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Message-Id: <1325653654-10478-7-git-send-email-tytso@mit.edu>
Date: Wed, 4 Jan 2012 00:07:28 -0500
From: Theodore Ts'o <tytso@....edu>
To: Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc: Yongqiang Yang <xiaoqiangnk@...il.com>,
"Theodore Ts'o" <tytso@....edu>
Subject: [PATCH V7 06/12] ext4: add a function which updates the super block during online resizing
From: Yongqiang Yang <xiaoqiangnk@...il.com>
This patch adds a function named ext4_update_super() which updates
super block so the newly created block groups are visible to the file
system. This code is copied from ext4_group_add().
The function will be used by new resize implementation.
Signed-off-by: Yongqiang Yang <xiaoqiangnk@...il.com>
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
---
fs/ext4/resize.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 94 insertions(+), 0 deletions(-)
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 098bdb8..eb0aebc 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1142,6 +1142,100 @@ static int ext4_setup_new_descs(handle_t *handle, struct super_block *sb,
return err;
}
+/*
+ * ext4_update_super() updates the super block so that the newly added
+ * groups can be seen by the filesystem.
+ *
+ * @sb: super block
+ * @flex_gd: new added groups
+ */
+static void ext4_update_super(struct super_block *sb,
+ struct ext4_new_flex_group_data *flex_gd)
+{
+ ext4_fsblk_t blocks_count = 0;
+ ext4_fsblk_t free_blocks = 0;
+ ext4_fsblk_t reserved_blocks = 0;
+ struct ext4_new_group_data *group_data = flex_gd->groups;
+ struct ext4_sb_info *sbi = EXT4_SB(sb);
+ struct ext4_super_block *es = sbi->s_es;
+ int i;
+
+ BUG_ON(flex_gd->count == 0 || group_data == NULL);
+ /*
+ * Make the new blocks and inodes valid next. We do this before
+ * increasing the group count so that once the group is enabled,
+ * all of its blocks and inodes are already valid.
+ *
+ * We always allocate group-by-group, then block-by-block or
+ * inode-by-inode within a group, so enabling these
+ * blocks/inodes before the group is live won't actually let us
+ * allocate the new space yet.
+ */
+ for (i = 0; i < flex_gd->count; i++) {
+ blocks_count += group_data[i].blocks_count;
+ free_blocks += group_data[i].free_blocks_count;
+ }
+
+ reserved_blocks = ext4_r_blocks_count(es) * 100;
+ do_div(reserved_blocks, ext4_blocks_count(es));
+ reserved_blocks *= blocks_count;
+ do_div(reserved_blocks, 100);
+
+ ext4_blocks_count_set(es, ext4_blocks_count(es) + blocks_count);
+ le32_add_cpu(&es->s_inodes_count, EXT4_INODES_PER_GROUP(sb) *
+ flex_gd->count);
+
+ /*
+ * We need to protect s_groups_count against other CPUs seeing
+ * inconsistent state in the superblock.
+ *
+ * The precise rules we use are:
+ *
+ * * Writers must perform a smp_wmb() after updating all
+ * dependent data and before modifying the groups count
+ *
+ * * Readers must perform an smp_rmb() after reading the groups
+ * count and before reading any dependent data.
+ *
+ * NB. These rules can be relaxed when checking the group count
+ * while freeing data, as we can only allocate from a block
+ * group after serialising against the group count, and we can
+ * only then free after serialising in turn against that
+ * allocation.
+ */
+ smp_wmb();
+
+ /* Update the global fs size fields */
+ sbi->s_groups_count += flex_gd->count;
+
+ /* Update the reserved block counts only once the new group is
+ * active. */
+ ext4_r_blocks_count_set(es, ext4_r_blocks_count(es) +
+ reserved_blocks);
+
+ /* Update the free space counts */
+ percpu_counter_add(&sbi->s_freeclusters_counter,
+ EXT4_B2C(sbi, free_blocks));
+ percpu_counter_add(&sbi->s_freeinodes_counter,
+ EXT4_INODES_PER_GROUP(sb) * flex_gd->count);
+
+ if (EXT4_HAS_INCOMPAT_FEATURE(sb,
+ EXT4_FEATURE_INCOMPAT_FLEX_BG) &&
+ sbi->s_log_groups_per_flex) {
+ ext4_group_t flex_group;
+ flex_group = ext4_flex_group(sbi, group_data[0].group);
+ atomic_add(EXT4_B2C(sbi, free_blocks),
+ &sbi->s_flex_groups[flex_group].free_clusters);
+ atomic_add(EXT4_INODES_PER_GROUP(sb) * flex_gd->count,
+ &sbi->s_flex_groups[flex_group].free_inodes);
+ }
+
+ if (test_opt(sb, DEBUG))
+ printk(KERN_DEBUG "EXT4-fs: added group %u:"
+ "%llu blocks(%llu free %llu reserved)\n", flex_gd->count,
+ blocks_count, free_blocks, reserved_blocks);
+}
+
/* Add group descriptor data to an existing or new group descriptor block.
* Ensure we handle all possible error conditions _before_ we start modifying
* the filesystem, because we cannot abort the transaction and not have it
--
1.7.8.11.gefc1f.dirty
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