ext4: convert file system to meta_bg if needed during resizing

If we have run out of reserved gdt blocks, then clear the resize_inode
feature and enable the meta_bg feature, so that we can continue
resizing the file system seamlessly.

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

1 files changed, 133 insertions, 17 deletions

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index a5be589c85b..5932ab5ca53 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1756,6 +1756,99 @@ int ext4_group_extend(struct super_block *sb, struct ext4_super_block *es,
         return err;
 } /* ext4_group_extend */
 
+
+static int num_desc_blocks(struct super_block *sb, ext4_group_t groups)
+{
+        return (groups + EXT4_DESC_PER_BLOCK(sb) - 1) / EXT4_DESC_PER_BLOCK(sb);
+}
+
+/*
+ * Release the resize inode and drop the resize_inode feature if there
+ * are no more reserved gdt blocks, and then convert the file system
+ * to enable meta_bg
+ */
+static int ext4_convert_meta_bg(struct super_block *sb, struct inode *inode)
+{
+        handle_t *handle;
+        struct ext4_sb_info *sbi = EXT4_SB(sb);
+        struct ext4_super_block *es = sbi->s_es;
+        struct ext4_inode_info *ei = 0;
+        ext4_fsblk_t nr;
+        int i, ret, err = 0;
+        int credits = 1;
+
+        ext4_msg(sb, KERN_INFO, "Converting file system to meta_bg");
+        if (EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_RESIZE_INODE)) {
+                if (es->s_reserved_gdt_blocks) {
+                        ext4_error(sb, "Unexpected non-zero "
+                                   "s_reserved_gdt_blocks");
+                        return -EPERM;
+                }
+                if (!inode) {
+                        ext4_error(sb, "Unexpected NULL resize_inode");
+                        return -EPERM;
+                }
+                ei = EXT4_I(inode);
+
+                /* Do a quick sanity check of the resize inode */
+                if (inode->i_blocks != 1 << (inode->i_blkbits - 9))
+                        goto invalid_resize_inode;
+                for (i = 0; i < EXT4_N_BLOCKS; i++) {
+                        if (i == EXT4_DIND_BLOCK) {
+                                if (ei->i_data[i])
+                                        continue;
+                                else
+                                        goto invalid_resize_inode;
+                        }
+                        if (ei->i_data[i])
+                                goto invalid_resize_inode;
+                }
+                credits += 3;   /* block bitmap, bg descriptor, resize inode */
+        }
+
+        handle = ext4_journal_start_sb(sb, credits);
+        if (IS_ERR(handle))
+                return PTR_ERR(handle);
+
+        err = ext4_journal_get_write_access(handle, sbi->s_sbh);
+        if (err)
+                goto errout;
+
+        EXT4_CLEAR_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_RESIZE_INODE);
+        EXT4_SET_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG);
+        sbi->s_es->s_first_meta_bg =
+                cpu_to_le32(num_desc_blocks(sb, sbi->s_groups_count));
+
+        err = ext4_handle_dirty_super(handle, sb);
+        if (err) {
+                ext4_std_error(sb, err);
+                goto errout;
+        }
+
+        if (inode) {
+                nr = le32_to_cpu(ei->i_data[EXT4_DIND_BLOCK]);
+                ext4_free_blocks(handle, inode, NULL, nr, 1,
+                                 EXT4_FREE_BLOCKS_METADATA |
+                                 EXT4_FREE_BLOCKS_FORGET);
+                ei->i_data[EXT4_DIND_BLOCK] = 0;
+                inode->i_blocks = 0;
+
+                err = ext4_mark_inode_dirty(handle, inode);
+                if (err)
+                        ext4_std_error(sb, err);
+        }
+
+errout:
+        ret = ext4_journal_stop(handle);
+        if (!err)
+                err = ret;
+        return ret;
+
+invalid_resize_inode:
+        ext4_error(sb, "corrupted/inconsistent resize inode");
+        return -EINVAL;
+}
+
 /*
  * ext4_resize_fs() resizes a fs to new size specified by @n_blocks_count
  *
@@ -1772,13 +1865,14 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
         ext4_grpblk_t add, offset;
         unsigned long n_desc_blocks;
         unsigned long o_desc_blocks;
-        unsigned long desc_blocks;
         ext4_group_t o_group;
         ext4_group_t n_group;
         ext4_fsblk_t o_blocks_count;
+        ext4_fsblk_t n_blocks_count_retry = 0;
         int err = 0, flexbg_size = 1 << sbi->s_log_groups_per_flex;
         int meta_bg;
 
+retry:
         o_blocks_count = ext4_blocks_count(es);
 
         if (test_opt(sb, DEBUG))
@@ -1798,11 +1892,8 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
         ext4_get_group_no_and_offset(sb, n_blocks_count - 1, &n_group, &offset);
         ext4_get_group_no_and_offset(sb, o_blocks_count - 1, &o_group, &offset);
 
-        n_desc_blocks = (n_group + EXT4_DESC_PER_BLOCK(sb)) /
-                         EXT4_DESC_PER_BLOCK(sb);
-        o_desc_blocks = (sbi->s_groups_count + EXT4_DESC_PER_BLOCK(sb) - 1) /
-                         EXT4_DESC_PER_BLOCK(sb);
-        desc_blocks = n_desc_blocks - o_desc_blocks;
+        n_desc_blocks = num_desc_blocks(sb, n_group + 1);
+        o_desc_blocks = num_desc_blocks(sb, sbi->s_groups_count);
 
         meta_bg = EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG);
 
@@ -1812,20 +1903,37 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
                                    "simultaneously");
                         return -EINVAL;
                 }
-                if (le16_to_cpu(es->s_reserved_gdt_blocks) < desc_blocks) {
-                        ext4_warning(sb,
-                                     "No reserved GDT blocks, can't resize");
-                        return -EPERM;
+                if (n_desc_blocks > o_desc_blocks +
+                    le16_to_cpu(es->s_reserved_gdt_blocks)) {
+                        n_blocks_count_retry = n_blocks_count;
+                        n_desc_blocks = o_desc_blocks +
+                                le16_to_cpu(es->s_reserved_gdt_blocks);
+                        n_group = n_desc_blocks * EXT4_DESC_PER_BLOCK(sb);
+                        n_blocks_count = n_group * EXT4_BLOCKS_PER_GROUP(sb);
+                        n_group--; /* set to last group number */
                 }
-                resize_inode = ext4_iget(sb, EXT4_RESIZE_INO);
+
+                if (!resize_inode)
+                        resize_inode = ext4_iget(sb, EXT4_RESIZE_INO);
                 if (IS_ERR(resize_inode)) {
                         ext4_warning(sb, "Error opening resize inode");
                         return PTR_ERR(resize_inode);
                 }
-        } else if (!meta_bg) {
-                ext4_warning(sb, "File system features do not permit "
-                             "online resize");
-                return -EPERM;
+        }
+
+        if ((!resize_inode && !meta_bg) || n_group == o_group) {
+                err = ext4_convert_meta_bg(sb, resize_inode);
+                if (err)
+                        goto out;
+                if (resize_inode) {
+                        iput(resize_inode);
+                        resize_inode = NULL;
+                }
+                if (n_blocks_count_retry) {
+                        n_blocks_count = n_blocks_count_retry;
+                        n_blocks_count_retry = 0;
+                        goto retry;
+                }
         }
 
         /* See if the device is actually as big as what was requested */
@@ -1876,13 +1984,21 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
                         break;
         }
 
+        if (!err && n_blocks_count_retry) {
+                n_blocks_count = n_blocks_count_retry;
+                n_blocks_count_retry = 0;
+                free_flex_gd(flex_gd);
+                flex_gd = NULL;
+                goto retry;
+        }
+
 out:
         if (flex_gd)
                 free_flex_gd(flex_gd);
         if (resize_inode != NULL)
                 iput(resize_inode);
         if (test_opt(sb, DEBUG))
-                ext4_msg(sb, KERN_DEBUG, "resized filesystem from %llu "
-                       "upto %llu blocks", o_blocks_count, n_blocks_count);
+                ext4_msg(sb, KERN_DEBUG, "resized filesystem to %llu",
+                         n_blocks_count);
         return err;
 }