btrfs: scrub: merge SCRUB_PAGES_PER_RD_BIO and SCRUB_PAGES_PER_WR_BIO

These two values were introduced in commit aca5df3e0ea8 ("Btrfs: add code
to scrub to copy read data to another disk") as an optimization.

But the truth is, block layer scheduler can do whatever it wants to
merge/split bios to improve performance.

Doing such "optimization" is not really going to affect much, especially
considering how good current block layer optimizations are doing.
Remove such old and immature optimization from our code.

Since we're here, also change BUG_ON()s using these two macros to use
ASSERT()s.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 0870d8db92cd0580aca26e87744f8a08669b60ca..4afa5ae179893cffd183d6f94767b606b503e524 100644 (file)
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -39,14 +39,14 @@ struct scrub_block;
 struct scrub_ctx;
 
 /*
- * the following three values only influence the performance.
+ * The following three values only influence the performance.
+ *
  * The last one configures the number of parallel and outstanding I/O
- * operations. The first two values configure an upper limit for the number
+ * operations. The first one configures an upper limit for the number
  * of (dynamically allocated) pages that are added to a bio.
  */
-#define SCRUB_PAGES_PER_RD_BIO 32      /* 128k per bio */
-#define SCRUB_PAGES_PER_WR_BIO 32      /* 128k per bio */
-#define SCRUB_BIOS_PER_SCTX    64      /* 8MB per device in flight */
+#define SCRUB_PAGES_PER_BIO    32      /* 128KiB per bio for x86 */
+#define SCRUB_BIOS_PER_SCTX    64      /* 8MiB per device in flight for x86 */
 
 /*
  * The following value times PAGE_SIZE needs to be large enough to match the
@@ -87,11 +87,7 @@ struct scrub_bio {
        blk_status_t            status;
        u64                     logical;
        u64                     physical;
-#if SCRUB_PAGES_PER_WR_BIO >= SCRUB_PAGES_PER_RD_BIO
-       struct scrub_page       *pagev[SCRUB_PAGES_PER_WR_BIO];
-#else
-       struct scrub_page       *pagev[SCRUB_PAGES_PER_RD_BIO];
-#endif
+       struct scrub_page       *pagev[SCRUB_PAGES_PER_BIO];
        int                     page_count;
        int                     next_free;
        struct btrfs_work       work;
@@ -162,7 +158,7 @@ struct scrub_ctx {
        struct list_head        csum_list;
        atomic_t                cancel_req;
        int                     readonly;
-       int                     pages_per_rd_bio;
+       int                     pages_per_bio;
 
        /* State of IO submission throttling affecting the associated device */
        ktime_t                 throttle_deadline;
@@ -173,7 +169,6 @@ struct scrub_ctx {
 
        struct scrub_bio        *wr_curr_bio;
        struct mutex            wr_lock;
-       int                     pages_per_wr_bio; /* <= SCRUB_PAGES_PER_WR_BIO */
        struct btrfs_device     *wr_tgtdev;
        bool                    flush_all_writes;
 
@@ -577,7 +572,7 @@ static noinline_for_stack struct scrub_ctx *scrub_setup_ctx(
                goto nomem;
        refcount_set(&sctx->refs, 1);
        sctx->is_dev_replace = is_dev_replace;
-       sctx->pages_per_rd_bio = SCRUB_PAGES_PER_RD_BIO;
+       sctx->pages_per_bio = SCRUB_PAGES_PER_BIO;
        sctx->curr = -1;
        sctx->fs_info = fs_info;
        INIT_LIST_HEAD(&sctx->csum_list);
@@ -615,7 +610,6 @@ static noinline_for_stack struct scrub_ctx *scrub_setup_ctx(
        sctx->wr_curr_bio = NULL;
        if (is_dev_replace) {
                WARN_ON(!fs_info->dev_replace.tgtdev);
-               sctx->pages_per_wr_bio = SCRUB_PAGES_PER_WR_BIO;
                sctx->wr_tgtdev = fs_info->dev_replace.tgtdev;
                sctx->flush_all_writes = false;
        }
@@ -1674,7 +1668,7 @@ again:
                sbio->dev = sctx->wr_tgtdev;
                bio = sbio->bio;
                if (!bio) {
-                       bio = btrfs_bio_alloc(sctx->pages_per_wr_bio);
+                       bio = btrfs_bio_alloc(sctx->pages_per_bio);
                        sbio->bio = bio;
                }
 
@@ -1707,7 +1701,7 @@ again:
        sbio->pagev[sbio->page_count] = spage;
        scrub_page_get(spage);
        sbio->page_count++;
-       if (sbio->page_count == sctx->pages_per_wr_bio)
+       if (sbio->page_count == sctx->pages_per_bio)
                scrub_wr_submit(sctx);
        mutex_unlock(&sctx->wr_lock);
 
@@ -1754,7 +1748,7 @@ static void scrub_wr_bio_end_io_worker(struct btrfs_work *work)
        struct scrub_ctx *sctx = sbio->sctx;
        int i;
 
-       WARN_ON(sbio->page_count > SCRUB_PAGES_PER_WR_BIO);
+       ASSERT(sbio->page_count <= SCRUB_PAGES_PER_BIO);
        if (sbio->status) {
                struct btrfs_dev_replace *dev_replace =
                        &sbio->sctx->fs_info->dev_replace;
@@ -2100,7 +2094,7 @@ again:
                sbio->dev = spage->dev;
                bio = sbio->bio;
                if (!bio) {
-                       bio = btrfs_bio_alloc(sctx->pages_per_rd_bio);
+                       bio = btrfs_bio_alloc(sctx->pages_per_bio);
                        sbio->bio = bio;
                }
 
@@ -2134,7 +2128,7 @@ again:
        scrub_block_get(sblock); /* one for the page added to the bio */
        atomic_inc(&sblock->outstanding_pages);
        sbio->page_count++;
-       if (sbio->page_count == sctx->pages_per_rd_bio)
+       if (sbio->page_count == sctx->pages_per_bio)
                scrub_submit(sctx);
 
        return 0;
@@ -2368,7 +2362,7 @@ static void scrub_bio_end_io_worker(struct btrfs_work *work)
        struct scrub_ctx *sctx = sbio->sctx;
        int i;
 
-       BUG_ON(sbio->page_count > SCRUB_PAGES_PER_RD_BIO);
+       ASSERT(sbio->page_count <= SCRUB_PAGES_PER_BIO);
        if (sbio->status) {
                for (i = 0; i < sbio->page_count; i++) {
                        struct scrub_page *spage = sbio->pagev[i];