Btrfs: autodetect SSD devices

During mount, btrfs will check the queue nonrot flag
for all the devices found in the FS.  If they are all
non-rotating, SSD mode is enabled by default.

If the FS was mounted with -o nossd, the non-rotating
flag is ignored.

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

5 files changed, 24 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index b9d8788b299e..5fa7d7d287a4 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1101,6 +1101,7 @@ struct btrfs_root {
 #define BTRFS_MOUNT_NOTREELOG           (1 << 6)
 #define BTRFS_MOUNT_FLUSHONCOMMIT       (1 << 7)
 #define BTRFS_MOUNT_SSD_SPREAD          (1 << 8)
+#define BTRFS_MOUNT_NOSSD               (1 << 9)
 
 #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/disk-io.c b/fs/btrfs/disk-io.c
index e572cf478a5d..f4dfbb7ab496 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1850,6 +1850,14 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         if (IS_ERR(fs_info->transaction_kthread))
                 goto fail_cleaner;
 
+        if (!btrfs_test_opt(tree_root, SSD) &&
+            !btrfs_test_opt(tree_root, NOSSD) &&
+            !fs_info->fs_devices->rotating) {
+                printk(KERN_INFO "Btrfs detected SSD devices, enabling SSD "
+                       "mode\n");
+                btrfs_set_opt(fs_info->mount_opt, SSD);
+        }
+
         if (btrfs_super_log_root(disk_super) != 0) {
                 u64 bytenr = btrfs_super_log_root(disk_super);
 
@@ -1893,6 +1901,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         fs_info->fs_root = btrfs_read_fs_root_no_name(fs_info, &location);
         if (!fs_info->fs_root)
                 goto fail_trans_kthread;
+
         return tree_root;
 
 fail_trans_kthread:
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 7f5b2889949a..3427db28f6fe 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -184,6 +184,7 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
                 case Opt_nossd:
                         printk(KERN_INFO "btrfs: not using ssd allocation "
                                "scheme\n");
+                        btrfs_set_opt(info->mount_opt, NOSSD);
                         btrfs_clear_opt(info->mount_opt, SSD);
                         btrfs_clear_opt(info->mount_opt, SSD_SPREAD);
                         break;
@@ -438,6 +439,8 @@ 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, NOSSD))
+                seq_puts(seq, ",nossd");
         if (btrfs_test_opt(root, SSD_SPREAD))
                 seq_puts(seq, ",ssd_spread");
         else if (btrfs_test_opt(root, SSD))
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 27d5f37b845f..3f4a5932eac9 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -605,6 +605,9 @@ static int __btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
                 device->in_fs_metadata = 0;
                 device->mode = flags;
 
+                if (!blk_queue_nonrot(bdev_get_queue(bdev)))
+                        fs_devices->rotating = 1;
+
                 fs_devices->open_devices++;
                 if (device->writeable) {
                         fs_devices->rw_devices++;
@@ -1473,6 +1476,9 @@ int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
         root->fs_info->fs_devices->rw_devices++;
         root->fs_info->fs_devices->total_rw_bytes += device->total_bytes;
 
+        if (!blk_queue_nonrot(bdev_get_queue(bdev)))
+                root->fs_info->fs_devices->rotating = 1;
+
         total_bytes = btrfs_super_total_bytes(&root->fs_info->super_copy);
         btrfs_set_super_total_bytes(&root->fs_info->super_copy,
                                     total_bytes + device->total_bytes);
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 5c3ff6d02fd7..3c1f7310421e 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -107,6 +107,11 @@ struct btrfs_fs_devices {
         int seeding;
 
         int opened;
+
+        /* set when we find or add a device that doesn't have the
+         * nonrot flag set
+         */
+        int rotating;
 };
 
 struct btrfs_bio_stripe {