Btrfs: Add mount option to enforce a max extent size

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

4 files changed, 65 insertions, 11 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index b51b021fff85..32b24460ec82 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -322,6 +322,7 @@ struct btrfs_fs_info {
         u64 generation;
         u64 last_trans_committed;
         unsigned long mount_opt;
+        u64 max_extent;
         struct btrfs_transaction *running_transaction;
         struct btrfs_super_block super_copy;
         struct extent_buffer *sb_buffer;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 278564178993..7213012c27d5 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -569,6 +569,7 @@ struct btrfs_root *open_ctree(struct super_block *sb)
         fs_info->extent_root = extent_root;
         fs_info->sb = sb;
         fs_info->mount_opt = 0;
+        fs_info->max_extent = (u64)-1;
         fs_info->btree_inode = new_inode(sb);
         fs_info->btree_inode->i_ino = 1;
         fs_info->btree_inode->i_nlink = 1;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 91f3fc43e2a9..686dd03f34f2 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -78,6 +78,7 @@ static int cow_file_range(struct inode *inode, u64 start, u64 end)
         struct btrfs_trans_handle *trans;
         u64 alloc_hint = 0;
         u64 num_bytes;
+        u64 cur_alloc_size;
         u64 blocksize = root->sectorsize;
         struct btrfs_key ins;
         int ret;
@@ -94,17 +95,24 @@ static int cow_file_range(struct inode *inode, u64 start, u64 end)
         if (alloc_hint == EXTENT_MAP_INLINE)
                 goto out;
 
-        ret = btrfs_alloc_extent(trans, root, num_bytes,
-                                 root->root_key.objectid, trans->transid,
-                                 inode->i_ino, start, 0,
-                                 alloc_hint, (u64)-1, &ins, 1);
-        if (ret) {
-                WARN_ON(1);
-                goto out;
+        while(num_bytes > 0) {
+                cur_alloc_size = min(num_bytes, root->fs_info->max_extent);
+                ret = btrfs_alloc_extent(trans, root, cur_alloc_size,
+                                         root->root_key.objectid,
+                                         trans->transid,
+                                         inode->i_ino, start, 0,
+                                         alloc_hint, (u64)-1, &ins, 1);
+                if (ret) {
+                        WARN_ON(1);
+                        goto out;
+                }
+                ret = btrfs_insert_file_extent(trans, root, inode->i_ino,
+                                               start, ins.objectid, ins.offset,
+                                               ins.offset);
+                num_bytes -= cur_alloc_size;
+                alloc_hint = ins.objectid + ins.offset;
+                start += cur_alloc_size;
         }
-        ret = btrfs_insert_file_extent(trans, root, inode->i_ino,
-                                       start, ins.objectid, ins.offset,
-                                       ins.offset);
 out:
         btrfs_end_transaction(trans, root);
         return ret;
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 2116728d1f98..b7323914bf5a 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -34,6 +34,7 @@
 #include <linux/statfs.h>
 #include <linux/compat.h>
 #include <linux/parser.h>
+#include <linux/ctype.h>
 #include "ctree.h"
 #include "disk-io.h"
 #include "transaction.h"
@@ -61,16 +62,42 @@ static void btrfs_put_super (struct super_block * sb)
 }
 
 enum {
-        Opt_subvol, Opt_nodatasum, Opt_nodatacow, Opt_err,
+        Opt_subvol, Opt_nodatasum, Opt_nodatacow, Opt_max_extent, Opt_err,
 };
 
 static match_table_t tokens = {
         {Opt_subvol, "subvol=%s"},
         {Opt_nodatasum, "nodatasum"},
         {Opt_nodatacow, "nodatacow"},
+        {Opt_max_extent, "max_extent=%s"},
         {Opt_err, NULL}
 };
 
+static unsigned long parse_size(char *str)
+{
+        unsigned long res;
+        int mult = 1;
+        char *end;
+        char last;
+
+        res = simple_strtoul(str, &end, 10);
+
+        last = end[0];
+        if (isalpha(last)) {
+                last = tolower(last);
+                switch (last) {
+                case 'g':
+                        mult *= 1024;
+                case 'm':
+                        mult *= 1024;
+                case 'k':
+                        mult *= 1024;
+                }
+                res = res * mult;
+        }
+        return res;
+}
+
 static int parse_options (char * options,
                           struct btrfs_root *root,
                           char **subvol_name)
@@ -118,6 +145,21 @@ static int parse_options (char * options,
                                 btrfs_set_opt(info->mount_opt, NODATASUM);
                         }
                         break;
+                case Opt_max_extent:
+                        if (info) {
+                                char *num = match_strdup(&args[0]);
+                                if (num) {
+                                        info->max_extent = parse_size(num);
+                                        kfree(num);
+
+                                        info->max_extent = max_t(u64,
+                                                         info->max_extent,
+                                                         root->sectorsize);
+                                        printk("btrfs: max_extent at %Lu\n",
+                                               info->max_extent);
+                                }
+                        }
+                        break;
                 default:
                         break;
                 }
@@ -329,6 +371,8 @@ static int btrfs_get_sb(struct file_system_type *fs_type,
         ret = btrfs_get_sb_bdev(fs_type, flags, dev_name, data,
                         btrfs_fill_super, mnt,
                         subvol_name ? subvol_name : "default");
+        if (subvol_name)
+                kfree(subvol_name);
         return ret;
 }