md/r5cache: improve recovery with read ahead page pool
authorSong Liu <songliubraving@fb.com>
Wed, 8 Mar 2017 00:49:17 +0000 (16:49 -0800)
committerShaohua Li <shli@fb.com>
Thu, 16 Mar 2017 23:55:53 +0000 (16:55 -0700)
In r5cache recovery, the journal device is scanned page by page.
Currently, we use sync_page_io() to read journal device. This is
not efficient when we have to recovery many stripes from the journal.

To improve the speed of recovery, this patch introduces a read ahead
page pool (ra_pool) to recovery_ctx. With ra_pool, multiple consecutive
pages are read in one IO. Then the recovery code read the journal from
ra_pool.

With ra_pool, r5l_recovery_ctx has become much bigger. Therefore,
r5l_recovery_log() is refactored so r5l_recovery_ctx is not using
stack space.

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>
drivers/md/raid5-cache.c

index 738e180d3740a7766ef12fe8c9c8fbc7d0f72c00..5c8640c86b90eb487ead2c65a1781f09a3a1b2ef 100644 (file)
@@ -30,6 +30,7 @@
  * underneath hardware sector size. only works with PAGE_SIZE == 4096
  */
 #define BLOCK_SECTORS (8)
+#define BLOCK_SECTOR_SHIFT (3)
 
 /*
  * log->max_free_space is min(1/4 disk size, 10G reclaimable space).
@@ -1552,6 +1553,8 @@ bool r5l_log_disk_error(struct r5conf *conf)
        return ret;
 }
 
+#define R5L_RECOVERY_PAGE_POOL_SIZE 256
+
 struct r5l_recovery_ctx {
        struct page *meta_page;         /* current meta */
        sector_t meta_total_blocks;     /* total size of current meta and data */
@@ -1560,18 +1563,131 @@ struct r5l_recovery_ctx {
        int data_parity_stripes;        /* number of data_parity stripes */
        int data_only_stripes;          /* number of data_only stripes */
        struct list_head cached_list;
+
+       /*
+        * read ahead page pool (ra_pool)
+        * in recovery, log is read sequentially. It is not efficient to
+        * read every page with sync_page_io(). The read ahead page pool
+        * reads multiple pages with one IO, so further log read can
+        * just copy data from the pool.
+        */
+       struct page *ra_pool[R5L_RECOVERY_PAGE_POOL_SIZE];
+       sector_t pool_offset;   /* offset of first page in the pool */
+       int total_pages;        /* total allocated pages */
+       int valid_pages;        /* pages with valid data */
+       struct bio *ra_bio;     /* bio to do the read ahead */
 };
 
+static int r5l_recovery_allocate_ra_pool(struct r5l_log *log,
+                                           struct r5l_recovery_ctx *ctx)
+{
+       struct page *page;
+
+       ctx->ra_bio = bio_alloc_bioset(GFP_KERNEL, BIO_MAX_PAGES, log->bs);
+       if (!ctx->ra_bio)
+               return -ENOMEM;
+
+       ctx->valid_pages = 0;
+       ctx->total_pages = 0;
+       while (ctx->total_pages < R5L_RECOVERY_PAGE_POOL_SIZE) {
+               page = alloc_page(GFP_KERNEL);
+
+               if (!page)
+                       break;
+               ctx->ra_pool[ctx->total_pages] = page;
+               ctx->total_pages += 1;
+       }
+
+       if (ctx->total_pages == 0) {
+               bio_put(ctx->ra_bio);
+               return -ENOMEM;
+       }
+
+       ctx->pool_offset = 0;
+       return 0;
+}
+
+static void r5l_recovery_free_ra_pool(struct r5l_log *log,
+                                       struct r5l_recovery_ctx *ctx)
+{
+       int i;
+
+       for (i = 0; i < ctx->total_pages; ++i)
+               put_page(ctx->ra_pool[i]);
+       bio_put(ctx->ra_bio);
+}
+
+/*
+ * fetch ctx->valid_pages pages from offset
+ * In normal cases, ctx->valid_pages == ctx->total_pages after the call.
+ * However, if the offset is close to the end of the journal device,
+ * ctx->valid_pages could be smaller than ctx->total_pages
+ */
+static int r5l_recovery_fetch_ra_pool(struct r5l_log *log,
+                                     struct r5l_recovery_ctx *ctx,
+                                     sector_t offset)
+{
+       bio_reset(ctx->ra_bio);
+       ctx->ra_bio->bi_bdev = log->rdev->bdev;
+       bio_set_op_attrs(ctx->ra_bio, REQ_OP_READ, 0);
+       ctx->ra_bio->bi_iter.bi_sector = log->rdev->data_offset + offset;
+
+       ctx->valid_pages = 0;
+       ctx->pool_offset = offset;
+
+       while (ctx->valid_pages < ctx->total_pages) {
+               bio_add_page(ctx->ra_bio,
+                            ctx->ra_pool[ctx->valid_pages], PAGE_SIZE, 0);
+               ctx->valid_pages += 1;
+
+               offset = r5l_ring_add(log, offset, BLOCK_SECTORS);
+
+               if (offset == 0)  /* reached end of the device */
+                       break;
+       }
+
+       return submit_bio_wait(ctx->ra_bio);
+}
+
+/*
+ * try read a page from the read ahead page pool, if the page is not in the
+ * pool, call r5l_recovery_fetch_ra_pool
+ */
+static int r5l_recovery_read_page(struct r5l_log *log,
+                                 struct r5l_recovery_ctx *ctx,
+                                 struct page *page,
+                                 sector_t offset)
+{
+       int ret;
+
+       if (offset < ctx->pool_offset ||
+           offset >= ctx->pool_offset + ctx->valid_pages * BLOCK_SECTORS) {
+               ret = r5l_recovery_fetch_ra_pool(log, ctx, offset);
+               if (ret)
+                       return ret;
+       }
+
+       BUG_ON(offset < ctx->pool_offset ||
+              offset >= ctx->pool_offset + ctx->valid_pages * BLOCK_SECTORS);
+
+       memcpy(page_address(page),
+              page_address(ctx->ra_pool[(offset - ctx->pool_offset) >>
+                                        BLOCK_SECTOR_SHIFT]),
+              PAGE_SIZE);
+       return 0;
+}
+
 static int r5l_recovery_read_meta_block(struct r5l_log *log,
                                        struct r5l_recovery_ctx *ctx)
 {
        struct page *page = ctx->meta_page;
        struct r5l_meta_block *mb;
        u32 crc, stored_crc;
+       int ret;
 
-       if (!sync_page_io(log->rdev, ctx->pos, PAGE_SIZE, page, REQ_OP_READ, 0,
-                         false))
-               return -EIO;
+       ret = r5l_recovery_read_page(log, ctx, page, ctx->pos);
+       if (ret != 0)
+               return ret;
 
        mb = page_address(page);
        stored_crc = le32_to_cpu(mb->checksum);
@@ -1653,8 +1769,7 @@ static void r5l_recovery_load_data(struct r5l_log *log,
        raid5_compute_sector(conf,
                             le64_to_cpu(payload->location), 0,
                             &dd_idx, sh);
-       sync_page_io(log->rdev, log_offset, PAGE_SIZE,
-                    sh->dev[dd_idx].page, REQ_OP_READ, 0, false);
+       r5l_recovery_read_page(log, ctx, sh->dev[dd_idx].page, log_offset);
        sh->dev[dd_idx].log_checksum =
                le32_to_cpu(payload->checksum[0]);
        ctx->meta_total_blocks += BLOCK_SECTORS;
@@ -1673,17 +1788,15 @@ static void r5l_recovery_load_parity(struct r5l_log *log,
        struct r5conf *conf = mddev->private;
 
        ctx->meta_total_blocks += BLOCK_SECTORS * conf->max_degraded;
-       sync_page_io(log->rdev, log_offset, PAGE_SIZE,
-                    sh->dev[sh->pd_idx].page, REQ_OP_READ, 0, false);
+       r5l_recovery_read_page(log, ctx, sh->dev[sh->pd_idx].page, log_offset);
        sh->dev[sh->pd_idx].log_checksum =
                le32_to_cpu(payload->checksum[0]);
        set_bit(R5_Wantwrite, &sh->dev[sh->pd_idx].flags);
 
        if (sh->qd_idx >= 0) {
-               sync_page_io(log->rdev,
-                            r5l_ring_add(log, log_offset, BLOCK_SECTORS),
-                            PAGE_SIZE, sh->dev[sh->qd_idx].page,
-                            REQ_OP_READ, 0, false);
+               r5l_recovery_read_page(
+                       log, ctx, sh->dev[sh->qd_idx].page,
+                       r5l_ring_add(log, log_offset, BLOCK_SECTORS));
                sh->dev[sh->qd_idx].log_checksum =
                        le32_to_cpu(payload->checksum[1]);
                set_bit(R5_Wantwrite, &sh->dev[sh->qd_idx].flags);
@@ -1814,14 +1927,15 @@ r5c_recovery_replay_stripes(struct list_head *cached_stripe_list,
 
 /* if matches return 0; otherwise return -EINVAL */
 static int
-r5l_recovery_verify_data_checksum(struct r5l_log *log, struct page *page,
+r5l_recovery_verify_data_checksum(struct r5l_log *log,
+                                 struct r5l_recovery_ctx *ctx,
+                                 struct page *page,
                                  sector_t log_offset, __le32 log_checksum)
 {
        void *addr;
        u32 checksum;
 
-       sync_page_io(log->rdev, log_offset, PAGE_SIZE,
-                    page, REQ_OP_READ, 0, false);
+       r5l_recovery_read_page(log, ctx, page, log_offset);
        addr = kmap_atomic(page);
        checksum = crc32c_le(log->uuid_checksum, addr, PAGE_SIZE);
        kunmap_atomic(addr);
@@ -1853,17 +1967,17 @@ r5l_recovery_verify_data_checksum_for_mb(struct r5l_log *log,
 
                if (payload->header.type == R5LOG_PAYLOAD_DATA) {
                        if (r5l_recovery_verify_data_checksum(
-                                   log, page, log_offset,
+                                   log, ctx, page, log_offset,
                                    payload->checksum[0]) < 0)
                                goto mismatch;
                } else if (payload->header.type == R5LOG_PAYLOAD_PARITY) {
                        if (r5l_recovery_verify_data_checksum(
-                                   log, page, log_offset,
+                                   log, ctx, page, log_offset,
                                    payload->checksum[0]) < 0)
                                goto mismatch;
                        if (conf->max_degraded == 2 && /* q for RAID 6 */
                            r5l_recovery_verify_data_checksum(
-                                   log, page,
+                                   log, ctx, page,
                                    r5l_ring_add(log, log_offset,
                                                 BLOCK_SECTORS),
                                    payload->checksum[1]) < 0)
@@ -2241,55 +2355,70 @@ static void r5c_recovery_flush_data_only_stripes(struct r5l_log *log,
 static int r5l_recovery_log(struct r5l_log *log)
 {
        struct mddev *mddev = log->rdev->mddev;
-       struct r5l_recovery_ctx ctx;
+       struct r5l_recovery_ctx *ctx;
        int ret;
        sector_t pos;
 
-       ctx.pos = log->last_checkpoint;
-       ctx.seq = log->last_cp_seq;
-       ctx.meta_page = alloc_page(GFP_KERNEL);
-       ctx.data_only_stripes = 0;
-       ctx.data_parity_stripes = 0;
-       INIT_LIST_HEAD(&ctx.cached_list);
-
-       if (!ctx.meta_page)
+       ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+       if (!ctx)
                return -ENOMEM;
 
-       ret = r5c_recovery_flush_log(log, &ctx);
-       __free_page(ctx.meta_page);
+       ctx->pos = log->last_checkpoint;
+       ctx->seq = log->last_cp_seq;
+       INIT_LIST_HEAD(&ctx->cached_list);
+       ctx->meta_page = alloc_page(GFP_KERNEL);
 
-       if (ret)
-               return ret;
+       if (!ctx->meta_page) {
+               ret =  -ENOMEM;
+               goto meta_page;
+       }
+
+       if (r5l_recovery_allocate_ra_pool(log, ctx) != 0) {
+               ret = -ENOMEM;
+               goto ra_pool;
+       }
 
-       pos = ctx.pos;
-       ctx.seq += 10000;
+       ret = r5c_recovery_flush_log(log, ctx);
 
+       if (ret)
+               goto error;
 
-       if ((ctx.data_only_stripes == 0) && (ctx.data_parity_stripes == 0))
+       pos = ctx->pos;
+       ctx->seq += 10000;
+
+       if ((ctx->data_only_stripes == 0) && (ctx->data_parity_stripes == 0))
                pr_debug("md/raid:%s: starting from clean shutdown\n",
                         mdname(mddev));
        else
                pr_debug("md/raid:%s: recovering %d data-only stripes and %d data-parity stripes\n",
-                        mdname(mddev), ctx.data_only_stripes,
-                        ctx.data_parity_stripes);
-
-       if (ctx.data_only_stripes == 0) {
-               log->next_checkpoint = ctx.pos;
-               r5l_log_write_empty_meta_block(log, ctx.pos, ctx.seq++);
-               ctx.pos = r5l_ring_add(log, ctx.pos, BLOCK_SECTORS);
-       } else if (r5c_recovery_rewrite_data_only_stripes(log, &ctx)) {
+                        mdname(mddev), ctx->data_only_stripes,
+                        ctx->data_parity_stripes);
+
+       if (ctx->data_only_stripes == 0) {
+               log->next_checkpoint = ctx->pos;
+               r5l_log_write_empty_meta_block(log, ctx->pos, ctx->seq++);
+               ctx->pos = r5l_ring_add(log, ctx->pos, BLOCK_SECTORS);
+       } else if (r5c_recovery_rewrite_data_only_stripes(log, ctx)) {
                pr_err("md/raid:%s: failed to rewrite stripes to journal\n",
                       mdname(mddev));
-               return -EIO;
+               ret =  -EIO;
+               goto error;
        }
 
-       log->log_start = ctx.pos;
-       log->seq = ctx.seq;
+       log->log_start = ctx->pos;
+       log->seq = ctx->seq;
        log->last_checkpoint = pos;
        r5l_write_super(log, pos);
 
-       r5c_recovery_flush_data_only_stripes(log, &ctx);
-       return 0;
+       r5c_recovery_flush_data_only_stripes(log, ctx);
+       ret = 0;
+error:
+       r5l_recovery_free_ra_pool(log, ctx);
+ra_pool:
+       __free_page(ctx->meta_page);
+meta_page:
+       kfree(ctx);
+       return ret;
 }
 
 static void r5l_write_super(struct r5l_log *log, sector_t cp)