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Date: Wed, 27 Mar 2013 18:01:59 +0100
From: Jan Kara <jack@...e.cz>
To: Theodore Ts'o <tytso@....edu>
Cc: Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 3/7] ext4: fold ext4_alloc_blocks() in
ext4_alloc_branch()
On Sun 24-03-13 20:06:50, Ted Tso wrote:
> The older code was far more complicated than it needed to be because
> of how we spliced in the ext4's new multiblock allocator into ext3's
> indirect block code. By folding ext4_alloc_blocks() into
> ext4_alloc_branch(), we make the code far more understable, shave off
> over 130 lines of code and half a kilobyte of compiled object code.
>
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>
The patch looks good. You can add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
> ---
> fs/ext4/indirect.c | 227 +++++++++++------------------------------------------
> 1 file changed, 46 insertions(+), 181 deletions(-)
>
> diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
> index b505a14..b780c4a 100644
> --- a/fs/ext4/indirect.c
> +++ b/fs/ext4/indirect.c
> @@ -292,131 +292,6 @@ static int ext4_blks_to_allocate(Indirect *branch, int k, unsigned int blks,
> }
>
> /**
> - * ext4_alloc_blocks: multiple allocate blocks needed for a branch
> - * @handle: handle for this transaction
> - * @inode: inode which needs allocated blocks
> - * @iblock: the logical block to start allocated at
> - * @goal: preferred physical block of allocation
> - * @indirect_blks: the number of blocks need to allocate for indirect
> - * blocks
> - * @blks: number of desired blocks
> - * @new_blocks: on return it will store the new block numbers for
> - * the indirect blocks(if needed) and the first direct block,
> - * @err: on return it will store the error code
> - *
> - * This function will return the number of blocks allocated as
> - * requested by the passed-in parameters.
> - */
> -static int ext4_alloc_blocks(handle_t *handle, struct inode *inode,
> - ext4_lblk_t iblock, ext4_fsblk_t goal,
> - int indirect_blks, int blks,
> - ext4_fsblk_t new_blocks[4], int *err)
> -{
> - struct ext4_allocation_request ar;
> - int target, i;
> - unsigned long count = 0, blk_allocated = 0;
> - int index = 0;
> - ext4_fsblk_t current_block = 0;
> - int ret = 0;
> -
> - /*
> - * Here we try to allocate the requested multiple blocks at once,
> - * on a best-effort basis.
> - * To build a branch, we should allocate blocks for
> - * the indirect blocks(if not allocated yet), and at least
> - * the first direct block of this branch. That's the
> - * minimum number of blocks need to allocate(required)
> - */
> - /* first we try to allocate the indirect blocks */
> - target = indirect_blks;
> - while (target > 0) {
> - count = target;
> - /* allocating blocks for indirect blocks and direct blocks */
> - current_block = ext4_new_meta_blocks(handle, inode, goal,
> - 0, &count, err);
> - if (*err)
> - goto failed_out;
> -
> - if (unlikely(current_block + count > EXT4_MAX_BLOCK_FILE_PHYS)) {
> - EXT4_ERROR_INODE(inode,
> - "current_block %llu + count %lu > %d!",
> - current_block, count,
> - EXT4_MAX_BLOCK_FILE_PHYS);
> - *err = -EIO;
> - goto failed_out;
> - }
> -
> - target -= count;
> - /* allocate blocks for indirect blocks */
> - while (index < indirect_blks && count) {
> - new_blocks[index++] = current_block++;
> - count--;
> - }
> - if (count > 0) {
> - /*
> - * save the new block number
> - * for the first direct block
> - */
> - new_blocks[index] = current_block;
> - WARN(1, KERN_INFO "%s returned more blocks than "
> - "requested\n", __func__);
> - break;
> - }
> - }
> -
> - target = blks - count ;
> - blk_allocated = count;
> - if (!target)
> - goto allocated;
> - /* Now allocate data blocks */
> - memset(&ar, 0, sizeof(ar));
> - ar.inode = inode;
> - ar.goal = goal;
> - ar.len = target;
> - ar.logical = iblock;
> - if (S_ISREG(inode->i_mode))
> - /* enable in-core preallocation only for regular files */
> - ar.flags = EXT4_MB_HINT_DATA;
> -
> - current_block = ext4_mb_new_blocks(handle, &ar, err);
> - if (unlikely(current_block + ar.len > EXT4_MAX_BLOCK_FILE_PHYS)) {
> - EXT4_ERROR_INODE(inode,
> - "current_block %llu + ar.len %d > %d!",
> - current_block, ar.len,
> - EXT4_MAX_BLOCK_FILE_PHYS);
> - *err = -EIO;
> - goto failed_out;
> - }
> -
> - if (*err && (target == blks)) {
> - /*
> - * if the allocation failed and we didn't allocate
> - * any blocks before
> - */
> - goto failed_out;
> - }
> - if (!*err) {
> - if (target == blks) {
> - /*
> - * save the new block number
> - * for the first direct block
> - */
> - new_blocks[index] = current_block;
> - }
> - blk_allocated += ar.len;
> - }
> -allocated:
> - /* total number of blocks allocated for direct blocks */
> - ret = blk_allocated;
> - *err = 0;
> - return ret;
> -failed_out:
> - for (i = 0; i < index; i++)
> - ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1, 0);
> - return ret;
> -}
> -
> -/**
> * ext4_alloc_branch - allocate and set up a chain of blocks.
> * @handle: handle for this transaction
> * @inode: owner
> @@ -448,60 +323,59 @@ static int ext4_alloc_branch(handle_t *handle, struct inode *inode,
> int *blks, ext4_fsblk_t goal,
> ext4_lblk_t *offsets, Indirect *branch)
> {
> - int blocksize = inode->i_sb->s_blocksize;
> - int i, n = 0;
> - int err = 0;
> - struct buffer_head *bh;
> - int num;
> - ext4_fsblk_t new_blocks[4];
> - ext4_fsblk_t current_block;
> + struct ext4_allocation_request ar;
> + struct buffer_head * bh;
> + ext4_fsblk_t b, new_blocks[4];
> + __le32 *p;
> + int i, j, err, len = 1;
>
> - num = ext4_alloc_blocks(handle, inode, iblock, goal, indirect_blks,
> - *blks, new_blocks, &err);
> - if (err)
> - return err;
> -
> - branch[0].key = cpu_to_le32(new_blocks[0]);
> /*
> - * metadata blocks and data blocks are allocated.
> + * Set up for the direct block allocation
> */
> - for (n = 1; n <= indirect_blks; n++) {
> - /*
> - * Get buffer_head for parent block, zero it out
> - * and set the pointer to new one, then send
> - * parent to disk.
> - */
> - bh = sb_getblk(inode->i_sb, new_blocks[n-1]);
> + memset(&ar, 0, sizeof(ar));
> + ar.inode = inode;
> + ar.len = *blks;
> + ar.logical = iblock;
> + if (S_ISREG(inode->i_mode))
> + ar.flags = EXT4_MB_HINT_DATA;
> +
> + for (i = 0; i <= indirect_blks; i++) {
> + if (i == indirect_blks) {
> + ar.goal = goal;
> + new_blocks[i] = ext4_mb_new_blocks(handle, &ar, &err);
> + } else
> + goal = new_blocks[i] = ext4_new_meta_blocks(handle, inode,
> + goal, 0, NULL, &err);
> + if (err) {
> + i--;
> + goto failed;
> + }
> + branch[i].key = cpu_to_le32(new_blocks[i]);
> + if (i == 0)
> + continue;
> +
> + bh = branch[i].bh = sb_getblk(inode->i_sb, new_blocks[i-1]);
> if (unlikely(!bh)) {
> err = -ENOMEM;
> goto failed;
> }
> -
> - branch[n].bh = bh;
> lock_buffer(bh);
> BUFFER_TRACE(bh, "call get_create_access");
> err = ext4_journal_get_create_access(handle, bh);
> if (err) {
> - /* Don't brelse(bh) here; it's done in
> - * ext4_journal_forget() below */
> unlock_buffer(bh);
> goto failed;
> }
>
> - memset(bh->b_data, 0, blocksize);
> - branch[n].p = (__le32 *) bh->b_data + offsets[n];
> - branch[n].key = cpu_to_le32(new_blocks[n]);
> - *branch[n].p = branch[n].key;
> - if (n == indirect_blks) {
> - current_block = new_blocks[n];
> - /*
> - * End of chain, update the last new metablock of
> - * the chain to point to the new allocated
> - * data blocks numbers
> - */
> - for (i = 1; i < num; i++)
> - *(branch[n].p + i) = cpu_to_le32(++current_block);
> - }
> + memset(bh->b_data, 0, bh->b_size);
> + p = branch[i].p = (__le32 *) bh->b_data + offsets[i];
> + b = new_blocks[i];
> +
> + if (i == indirect_blks)
> + len = ar.len;
> + for (j = 0; j < len; j++)
> + *p++ = cpu_to_le32(b++);
> +
> BUFFER_TRACE(bh, "marking uptodate");
> set_buffer_uptodate(bh);
> unlock_buffer(bh);
> @@ -511,25 +385,16 @@ static int ext4_alloc_branch(handle_t *handle, struct inode *inode,
> if (err)
> goto failed;
> }
> - *blks = num;
> - return err;
> + *blks = ar.len;
> + return 0;
> failed:
> - /* Allocation failed, free what we already allocated */
> - ext4_free_blocks(handle, inode, NULL, new_blocks[0], 1, 0);
> - for (i = 1; i <= n ; i++) {
> - /*
> - * branch[i].bh is newly allocated, so there is no
> - * need to revoke the block, which is why we don't
> - * need to set EXT4_FREE_BLOCKS_METADATA.
> - */
> - ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1,
> - EXT4_FREE_BLOCKS_FORGET);
> + for (; i >= 0; i--) {
> + if (i != indirect_blks && branch[i].bh)
> + ext4_forget(handle, 1, inode, branch[i].bh,
> + branch[i].bh->b_blocknr);
> + ext4_free_blocks(handle, inode, NULL, new_blocks[i],
> + (i == indirect_blks) ? ar.len : 1, 0);
> }
> - for (i = n+1; i < indirect_blks; i++)
> - ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1, 0);
> -
> - ext4_free_blocks(handle, inode, NULL, new_blocks[i], num, 0);
> -
> return err;
> }
>
> --
> 1.7.12.rc0.22.gcdd159b
>
> --
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--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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