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>

3 files changed, 69 insertions, 13 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index d05ba3886f33..73f3e60f7078 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -403,7 +403,7 @@ struct flex_groups {
 #define EXT4_RESERVED_FL                0x80000000 /* reserved for ext4 lib */
 
 #define EXT4_FL_USER_VISIBLE            0x004BDFFF /* User visible flags */
-#define EXT4_FL_USER_MODIFIABLE         0x004B80FF /* User modifiable flags */
+#define EXT4_FL_USER_MODIFIABLE         0x004380FF /* User modifiable flags */
 
 /* Flags that should be inherited by new inodes from their parent. */
 #define EXT4_FL_INHERITED (EXT4_SECRM_FL | EXT4_UNRM_FL | EXT4_COMPR_FL |\
@@ -2608,6 +2608,7 @@ extern int ext4_find_delalloc_range(struct inode *inode,
 extern int ext4_find_delalloc_cluster(struct inode *inode, ext4_lblk_t lblk);
 extern int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
                         __u64 start, __u64 len);
+extern int ext4_ind_migrate(struct inode *inode);
 
 
 /* move_extent.c */
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;
+}
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 721f4d33e148..a07b7bc0856a 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -83,17 +83,8 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
                         if (!capable(CAP_SYS_RESOURCE))
                                 goto flags_out;
                 }
-                if (oldflags & EXT4_EXTENTS_FL) {
-                        /* We don't support clearning extent flags */
-                        if (!(flags & EXT4_EXTENTS_FL)) {
-                                err = -EOPNOTSUPP;
-                                goto flags_out;
-                        }
-                } else if (flags & EXT4_EXTENTS_FL) {
-                        /* migrate the file */
+                if ((flags ^ oldflags) & EXT4_EXTENTS_FL)
                         migrate = 1;
-                        flags &= ~EXT4_EXTENTS_FL;
-                }
 
                 if (flags & EXT4_EOFBLOCKS_FL) {
                         /* we don't support adding EOFBLOCKS flag */
@@ -137,8 +128,13 @@ flags_err:
                         err = ext4_change_inode_journal_flag(inode, jflag);
                 if (err)
                         goto flags_out;
-                if (migrate)
-                        err = ext4_ext_migrate(inode);
+                if (migrate) {
+                        if (flags & EXT4_EXTENTS_FL)
+                                err = ext4_ext_migrate(inode);
+                        else
+                                err = ext4_ind_migrate(inode);
+                }
+
 flags_out:
                 mutex_unlock(&inode->i_mutex);
                 mnt_drop_write_file(filp);