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Message-Id: <1311816090-5879-1-git-send-email-tytso@mit.edu>
Date: Wed, 27 Jul 2011 21:21:30 -0400
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 -v3] ext4: simplify parameters of add_new_gdb()
From: Yongqiang Yang <xiaoqiangnk@...il.com>
add_new_gdb() only needs the block group number; there is no need to
pass a pointer to struct ext4_new_group_data to add_new_gdb().
Instead of filling in a pointer the struct buffer_head in
add_new_gdb(), it's simpler to have the caller fetch it from the
s_group_desc[] array.
[Fixed error path to handle the case where struct buffer_head *primary
hasn't been set yet. -- Ted]
Signed-off-by: Yongqiang Yang <xiaoqiangnk@...il.com>
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
---
Applied to the ext4 tree, with a bug fix to prevent a null pointer
dereference if add_new_gdb() returns an error.
fs/ext4/resize.c | 39 ++++++++++++++++++++++++---------------
1 files changed, 24 insertions(+), 15 deletions(-)
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 65e5cb6..9e45355 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -394,15 +394,15 @@ static int verify_reserved_gdb(struct super_block *sb,
* fail once we start modifying the data on disk, because JBD has no rollback.
*/
static int add_new_gdb(handle_t *handle, struct inode *inode,
- struct ext4_new_group_data *input,
- struct buffer_head **primary)
+ ext4_group_t group)
{
struct super_block *sb = inode->i_sb;
struct ext4_super_block *es = EXT4_SB(sb)->s_es;
- unsigned long gdb_num = input->group / EXT4_DESC_PER_BLOCK(sb);
+ unsigned long gdb_num = group / EXT4_DESC_PER_BLOCK(sb);
ext4_fsblk_t gdblock = EXT4_SB(sb)->s_sbh->b_blocknr + 1 + gdb_num;
struct buffer_head **o_group_desc, **n_group_desc;
struct buffer_head *dind;
+ struct buffer_head *gdb_bh;
int gdbackups;
struct ext4_iloc iloc;
__le32 *data;
@@ -425,11 +425,12 @@ static int add_new_gdb(handle_t *handle, struct inode *inode,
return -EPERM;
}
- *primary = sb_bread(sb, gdblock);
- if (!*primary)
+ gdb_bh = sb_bread(sb, gdblock);
+ if (!gdb_bh)
return -EIO;
- if ((gdbackups = verify_reserved_gdb(sb, *primary)) < 0) {
+ gdbackups = verify_reserved_gdb(sb, gdb_bh);
+ if (gdbackups < 0) {
err = gdbackups;
goto exit_bh;
}
@@ -444,7 +445,7 @@ static int add_new_gdb(handle_t *handle, struct inode *inode,
data = (__le32 *)dind->b_data;
if (le32_to_cpu(data[gdb_num % EXT4_ADDR_PER_BLOCK(sb)]) != gdblock) {
ext4_warning(sb, "new group %u GDT block %llu not reserved",
- input->group, gdblock);
+ group, gdblock);
err = -EINVAL;
goto exit_dind;
}
@@ -453,7 +454,7 @@ static int add_new_gdb(handle_t *handle, struct inode *inode,
if (unlikely(err))
goto exit_dind;
- err = ext4_journal_get_write_access(handle, *primary);
+ err = ext4_journal_get_write_access(handle, gdb_bh);
if (unlikely(err))
goto exit_sbh;
@@ -492,8 +493,8 @@ static int add_new_gdb(handle_t *handle, struct inode *inode,
}
inode->i_blocks -= (gdbackups + 1) * sb->s_blocksize >> 9;
ext4_mark_iloc_dirty(handle, inode, &iloc);
- memset((*primary)->b_data, 0, sb->s_blocksize);
- err = ext4_handle_dirty_metadata(handle, NULL, *primary);
+ memset(gdb_bh->b_data, 0, sb->s_blocksize);
+ err = ext4_handle_dirty_metadata(handle, NULL, gdb_bh);
if (unlikely(err)) {
ext4_std_error(sb, err);
goto exit_inode;
@@ -503,7 +504,7 @@ static int add_new_gdb(handle_t *handle, struct inode *inode,
o_group_desc = EXT4_SB(sb)->s_group_desc;
memcpy(n_group_desc, o_group_desc,
EXT4_SB(sb)->s_gdb_count * sizeof(struct buffer_head *));
- n_group_desc[gdb_num] = *primary;
+ n_group_desc[gdb_num] = gdb_bh;
EXT4_SB(sb)->s_group_desc = n_group_desc;
EXT4_SB(sb)->s_gdb_count++;
kfree(o_group_desc);
@@ -525,7 +526,7 @@ exit_sbh:
exit_dind:
brelse(dind);
exit_bh:
- brelse(*primary);
+ brelse(gdb_bh);
ext4_debug("leaving with error %d\n", err);
return err;
@@ -833,8 +834,16 @@ int ext4_group_add(struct super_block *sb, struct ext4_new_group_data *input)
if (reserved_gdb && ext4_bg_num_gdb(sb, input->group) &&
(err = reserve_backup_gdb(handle, inode, input)))
goto exit_journal;
- } else if ((err = add_new_gdb(handle, inode, input, &primary)))
- goto exit_journal;
+ } else {
+ /*
+ * Note that we can access new group descriptor block safely
+ * only if add_new_gdb() succeeds.
+ */
+ err = add_new_gdb(handle, inode, input->group);
+ if (err)
+ goto exit_journal;
+ primary = sbi->s_group_desc[gdb_num];
+ }
/*
* OK, now we've set up the new group. Time to make it active.
@@ -944,7 +953,7 @@ int ext4_group_add(struct super_block *sb, struct ext4_new_group_data *input)
exit_journal:
if ((err2 = ext4_journal_stop(handle)) && !err)
err = err2;
- if (!err) {
+ if (!err && primary) {
update_backups(sb, sbi->s_sbh->b_blocknr, (char *)es,
sizeof(struct ext4_super_block));
update_backups(sb, primary->b_blocknr, primary->b_data,
--
1.7.4.1.22.gec8e1.dirty
--
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