ext4: support simple conversion of extent-mapped inodes to use i_blocks

In order to make it simpler to test the code which support
i_blocks/indirect-mapped inodes, support the conversion of inodes
which are less than 12 blocks and which are contained in no more than
a single extent.

The primary intended use of this code is to converting freshly created
zero-length files and empty directories.

Note that the version of chattr in e2fsprogs 1.42.7 and earlier has a
check that prevents the clearing of the extent flag.  A simple patch
which allows "chattr -e <file>" to work will be checked into the
e2fsprogs git repository.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 59 insertions, 0 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index cbbe8a4deac6..235246719074 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4610,3 +4610,62 @@ int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 
         return error;
 }
+
+/*
+ * Migrate a simple extent-based inode to use the i_blocks[] array
+ */
+int ext4_ind_migrate(struct inode *inode)
+{
+        struct ext4_extent_header       *eh;
+        struct ext4_super_block         *es = EXT4_SB(inode->i_sb)->s_es;
+        struct ext4_inode_info          *ei = EXT4_I(inode);
+        struct ext4_extent              *ex;
+        unsigned int                    i, len;
+        ext4_fsblk_t                    blk;
+        handle_t                        *handle;
+        int                             ret;
+
+        if (!EXT4_HAS_INCOMPAT_FEATURE(inode->i_sb,
+                                       EXT4_FEATURE_INCOMPAT_EXTENTS) ||
+            (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
+                return -EINVAL;
+
+        down_write(&EXT4_I(inode)->i_data_sem);
+        ret = ext4_ext_check_inode(inode);
+        if (ret)
+                goto errout;
+
+        eh = ext_inode_hdr(inode);
+        ex  = EXT_FIRST_EXTENT(eh);
+        if (ext4_blocks_count(es) > EXT4_MAX_BLOCK_FILE_PHYS ||
+            eh->eh_depth != 0 || eh->eh_entries > 1) {
+                ret = -EOPNOTSUPP;
+                goto errout;
+        }
+        if (eh->eh_entries == 0)
+                blk = len = 0;
+        else {
+                len = le16_to_cpu(ex->ee_len);
+                blk = ext4_ext_pblock(ex);
+                if (len > EXT4_NDIR_BLOCKS) {
+                        ret = -EOPNOTSUPP;
+                        goto errout;
+                }
+        }
+
+        handle = ext4_journal_start(inode, EXT4_HT_MIGRATE, 1);
+        if (IS_ERR(handle)) {
+                ret = PTR_ERR(handle);
+                goto errout;
+        }
+
+        ext4_clear_inode_flag(inode, EXT4_INODE_EXTENTS);
+        memset(ei->i_data, 0, sizeof(ei->i_data));
+        for (i=0; i < len; i++)
+                ei->i_data[i] = cpu_to_le32(blk++);
+        ext4_mark_inode_dirty(handle, inode);
+        ext4_journal_stop(handle);
+errout:
+        up_write(&EXT4_I(inode)->i_data_sem);
+        return ret;
+}