[RFC PATCH 17/17] btrfs: add mount option "priority_alloc=%s"

[Su Yue <suy.fnst@cn.fujitsu.com>]

Add mount option "priority_alloc=%s", now %s only supports "usage" and
"off". The latter is used for remount.
"priority_alloc=usage" will active priority aware allocator.
This mount option changes the way of find_free_extent to search
block groups and may cost more time.

Signed-off-by: Su Yue <suy.fnst@cn.fujitsu.com>
---
 fs/btrfs/super.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index cbc9d0d2c12d..4a6ccd4c29fd 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -326,6 +326,7 @@ enum {
 	Opt_treelog, Opt_notreelog,
 	Opt_usebackuproot,
 	Opt_user_subvol_rm_allowed,
+	Opt_priority_allocator,
 
 	/* Deprecated options */
 	Opt_alloc_start,
@@ -393,6 +394,7 @@ static const match_table_t tokens = {
 	{Opt_notreelog, "notreelog"},
 	{Opt_usebackuproot, "usebackuproot"},
 	{Opt_user_subvol_rm_allowed, "user_subvol_rm_allowed"},
+	{Opt_priority_allocator, "priority_alloc=%s"},
 
 	/* Deprecated options */
 	{Opt_alloc_start, "alloc_start=%s"},
@@ -765,6 +767,18 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 		case Opt_skip_balance:
 			btrfs_set_opt(info->mount_opt, SKIP_BALANCE);
 			break;
+		case Opt_priority_allocator:
+			if (strcmp(args[0].from, "usage") == 0) {
+				btrfs_set_and_info(info, PRIORITY_USAGE,
+				   "using priority usage-aware allocator");
+			} else if (strcmp(args[0].from, "off") == 0) {
+				btrfs_clear_and_info(info, PRIORITY_USAGE,
+				   "priority awareallocator disabled");
+			} else {
+				ret = -EINVAL;
+				goto out;
+			}
+			break;
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
 		case Opt_check_integrity_including_extent_data:
 			btrfs_info(info,
@@ -1337,6 +1351,10 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 		seq_puts(seq, ",inode_cache");
 	if (btrfs_test_opt(info, SKIP_BALANCE))
 		seq_puts(seq, ",skip_balance");
+	if (btrfs_test_opt(info, PRIORITY_USAGE))
+		seq_puts(seq, ",priority_alloc=usage");
+	else
+		seq_puts(seq, ",priority_alloc=off");
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
 	if (btrfs_test_opt(info, CHECK_INTEGRITY_INCLUDING_EXTENT_DATA))
 		seq_puts(seq, ",check_int_data");
-- 
2.19.1