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Date: Mon, 7 Jan 2008 15:48:21 +0100
From: Jan Kara <jack@...e.cz>
To: marcin.slusarz@...il.com
Cc: LKML <linux-kernel@...r.kernel.org>,
Ben Fennema <bfennema@...con.csc.calpoly.edu>,
Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH 4/7] udf: replace loops coded with goto to real loops
On Sun 06-01-08 02:21:50, marcin.slusarz@...il.com wrote:
> Signed-off-by: Marcin Slusarz <marcin.slusarz@...il.com>
I'm not sure if this improves readability in general. If the code is
really a loop in nature, then we should code it using do {} while but in
case we loop back just in case of some error (as seems to be the case in
udf_bitmap_new_block()), then IMHO goto is more explanative. So at least
that one case I'd leave as is.
Honza
> ---
> fs/udf/balloc.c | 309 ++++++++++++++++++++++++++++---------------------------
> 1 files changed, 157 insertions(+), 152 deletions(-)
>
> diff --git a/fs/udf/balloc.c b/fs/udf/balloc.c
> index d1d4b8f..5ce7926 100644
> --- a/fs/udf/balloc.c
> +++ b/fs/udf/balloc.c
> @@ -183,46 +183,46 @@ static void udf_bitmap_free_blocks(struct super_block *sb,
> block = bloc.logicalBlockNum + offset +
> (sizeof(struct spaceBitmapDesc) << 3);
>
> -do_more:
> - overflow = 0;
> - block_group = block >> (sb->s_blocksize_bits + 3);
> - bit = block % (sb->s_blocksize << 3);
> + do {
> + overflow = 0;
> + block_group = block >> (sb->s_blocksize_bits + 3);
> + bit = block % (sb->s_blocksize << 3);
>
> - /*
> - * Check to see if we are freeing blocks across a group boundary.
> - */
> - if (bit + count > (sb->s_blocksize << 3)) {
> - overflow = bit + count - (sb->s_blocksize << 3);
> - count -= overflow;
> - }
> - bitmap_nr = load_block_bitmap(sb, bitmap, block_group);
> - if (bitmap_nr < 0)
> - goto error_return;
> + /*
> + * Check to see if we are freeing blocks across a group boundary.
> + */
> + if (bit + count > (sb->s_blocksize << 3)) {
> + overflow = bit + count - (sb->s_blocksize << 3);
> + count -= overflow;
> + }
> + bitmap_nr = load_block_bitmap(sb, bitmap, block_group);
> + if (bitmap_nr < 0)
> + goto error_return;
>
> - bh = bitmap->s_block_bitmap[bitmap_nr];
> - for (i = 0; i < count; i++) {
> - if (udf_set_bit(bit + i, bh->b_data)) {
> - udf_debug("bit %ld already set\n", bit + i);
> - udf_debug("byte=%2x\n",
> - ((char *)bh->b_data)[(bit + i) >> 3]);
> - } else {
> - if (inode)
> - DQUOT_FREE_BLOCK(inode, 1);
> - udf_inc_free_space(sbi, sbi->s_partition, 1);
> + bh = bitmap->s_block_bitmap[bitmap_nr];
> + for (i = 0; i < count; i++) {
> + if (udf_set_bit(bit + i, bh->b_data)) {
> + udf_debug("bit %ld already set\n", bit + i);
> + udf_debug("byte=%2x\n",
> + ((char *)bh->b_data)[(bit + i) >> 3]);
> + } else {
> + if (inode)
> + DQUOT_FREE_BLOCK(inode, 1);
> + udf_inc_free_space(sbi, sbi->s_partition, 1);
> + }
> }
> - }
> - mark_buffer_dirty(bh);
> - if (overflow) {
> - block += count;
> - count = overflow;
> - goto do_more;
> - }
> + mark_buffer_dirty(bh);
> + if (overflow) {
> + block += count;
> + count = overflow;
> + }
> + } while (overflow);
> +
> error_return:
> sb->s_dirt = 1;
> if (sbi->s_lvid_bh)
> mark_buffer_dirty(sbi->s_lvid_bh);
> mutex_unlock(&sbi->s_alloc_mutex);
> - return;
> }
>
> static int udf_bitmap_prealloc_blocks(struct super_block *sb,
> @@ -246,39 +246,40 @@ static int udf_bitmap_prealloc_blocks(struct super_block *sb,
> if (first_block + block_count > part_len)
> block_count = part_len - first_block;
>
> -repeat:
> - nr_groups = (sbi->s_partmaps[partition].s_partition_len +
> - (sizeof(struct spaceBitmapDesc) << 3) +
> - (sb->s_blocksize * 8) - 1) / (sb->s_blocksize * 8);
> - block = first_block + (sizeof(struct spaceBitmapDesc) << 3);
> - block_group = block >> (sb->s_blocksize_bits + 3);
> - group_start = block_group ? 0 : sizeof(struct spaceBitmapDesc);
> + do {
> + nr_groups = (sbi->s_partmaps[partition].s_partition_len +
> + (sizeof(struct spaceBitmapDesc) << 3) +
> + (sb->s_blocksize * 8) - 1) / (sb->s_blocksize * 8);
> + block = first_block + (sizeof(struct spaceBitmapDesc) << 3);
> + block_group = block >> (sb->s_blocksize_bits + 3);
> + group_start = block_group ? 0 : sizeof(struct spaceBitmapDesc);
>
> - bitmap_nr = load_block_bitmap(sb, bitmap, block_group);
> - if (bitmap_nr < 0)
> - goto out;
> - bh = bitmap->s_block_bitmap[bitmap_nr];
> + bitmap_nr = load_block_bitmap(sb, bitmap, block_group);
> + if (bitmap_nr < 0)
> + goto out;
> + bh = bitmap->s_block_bitmap[bitmap_nr];
>
> - bit = block % (sb->s_blocksize << 3);
> + bit = block % (sb->s_blocksize << 3);
>
> - while (bit < (sb->s_blocksize << 3) && block_count > 0) {
> - if (!udf_test_bit(bit, bh->b_data)) {
> - goto out;
> - } else if (DQUOT_PREALLOC_BLOCK(inode, 1)) {
> - goto out;
> - } else if (!udf_clear_bit(bit, bh->b_data)) {
> - udf_debug("bit already cleared for block %d\n", bit);
> - DQUOT_FREE_BLOCK(inode, 1);
> - goto out;
> + while (bit < (sb->s_blocksize << 3) && block_count > 0) {
> + if (!udf_test_bit(bit, bh->b_data))
> + goto out;
> + else if (DQUOT_PREALLOC_BLOCK(inode, 1))
> + goto out;
> + else if (!udf_clear_bit(bit, bh->b_data)) {
> + udf_debug("bit already cleared for block %d\n",
> + bit);
> + DQUOT_FREE_BLOCK(inode, 1);
> + goto out;
> + }
> + block_count--;
> + alloc_count++;
> + bit++;
> + block++;
> }
> - block_count--;
> - alloc_count++;
> - bit++;
> - block++;
> - }
> - mark_buffer_dirty(bh);
> - if (block_count > 0)
> - goto repeat;
> + mark_buffer_dirty(bh);
> + } while (block_count > 0);
> +
> out:
> if (udf_inc_free_space(sbi, partition, -alloc_count))
> mark_buffer_dirty(sbi->s_lvid_bh);
> @@ -298,117 +299,121 @@ static int udf_bitmap_new_block(struct super_block *sb,
> struct buffer_head *bh = NULL;
> char *ptr;
> int newblock = 0;
> + bool bit_already_cleared;
>
> *err = -ENOSPC;
> mutex_lock(&sbi->s_alloc_mutex);
>
> -repeat:
> - if (goal < 0 || goal >= sbi->s_partmaps[partition].s_partition_len)
> - goal = 0;
> -
> - nr_groups = bitmap->s_nr_groups;
> - block = goal + (sizeof(struct spaceBitmapDesc) << 3);
> - block_group = block >> (sb->s_blocksize_bits + 3);
> - group_start = block_group ? 0 : sizeof(struct spaceBitmapDesc);
> -
> - bitmap_nr = load_block_bitmap(sb, bitmap, block_group);
> - if (bitmap_nr < 0)
> - goto error_return;
> - bh = bitmap->s_block_bitmap[bitmap_nr];
> - ptr = memscan((char *)bh->b_data + group_start, 0xFF,
> - sb->s_blocksize - group_start);
> -
> - if ((ptr - ((char *)bh->b_data)) < sb->s_blocksize) {
> - bit = block % (sb->s_blocksize << 3);
> - if (udf_test_bit(bit, bh->b_data))
> - goto got_block;
> -
> - end_goal = (bit + 63) & ~63;
> - bit = udf_find_next_one_bit(bh->b_data, end_goal, bit);
> - if (bit < end_goal)
> - goto got_block;
> -
> - ptr = memscan((char *)bh->b_data + (bit >> 3), 0xFF,
> - sb->s_blocksize - ((bit + 7) >> 3));
> - newbit = (ptr - ((char *)bh->b_data)) << 3;
> - if (newbit < sb->s_blocksize << 3) {
> - bit = newbit;
> - goto search_back;
> - }
> -
> - newbit = udf_find_next_one_bit(bh->b_data,
> - sb->s_blocksize << 3, bit);
> - if (newbit < sb->s_blocksize << 3) {
> - bit = newbit;
> - goto got_block;
> - }
> - }
> + do {
> + if (goal < 0 ||
> + goal >= sbi->s_partmaps[partition].s_partition_len)
> + goal = 0;
>
> - for (i = 0; i < (nr_groups * 2); i++) {
> - block_group++;
> - if (block_group >= nr_groups)
> - block_group = 0;
> + nr_groups = bitmap->s_nr_groups;
> + block = goal + (sizeof(struct spaceBitmapDesc) << 3);
> + block_group = block >> (sb->s_blocksize_bits + 3);
> group_start = block_group ? 0 : sizeof(struct spaceBitmapDesc);
>
> bitmap_nr = load_block_bitmap(sb, bitmap, block_group);
> if (bitmap_nr < 0)
> goto error_return;
> bh = bitmap->s_block_bitmap[bitmap_nr];
> - if (i < nr_groups) {
> - ptr = memscan((char *)bh->b_data + group_start, 0xFF,
> - sb->s_blocksize - group_start);
> - if ((ptr - ((char *)bh->b_data)) < sb->s_blocksize) {
> - bit = (ptr - ((char *)bh->b_data)) << 3;
> - break;
> + ptr = memscan(bh->b_data + group_start, 0xFF,
> + sb->s_blocksize - group_start);
> +
> + if ((ptr - bh->b_data) < sb->s_blocksize) {
> + bit = block % (sb->s_blocksize << 3);
> + if (udf_test_bit(bit, bh->b_data))
> + goto got_block;
> +
> + end_goal = (bit + 63) & ~63;
> + bit = udf_find_next_one_bit(bh->b_data, end_goal, bit);
> + if (bit < end_goal)
> + goto got_block;
> +
> + ptr = memscan(bh->b_data + (bit >> 3), 0xFF,
> + sb->s_blocksize - ((bit + 7) >> 3));
> + newbit = (ptr - bh->b_data) << 3;
> + if (newbit < sb->s_blocksize << 3) {
> + bit = newbit;
> + goto search_back;
> + }
> +
> + newbit = udf_find_next_one_bit(bh->b_data,
> + sb->s_blocksize << 3, bit);
> + if (newbit < sb->s_blocksize << 3) {
> + bit = newbit;
> + goto got_block;
> }
> - } else {
> - bit = udf_find_next_one_bit((char *)bh->b_data,
> - sb->s_blocksize << 3,
> - group_start << 3);
> - if (bit < sb->s_blocksize << 3)
> - break;
> }
> - }
> - if (i >= (nr_groups * 2)) {
> - mutex_unlock(&sbi->s_alloc_mutex);
> - return newblock;
> - }
> - if (bit < sb->s_blocksize << 3)
> - goto search_back;
> - else
> - bit = udf_find_next_one_bit(bh->b_data, sb->s_blocksize << 3,
> - group_start << 3);
> - if (bit >= sb->s_blocksize << 3) {
> - mutex_unlock(&sbi->s_alloc_mutex);
> - return 0;
> - }
> +
> + for (i = 0; i < (nr_groups * 2); i++) {
> + block_group++;
> + if (block_group >= nr_groups)
> + block_group = 0;
> + group_start = block_group ?
> + 0 : sizeof(struct spaceBitmapDesc);
> +
> + bitmap_nr = load_block_bitmap(sb, bitmap, block_group);
> + if (bitmap_nr < 0)
> + goto error_return;
> + bh = bitmap->s_block_bitmap[bitmap_nr];
> + if (i < nr_groups) {
> + ptr = memscan(bh->b_data + group_start,
> + 0xFF, sb->s_blocksize - group_start);
> + if ((ptr - bh->b_data) < sb->s_blocksize) {
> + bit = (ptr - bh->b_data) << 3;
> + break;
> + }
> + } else {
> + bit = udf_find_next_one_bit(bh->b_data,
> + sb->s_blocksize << 3,
> + group_start << 3);
> + if (bit < sb->s_blocksize << 3)
> + break;
> + }
> + }
> + if (i >= (nr_groups * 2)) {
> + mutex_unlock(&sbi->s_alloc_mutex);
> + return newblock;
> + }
> + if (bit < sb->s_blocksize << 3)
> + goto search_back;
> + else
> + bit = udf_find_next_one_bit(bh->b_data,
> + sb->s_blocksize << 3,
> + group_start << 3);
> + if (bit >= sb->s_blocksize << 3) {
> + mutex_unlock(&sbi->s_alloc_mutex);
> + return 0;
> + }
>
> search_back:
> - i = 0;
> - while (i < 7 && bit > (group_start << 3) &&
> - udf_test_bit(bit - 1, bh->b_data)) {
> - ++i;
> - --bit;
> - }
> + i = 0;
> + while (i < 7 && bit > (group_start << 3) &&
> + udf_test_bit(bit - 1, bh->b_data)) {
> + ++i;
> + --bit;
> + }
>
> got_block:
>
> - /*
> - * Check quota for allocation of this block.
> - */
> - if (inode && DQUOT_ALLOC_BLOCK(inode, 1)) {
> - mutex_unlock(&sbi->s_alloc_mutex);
> - *err = -EDQUOT;
> - return 0;
> - }
> + /*
> + * Check quota for allocation of this block.
> + */
> + if (inode && DQUOT_ALLOC_BLOCK(inode, 1)) {
> + mutex_unlock(&sbi->s_alloc_mutex);
> + *err = -EDQUOT;
> + return 0;
> + }
>
> - newblock = bit + (block_group << (sb->s_blocksize_bits + 3)) -
> - (sizeof(struct spaceBitmapDesc) << 3);
> + newblock = bit + (block_group << (sb->s_blocksize_bits + 3)) -
> + (sizeof(struct spaceBitmapDesc) << 3);
>
> - if (!udf_clear_bit(bit, bh->b_data)) {
> - udf_debug("bit already cleared for block %d\n", bit);
> - goto repeat;
> - }
> + bit_already_cleared = !udf_clear_bit(bit, bh->b_data);
> + if (bit_already_cleared)
> + udf_debug("bit already cleared for block %d\n", bit);
> + } while (bit_already_cleared);
>
> mark_buffer_dirty(bh);
>
> --
> 1.5.3.7
>
--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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