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Date: Mon, 26 Jan 2009 17:39:47 +0530
From: Sandeep K Sinha <sandeepksinha@...il.com>
To: Akira Fujita <a-fujita@...jp.nec.com>
Cc: Greg Freemyer <greg.freemyer@...il.com>,
Derkjan de Haan <haanjdj@...il.com>,
Takashi Sato <t-sato@...jp.nec.com>, linux-ext4@...r.kernel.org
Subject: Re: can't get e4defrag to work
On Mon, Jan 26, 2009 at 1:07 PM, Akira Fujita <a-fujita@...jp.nec.com> wrote:
> Hi Greg,
>
> Greg Freemyer wrote:
>>
>> Will the new defrag patchset be based on the ioctl's that Ted
>> suggested last month?
>
> Yes, but the new defrag that I will release corresponds to (3) of
> Ted's suggestion.
> (http://marc.info/?l=linux-ext4&m=122880166227883&w=3)
>
> For (1) and (2), probably it will be necessary to change
> the allocation method and add new ioctls, so I will address them later.
>
> Have you already worked on these features?
>
Well,
for option (2), I did try it on ext2/3 and it works fine for me.
Same on ext4 was a bit problematic as a lot of interfaces are changing
to the mballoc from balloc.
And I have read lot of changes pipelined for block allocation in ext4.
So, just waiting to get some information on that so that I can do the
same for ext4 as well.
This is a sample code that I tried and it works fine. It you wish, I
can produce a formal version for the same.
Here are the changes:
#diff a/fs/ext2/ioctl.c b/fs/ext2/ioctl.c
19a20,35
> #define EXT2_BG_ALLOC 7
>
> struct ext2fs_bg_range {
> unsigned int bg_start;
> unsigned int bg_end;
> };
>
> struct ext2fs_bg_ioc {
>
> struct ext2fs_bg_range bg_range[10];
> unsigned long fs_bg_range_count;
> unsigned long blk_req_count;
> };
>
> extern ext2_fsblk_t fs_bg_ext2_new_blocks(struct inode *inode, struct ext2fs_bg_range bg[],
> unsigned long fs_bg_range_count, unsigned long *count, int *errp);
25a42
> struct ext2fs_bg_ioc bg_ioc;
27,28c44,45
< int ret;
> int ret ,err;
<
> case EXT2_BG_ALLOC:
> copy_from_user((struct ext2fs_bg_ioc *)&bg_ioc, (const void __user *)arg, sizeof(struct ext2fs_bg_ioc));
> ret = fs_bg_ext2_new_blocks(inode, bg_ioc.bg_range, bg_ioc.fs_bg_range_count,
> &bg_ioc.blk_req_count, &err);
>
> break;
162a198,200
> case EXT2_IOC32_BG_ALLOC_BLOCKS:
> cmd = EXT2_IOC_BG_ALLOC_BLOCKS;
> break;
diff a/fs/ext2/balloc.c b/fs/ext2/balloc.c
16a17
> #include <linux/module.h>
1543a1545,1732
> struct ext2fs_bg_range {
> unsigned int bg_start;
> unsigned int bg_end;
> };
>
> ext2_fsblk_t fs_bg_ext2_new_blocks(struct inode *inode, struct ext2fs_bg_range bg_range[],
> unsigned int fs_bg_range_count, unsigned long *count, int *errp)
> {
> struct buffer_head *bitmap_bh = NULL;
> struct buffer_head *gdp_bh;
> int group_no = 0;
> int goal_group = 0;
> int fs_bg;
> int bg_start = 0, bg_end = 0;
> ext2_grpblk_t grp_alloc_blk; /* blockgroup-relative allocated block*/
> ext2_fsblk_t ret_block; /* filesyetem-wide allocated block */
> ext2_fsblk_t goal; /* goal block for allocation */
> int bgi; /* blockgroup iteration index */
> int performed_allocation = 0;
> ext2_grpblk_t free_blocks; /* number of free blocks in a group */
> struct super_block *sb;
> struct ext2_group_desc *gdp;
> struct ext2_super_block *es;
> struct ext2_sb_info *sbi;
> struct ext2_reserve_window_node *my_rsv = NULL;
> unsigned short windowsz = 0;
> unsigned long ngroups;
> unsigned long num = *count;
>
> sb = inode->i_sb;
> *errp = -ENOSPC;
> if (!sb) {
> printk("ext2_new_blocks: nonexistent device");
> return 0;
> }
>
> /*
> * Check quota for allocation of this block.
> */
> if (DQUOT_ALLOC_BLOCK(inode, num)) {
> *errp = -EDQUOT;
> return 0;
> }
>
> sbi = EXT2_SB(sb);
> es = EXT2_SB(sb)->s_es;
> ext2_debug("goal=%lu.\n", goal);
>
> if (!ext2_has_free_blocks(sbi)) {
> *errp = -ENOSPC;
> goto out;
> }
>
> goal = ext2_group_first_block_no(sb,EXT2_I(inode)->i_block_group);
>
> for(fs_bg = 0; fs_bg < fs_bg_range_count; fs_bg++)
> {
> bg_start = bg_range[fs_bg].bg_start;
> bg_end = bg_range[fs_bg].bg_end;
>
> group_no = bg_start;
> goal_group = bg_start;
>
> retry_alloc:
>
> ngroups = (bg_end - bg_start) + 1;
> smp_rmb();
>
> /*
> * Now search the rest of the groups. We assume that
> * group_no and gdp correctly point to the last group visited.
> */
>
> for (bgi = 0; bgi < ngroups; bgi++, group_no++) {
> if (group_no > bg_end) /* ngroups */
> group_no = bg_start; /* previous value 0 */
> gdp = ext2_get_group_desc(sb, group_no, &gdp_bh);
> if (!gdp)
> goto io_error;
>
> free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
> /*
> * skip this group if the number of
> * free blocks is less than half of the reservation
> * window size.
> */
> if (free_blocks <= (windowsz/2))
> continue;
>
> brelse(bitmap_bh);
> bitmap_bh = read_block_bitmap(sb, group_no);
> if (!bitmap_bh)
> goto io_error;
> /*
> * try to allocate block(s) from this group, without a goal(-1).
> */
> grp_alloc_blk = ext2_try_to_allocate_with_rsv(sb, group_no,
> bitmap_bh, -1, my_rsv, &num);
> if (grp_alloc_blk >= 0)
> goto allocated;
> }
> }
> /*
> * We may end up a bogus ealier ENOSPC error due to
> * filesystem is "full" of reservations, but
> * there maybe indeed free blocks avaliable on disk
> * In this case, we just forget about the reservations
> * just do block allocation as without reservations.
> */
> if (my_rsv) {
> my_rsv = NULL;
> windowsz = 0;
> group_no = goal_group;
> goto retry_alloc;
> }
> /* No space left on the device */
> *errp = -ENOSPC;
> goto out;
>
> allocated:
>
> ext2_debug("using block group %d(%d)\n",
> group_no, gdp->bg_free_blocks_count);
>
> ret_block = grp_alloc_blk + ext2_group_first_block_no(sb, group_no);
>
> if (in_range(le32_to_cpu(gdp->bg_block_bitmap), ret_block, num) ||
> in_range(le32_to_cpu(gdp->bg_inode_bitmap), ret_block, num) ||
> in_range(ret_block, le32_to_cpu(gdp->bg_inode_table),
> EXT2_SB(sb)->s_itb_per_group) ||
> in_range(ret_block + num - 1, le32_to_cpu(gdp->bg_inode_table),
> EXT2_SB(sb)->s_itb_per_group)) {
> ext2_error(sb, "ext2_new_blocks",
> "Allocating block in system zone - "
> "blocks from "E2FSBLK", length %lu",
> ret_block, num);
> /*
> * ext2_try_to_allocate marked the blocks we allocated as in
> * use. So we may want to selectively mark some of the blocks
> * as free
> */
> goto retry_alloc;
> }
>
> performed_allocation = 1;
>
> if (ret_block + num - 1 >= le32_to_cpu(es->s_blocks_count)) {
> ext2_error(sb, "ext2_new_blocks",
> "block("E2FSBLK") >= blocks count(%d) - "
> "block_group = %d, es == %p ", ret_block,
> le32_to_cpu(es->s_blocks_count), group_no, es);
> goto out;
> }
>
> group_adjust_blocks(sb, group_no, gdp, gdp_bh, -num);
> percpu_counter_sub(&sbi->s_freeblocks_counter, num);
>
> mark_buffer_dirty(bitmap_bh);
> if (sb->s_flags & MS_SYNCHRONOUS)
> sync_dirty_buffer(bitmap_bh);
>
> *errp = 0;
> brelse(bitmap_bh);
> DQUOT_FREE_BLOCK(inode, *count-num);
> *count = num;
> return ret_block;
> io_error:
> *errp = -EIO;
> out:
> /*
> * Undo the block allocation
> */
> if (!performed_allocation)
> DQUOT_FREE_BLOCK(inode, *count);
> brelse(bitmap_bh);
> return 0;
> }
> EXPORT_SYMBOL(fs_bg_ext2_new_blocks);
This works fine.
I would surely like to see a similar ABI in the linux kernel soon.
> Regards,
> Akira Fujita
>
> --Separator@...ujita@...jp.nec.com:
> greg.freemyer@...il.com
> haanjdj@...il.com
> sandeepksinha@...il.com
> linux-ext4@...r.kernel.org
>
--
Regards,
Sandeep.
"To learn is to change. Education is a process that changes the learner."
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