| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Tue, 30 Aug 2011 16:10:14 +0800
From: Yongqiang Yang <xiaoqiangnk@...il.com>
To: tytso@....edu
Cc: adilger@...ger.ca, linux-ext4@...r.kernel.org,
Yongqiang Yang <xiaoqiangnk@...il.com>
Subject: [PATCH v2 04/15] ext4: add a function which updates super block
This patch adds a function named ext4_update_super() which updates
super block and whose code is copied from ext4_group_add().
The function will be used by new resize implementation.
Signed-off-by: Yongqiang Yang <xiaoqiangnk@...il.com>
---
fs/ext4/resize.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 72 insertions(+), 0 deletions(-)
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 66ca671..d20b29c 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -831,6 +831,78 @@ static int ext4_setup_new_desc(handle_t *handle, struct super_block *sb,
return err;
}
+/*
+ * ext4_update_super() updates super so that new the added group can be seen
+ * by the filesystem.
+ *
+ * @sb: super block
+ */
+static void ext4_update_super(struct super_block *sb,
+ struct ext4_new_group_data *input)
+{
+ struct ext4_sb_info *sbi = EXT4_SB(sb);
+ struct ext4_super_block *es = sbi->s_es;
+
+ /*
+ * 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.
+ */
+ ext4_blocks_count_set(es, ext4_blocks_count(es) +
+ input->blocks_count);
+ le32_add_cpu(&es->s_inodes_count, EXT4_INODES_PER_GROUP(sb));
+
+ /*
+ * 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++;
+
+ /* Update the reserved block counts only once the new group is
+ * active. */
+ ext4_r_blocks_count_set(es, ext4_r_blocks_count(es) +
+ input->reserved_blocks);
+
+ /* Update the free space counts */
+ percpu_counter_add(&sbi->s_freeblocks_counter,
+ input->free_blocks_count);
+ percpu_counter_add(&sbi->s_freeinodes_counter,
+ EXT4_INODES_PER_GROUP(sb));
+
+ 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, input->group);
+ atomic_add(input->free_blocks_count,
+ &sbi->s_flex_groups[flex_group].free_blocks);
+ atomic_add(EXT4_INODES_PER_GROUP(sb),
+ &sbi->s_flex_groups[flex_group].free_inodes);
+ }
+
+}
+
/* 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
--
1.7.5.1
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Powered by blists - more mailing lists