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Re: [PATCH] * grub-core/fs/ext2.c (grub_ext2_read_block): Factor out com
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From: |
Vladimir 'φ-coder/phcoder' Serbinenko |
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Subject: |
Re: [PATCH] * grub-core/fs/ext2.c (grub_ext2_read_block): Factor out common code for indirect block handling. |
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Date: |
Wed, 13 Nov 2013 18:58:14 +0100 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20131005 Icedove/17.0.9 |
On 13.11.2013 12:33, Colin Watson wrote:
> Saves 185 bytes on compressed image.
Go ahead.
> ---
> ChangeLog | 7 ++++
> grub-core/fs/ext2.c | 119
> +++++++++++++++++-----------------------------------
> 2 files changed, 45 insertions(+), 81 deletions(-)
>
> diff --git a/ChangeLog b/ChangeLog
> index 716f69c..4454fd8 100644
> --- a/ChangeLog
> +++ b/ChangeLog
> @@ -1,5 +1,12 @@
> 2013-11-13 Colin Watson <address@hidden>
>
> + * grub-core/fs/ext2.c (grub_ext2_read_block): Factor out common
> + code for indirect block handling.
> +
> + Saves 185 bytes on compressed image.
> +
> +2013-11-13 Colin Watson <address@hidden>
> +
> * util/grub-editenv.c (help_filter, argp): Document how to delete
> the whole environment block.
> Reported by Dan Jacobson. Fixes Debian bug #726265.
> diff --git a/grub-core/fs/ext2.c b/grub-core/fs/ext2.c
> index aba5cb1..5f7a2b9 100644
> --- a/grub-core/fs/ext2.c
> +++ b/grub-core/fs/ext2.c
> @@ -397,9 +397,12 @@ grub_ext2_read_block (grub_fshelp_node_t node,
> grub_disk_addr_t fileblock)
> {
> struct grub_ext2_data *data = node->data;
> struct grub_ext2_inode *inode = &node->inode;
> - grub_disk_addr_t blknr = -1;
> unsigned int blksz = EXT2_BLOCK_SIZE (data);
> + grub_disk_addr_t blksz_quarter = blksz / 4;
> int log2_blksz = LOG2_EXT2_BLOCK_SIZE (data);
> + int log_perblock = log2_blksz + 9 - 2;
> + grub_uint32_t indir;
> + int shift;
>
> if (inode->flags & grub_cpu_to_le32_compile_time (EXT4_EXTENTS_FLAG))
> {
> @@ -448,96 +451,50 @@ grub_ext2_read_block (grub_fshelp_node_t node,
> grub_disk_addr_t fileblock)
>
> return ret;
> }
> +
> /* Direct blocks. */
> if (fileblock < INDIRECT_BLOCKS)
> - blknr = grub_le_to_cpu32 (inode->blocks.dir_blocks[fileblock]);
> + return grub_le_to_cpu32 (inode->blocks.dir_blocks[fileblock]);
> + fileblock -= INDIRECT_BLOCKS;
> /* Indirect. */
> - else if (fileblock < INDIRECT_BLOCKS + blksz / 4)
> + if (fileblock < blksz_quarter)
> {
> - grub_uint32_t indir;
> -
> - if (grub_disk_read (data->disk,
> - ((grub_disk_addr_t)
> - grub_le_to_cpu32 (inode->blocks.indir_block))
> - << log2_blksz,
> - (fileblock - INDIRECT_BLOCKS) * sizeof (indir),
> - sizeof (indir), &indir))
> - return grub_errno;
> -
> - blknr = grub_le_to_cpu32 (indir);
> + indir = inode->blocks.indir_block;
> + shift = 0;
> + goto indirect;
> }
> + fileblock -= blksz_quarter;
> /* Double indirect. */
> - else if (fileblock < INDIRECT_BLOCKS
> - + blksz / 4 * ((grub_disk_addr_t) blksz / 4 + 1))
> + if (fileblock < blksz_quarter * blksz_quarter)
> {
> - int log_perblock = log2_blksz + 9 - 2;
> - grub_disk_addr_t rblock = fileblock - (INDIRECT_BLOCKS
> - + blksz / 4);
> - grub_uint32_t indir;
> -
> - if (grub_disk_read (data->disk,
> - ((grub_disk_addr_t)
> - grub_le_to_cpu32 (inode->blocks.double_indir_block))
> - << log2_blksz,
> - (rblock >> log_perblock) * sizeof (indir),
> - sizeof (indir), &indir))
> - return grub_errno;
> -
> - if (grub_disk_read (data->disk,
> - ((grub_disk_addr_t)
> - grub_le_to_cpu32 (indir))
> - << log2_blksz,
> - (rblock & ((1 << log_perblock) - 1)) * sizeof (indir),
> - sizeof (indir), &indir))
> - return grub_errno;
> -
> -
> - blknr = grub_le_to_cpu32 (indir);
> + indir = inode->blocks.double_indir_block;
> + shift = 1;
> + goto indirect;
> }
> - /* triple indirect. */
> - else if (fileblock < INDIRECT_BLOCKS + blksz / 4 * ((grub_disk_addr_t)
> blksz / 4 + 1)
> - + ((grub_disk_addr_t) blksz / 4) * ((grub_disk_addr_t) blksz / 4)
> - * ((grub_disk_addr_t) blksz / 4 + 1))
> + fileblock -= blksz_quarter * blksz_quarter;
> + /* Triple indirect. */
> + if (fileblock < blksz_quarter * blksz_quarter * (blksz_quarter + 1))
> {
> - int log_perblock = log2_blksz + 9 - 2;
> - grub_disk_addr_t rblock = fileblock - (INDIRECT_BLOCKS + blksz / 4
> - * (blksz / 4 + 1));
> - grub_uint32_t indir;
> -
> - if (grub_disk_read (data->disk,
> - ((grub_disk_addr_t)
> - grub_le_to_cpu32 (inode->blocks.triple_indir_block))
> - << log2_blksz,
> - ((rblock >> log_perblock) >> log_perblock)
> - * sizeof (indir), sizeof (indir), &indir))
> - return grub_errno;
> -
> - if (grub_disk_read (data->disk,
> - ((grub_disk_addr_t)
> - grub_le_to_cpu32 (indir))
> - << log2_blksz,
> - ((rblock >> log_perblock)
> - & ((1 << log_perblock) - 1)) * sizeof (indir),
> - sizeof (indir), &indir))
> - return grub_errno;
> -
> - if (grub_disk_read (data->disk,
> - ((grub_disk_addr_t)
> - grub_le_to_cpu32 (indir))
> - << log2_blksz,
> - (rblock & ((1 << log_perblock) - 1))
> - * sizeof (indir), sizeof (indir), &indir))
> - return grub_errno;
> -
> - blknr = grub_le_to_cpu32 (indir);
> + indir = inode->blocks.triple_indir_block;
> + shift = 2;
> + goto indirect;
> }
> - else
> - {
> - grub_error (GRUB_ERR_BAD_FS,
> - "ext2fs doesn't support quadruple indirect blocks");
> - }
> -
> - return blknr;
> + return grub_error (GRUB_ERR_BAD_FS,
> + "ext2fs doesn't support quadruple indirect blocks");
> +
> +indirect:
> + do {
> + if (grub_disk_read (data->disk,
> + ((grub_disk_addr_t) grub_le_to_cpu32 (indir))
> + << log2_blksz,
> + ((fileblock >> (log_perblock * shift))
> + & ((1 << log_perblock) - 1))
> + * sizeof (indir),
> + sizeof (indir), &indir))
> + return grub_errno;
> + } while (shift--);
> +
> + return grub_le_to_cpu32 (indir);
> }
>
> /* Read LEN bytes from the file described by DATA starting with byte
>
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