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>

1 files changed, 9 insertions, 0 deletions

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: