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Message-ID: <2359eed20909231228m2050cf65pa9029f931f655b10@mail.gmail.com>
Date: Wed, 23 Sep 2009 14:28:03 -0500
From: Will Drewry <redpig@...aspill.org>
To: Andreas Dilger <adilger@....com>
Cc: tytso@....edu, linux-ext4@...r.kernel.org
Subject: Re: [PATCH][RFC] resize2fs and uninit_bg questions
On Wed, Sep 23, 2009 at 4:34 AM, Andreas Dilger <adilger@....com> wrote:
> On Sep 19, 2009 07:19 -0500, Will Drewry wrote:
>> @@ -482,6 +482,8 @@ retry:
>>
>> csum_flag = EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
>> EXT4_FEATURE_RO_COMPAT_GDT_CSUM);
>> + lazy_flag = EXT2_HAS_COMPAT_FEATURE(fs->super,
>> + EXT2_FEATURE_COMPAT_LAZY_BG);
>> adj = old_fs->group_desc_count;
>> max_group = fs->group_desc_count - adj;
>> if (fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG)
>> @@ -496,9 +498,12 @@ retry:
>> adjblocks = 0;
>>
>> fs->group_desc[i].bg_flags = 0;
>> - if (csum_flag)
>> - fs->group_desc[i].bg_flags |= EXT2_BG_INODE_UNINIT |
>> - EXT2_BG_INODE_ZEROED;
>> + if (csum_flag) {
>> + fs->group_desc[i].bg_flags |= EXT2_BG_INODE_UNINIT;
>> + if (!lazy_flag) {
>> + fs->group_desc[i].bg_flags |= EXT2_BG_INODE_ZEROED;
>> + }
>> + }
>
> This code could be cleaned up a bit by assigning "EXT2_BG_INODE_ZEROED" to
> lazy_flag so that you don't need to check this each time:
>
> lazy_flag = EXT2_HAS_COMPAT_FEATURE(fs->super,
> EXT2_FEATURE_COMPAT_LAZY_BG) ?
> EXT2_BG_INODE_ZEROED : 0;
>
> if (csum_flag)
> fs->group_desc[i].bg_flags |=
> EXT2_BG_INODE_UNINIT | lazy_flag;
>
> Still waiting to head from Ted on the use of COMPAT_LAZY_BG.
Ah nice - I can definitely do that. I also think I mangled the spaces
v tabs on the ext4.h part of the patch. If COMPAT_LAZY_BG is off limits,
I can easily use some other flag/indicator.
That aside, I've also got a barebones kernel patch which supports lazy
online resizing which accompanies the e2fsprogs patch above. I realize
it is probably less-than-practical until there is an initializing
thread, but I'd appreciate any feedback if possible -- even if just to
ensure I'm understanding things correctly.
Thanks!
will
Signed-off-by: Will Drewry <redpig@...aspill.org>
---
fs/ext4/ext4.h | 1 +
fs/ext4/resize.c | 38 ++++++++++++++++++++++++++++++++++++--
2 files changed, 37 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 9714db3..24d2880 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1043,6 +1043,7 @@ static inline int ext4_valid_inum(struct
super_block *sb, unsigned long ino)
#define EXT4_FEATURE_COMPAT_EXT_ATTR 0x0008
#define EXT4_FEATURE_COMPAT_RESIZE_INODE 0x0010
#define EXT4_FEATURE_COMPAT_DIR_INDEX 0x0020
+#define EXT4_FEATURE_COMPAT_LAZY_BG 0x0040
#define EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER 0x0001
#define EXT4_FEATURE_RO_COMPAT_LARGE_FILE 0x0002
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 68b0351..faf9263 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -183,7 +183,7 @@ static int setup_new_group_blocks(struct super_block *sb,
handle_t *handle;
ext4_fsblk_t block;
ext4_grpblk_t bit;
- int i;
+ int i, lazy = 0;
int err = 0, err2;
/* This transaction may be extended/restarted along the way */
@@ -261,13 +261,31 @@ static int setup_new_group_blocks(struct super_block *sb,
input->inode_bitmap - start);
ext4_set_bit(input->inode_bitmap - start, bh->b_data);
- /* Zero out all of the inode table blocks */
+ /* Zero out all of the inode table blocks except if the fs supports lazy
+ * itables. */
+ lazy = EXT4_HAS_RO_COMPAT_FEATURE(sb,
+ EXT4_FEATURE_RO_COMPAT_GDT_CSUM) &&
+ EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_LAZY_BG);
+ if (lazy) {
+ ext4_debug("lazy_bg for inode blocks "
+ "%#04llx (+%d) - %#04llx (+%d) ",
+ input->inode_table, input->inode_table - start,
+ input->inode_table + sbi->s_itb_per_group - 1,
+ (input->inode_table - start) + sbi->s_itb_per_group - 1);
+ }
+
for (i = 0, block = input->inode_table, bit = block - start;
i < sbi->s_itb_per_group; i++, bit++, block++) {
struct buffer_head *it;
ext4_debug("clear inode block %#04llx (+%d)\n", block, bit);
+ /* Even though we don't initialize the inode table, we need
+ * to mark the blocks used by it for later init. */
+ if (lazy) {
+ ext4_set_bit(bit, bh->b_data);
+ continue;
+ }
if ((err = extend_or_restart_transaction(handle, 1, bh)))
goto exit_bh;
@@ -286,6 +304,11 @@ static int setup_new_group_blocks(struct super_block *sb,
mark_bitmap_end(input->blocks_count, sb->s_blocksize * 8, bh->b_data);
ext4_handle_dirty_metadata(handle, NULL, bh);
brelse(bh);
+ /* If lazy, we're done since we are marked INODE_UNINIT and that
+ * includes the inode bitmap. (ext4_init_inode_bitmap will do
+ * this for us later). */
+ if (lazy)
+ goto exit_journal;
/* Mark unused entries in inode bitmap used */
ext4_debug("clear inode bitmap %#04llx (+%llu)\n",
input->inode_bitmap, input->inode_bitmap - start);
@@ -868,6 +891,17 @@ int ext4_group_add(struct super_block *sb, struct
ext4_new_group_data *input)
ext4_free_blks_set(sb, gdp, input->free_blocks_count);
ext4_free_inodes_set(sb, gdp, EXT4_INODES_PER_GROUP(sb));
gdp->bg_flags = cpu_to_le16(EXT4_BG_INODE_ZEROED);
+ /* If we can do lazy initialization, we do. */
+ if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM) &&
+ EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_LAZY_BG)) {
+ /* Only use EXT4_BG_INODE_UNINIT and not BLOCK_UNINIT
+ * because we purposefully initialize the block bitmaps
+ * to avoid managing super block backup decisions, making
+ * sure the last block is init'd, etc.
+ */
+ gdp->bg_flags = cpu_to_le16(EXT4_BG_INODE_UNINIT);
+ ext4_itable_unused_set(sb, gdp, EXT4_INODES_PER_GROUP(sb));
+ }
gdp->bg_checksum = ext4_group_desc_csum(sbi, input->group, gdp);
/*
--
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