivers/md/Makefile
linux-2.6.39.1-dm-cache/drivers/md/Makefile
--- linux-2.6.39.1/drivers/md/Makefile 2011-06-03 00:34:20.000000000 +0000
+++ linux-2.6.39.1-dm-cache/drivers/md/Makefile 2011-10-17
19:01:29.000000000 +0000
@@ -37,6 +37,7 @@
obj-$(CONFIG_DM_MIRROR) += dm-mirror.o dm-log.o dm-region-hash.o
obj-$(CONFIG_DM_LOG_USERSPACE) += dm-log-userspace.o
obj-$(CONFIG_DM_ZERO) += dm-zero.o
+obj-$(CONFIG_DM_CACHE) += dm-cache.o
obj-$(CONFIG_DM_RAID) += dm-raid.o
ifeq ($(CONFIG_DM_UEVENT),y)
--
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