Btrfs: add mount -o ssd_spread to spread allocations out

Some SSDs perform best when reusing block numbers often, while
others perform much better when clustering strictly allocates
big chunks of unused space.

The default mount -o ssd will find rough groupings of blocks
where there are a bunch of free blocks that might have some
allocated blocks mixed in.

mount -o ssd_spread will make sure there are no allocated blocks
mixed in.  It should perform better on lower end SSDs.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index ce3ab4e1306424ae1ad94d3e4236708becdcfe4b..b9d8788b299ec1f8b1d37801d1f44e311d571190 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1100,6 +1100,7 @@ struct btrfs_root {
 #define BTRFS_MOUNT_COMPRESS           (1 << 5)
 #define BTRFS_MOUNT_NOTREELOG           (1 << 6)
 #define BTRFS_MOUNT_FLUSHONCOMMIT       (1 << 7)
+#define BTRFS_MOUNT_SSD_SPREAD         (1 << 8)
 
 #define btrfs_clear_opt(o, opt)                ((o) &= ~BTRFS_MOUNT_##opt)
 #define btrfs_set_opt(o, opt)          ((o) |= BTRFS_MOUNT_##opt)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index a42419c276e21686dfd9949497541d4936b17b44..3355d7ea830818bee66dfdf929246fec32841a0c 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3607,7 +3607,7 @@ refill_cluster:
                        last_ptr_loop = 0;
 
                        /* allocate a cluster in this block group */
-                       ret = btrfs_find_space_cluster(trans,
+                       ret = btrfs_find_space_cluster(trans, root,
                                               block_group, last_ptr,
                                               offset, num_bytes,
                                               empty_cluster + empty_size);

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index ac23476beb6eac1e6c279cd269001bb67742f9a9..4538e48581a5171b33af2d3d2c632dbff4e412e2 100644 (file)
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -579,6 +579,7 @@ out:
  * it returns -enospc
  */
 int btrfs_find_space_cluster(struct btrfs_trans_handle *trans,
+                            struct btrfs_root *root,
                             struct btrfs_block_group_cache *block_group,
                             struct btrfs_free_cluster *cluster,
                             u64 offset, u64 bytes, u64 empty_size)
@@ -595,7 +596,9 @@ int btrfs_find_space_cluster(struct btrfs_trans_handle *trans,
        int ret;
 
        /* for metadata, allow allocates with more holes */
-       if (block_group->flags & BTRFS_BLOCK_GROUP_METADATA) {
+       if (btrfs_test_opt(root, SSD_SPREAD)) {
+               min_bytes = bytes + empty_size;
+       } else if (block_group->flags & BTRFS_BLOCK_GROUP_METADATA) {
                /*
                 * we want to do larger allocations when we are
                 * flushing out the delayed refs, it helps prevent

diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h
index ab0bdc0a63ce2da4390616b236a3e868b2e6ce18..266fb876405442841b31b7e8219fff82e339d821 100644 (file)
--- a/fs/btrfs/free-space-cache.h
+++ b/fs/btrfs/free-space-cache.h
@@ -31,6 +31,7 @@ void btrfs_dump_free_space(struct btrfs_block_group_cache *block_group,
                           u64 bytes);
 u64 btrfs_block_group_free_space(struct btrfs_block_group_cache *block_group);
 int btrfs_find_space_cluster(struct btrfs_trans_handle *trans,
+                            struct btrfs_root *root,
                             struct btrfs_block_group_cache *block_group,
                             struct btrfs_free_cluster *cluster,
                             u64 offset, u64 bytes, u64 empty_size);

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 22855a18eb487834d489a70f07357b9c91281d22..7f5b2889949a19f510b55b870721433834895db0 100644 (file)
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -66,8 +66,8 @@ static void btrfs_put_super(struct super_block *sb)
 enum {
        Opt_degraded, Opt_subvol, Opt_device, Opt_nodatasum, Opt_nodatacow,
        Opt_max_extent, Opt_max_inline, Opt_alloc_start, Opt_nobarrier,
-       Opt_ssd, Opt_nossd, Opt_thread_pool, Opt_noacl,  Opt_compress,
-       Opt_notreelog, Opt_ratio, Opt_flushoncommit, Opt_err,
+       Opt_ssd, Opt_nossd, Opt_ssd_spread, Opt_thread_pool, Opt_noacl,
+       Opt_compress, Opt_notreelog, Opt_ratio, Opt_flushoncommit, Opt_err,
 };
 
 static match_table_t tokens = {
@@ -83,6 +83,7 @@ static match_table_t tokens = {
        {Opt_thread_pool, "thread_pool=%d"},
        {Opt_compress, "compress"},
        {Opt_ssd, "ssd"},
+       {Opt_ssd_spread, "ssd_spread"},
        {Opt_nossd, "nossd"},
        {Opt_noacl, "noacl"},
        {Opt_notreelog, "notreelog"},
@@ -174,9 +175,17 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
                        printk(KERN_INFO "btrfs: use ssd allocation scheme\n");
                        btrfs_set_opt(info->mount_opt, SSD);
                        break;
+               case Opt_ssd_spread:
+                       printk(KERN_INFO "btrfs: use spread ssd "
+                              "allocation scheme\n");
+                       btrfs_set_opt(info->mount_opt, SSD);
+                       btrfs_set_opt(info->mount_opt, SSD_SPREAD);
+                       break;
                case Opt_nossd:
-                       printk(KERN_INFO "btrfs: not using ssd allocation scheme\n");
+                       printk(KERN_INFO "btrfs: not using ssd allocation "
+                              "scheme\n");
                        btrfs_clear_opt(info->mount_opt, SSD);
+                       btrfs_clear_opt(info->mount_opt, SSD_SPREAD);
                        break;
                case Opt_nobarrier:
                        printk(KERN_INFO "btrfs: turning off barriers\n");
@@ -429,7 +438,9 @@ static int btrfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
                seq_printf(seq, ",thread_pool=%d", info->thread_pool_size);
        if (btrfs_test_opt(root, COMPRESS))
                seq_puts(seq, ",compress");
-       if (btrfs_test_opt(root, SSD))
+       if (btrfs_test_opt(root, SSD_SPREAD))
+               seq_puts(seq, ",ssd_spread");
+       else if (btrfs_test_opt(root, SSD))
                seq_puts(seq, ",ssd");
        if (btrfs_test_opt(root, NOTREELOG))
                seq_puts(seq, ",notreelog");