On Wed, 24 Nov 2010, Jan Kara wrote:
> From: Lukas Czerner <lczerner@xxxxxxxxxx>
>
> Walk through allocation groups and trim all free extents. It can be
> invoked through FITRIM ioctl on the file system. The main idea is to
> provide a way to trim the whole file system if needed, since some SSD's
> may suffer from performance loss after the whole device was filled (it
> does not mean that fs is full!).
>
> It search for free extents in allocation groups specified by Byte range
> start -> start+len. When the free extent is within this range, blocks are
> marked as used and then trimmed. Afterwards these blocks are marked as
> free in per-group bitmap.
>
> [JK: Fixed up error handling]
>
> Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
> Reviewed-by: Jan Kara <jack@xxxxxxx>
> Reviewed-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
> fs/ext3/balloc.c | 257 +++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/ext3_fs.h | 1 +
> 2 files changed, 258 insertions(+), 0 deletions(-)
>
> diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
> index b3db226..ae88960 100644
> --- a/fs/ext3/balloc.c
> +++ b/fs/ext3/balloc.c
> @@ -20,6 +20,7 @@
> #include <linux/ext3_jbd.h>
> #include <linux/quotaops.h>
> #include <linux/buffer_head.h>
> +#include <linux/blkdev.h>
>
> /*
> * balloc.c contains the blocks allocation and deallocation routines
> @@ -39,6 +40,23 @@
>
> #define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1)
>
> +/*
> + * Calculate the block group number and offset, given a block number
> + */
> +void ext3_get_group_no_and_offset(struct super_block *sb, ext3_fsblk_t blocknr,
> + unsigned long *blockgrpp, ext3_grpblk_t *offsetp)
> +{
> + struct ext3_super_block *es = EXT3_SB(sb)->s_es;
> + ext3_grpblk_t offset;
> +
> + blocknr = blocknr - le32_to_cpu(es->s_first_data_block);
> + offset = do_div(blocknr, EXT3_BLOCKS_PER_GROUP(sb));
> + if (offsetp)
> + *offsetp = offset;
> + if (blockgrpp)
> + *blockgrpp = blocknr;
> +}
> +
> /**
> * ext3_get_group_desc() -- load group descriptor from disk
> * @sb: super block
> @@ -1885,3 +1903,242 @@ unsigned long ext3_bg_num_gdb(struct super_block *sb, int group)
> return ext3_bg_num_gdb_meta(sb,group);
>
> }
> +
> +/**
> + * ext3_trim_all_free -- function to trim all free space in alloc. group
> + * @sb: super block for file system
> + * @group: allocation group to trim
> + * @start: first group block to examine
> + * @max: last group block to examine
> + * @gdp: allocation group description structure
> + * @minblocks: minimum extent block count
> + *
> + * ext3_trim_all_free walks through group's block bitmap searching for free
> + * blocks. When the free block is found, it tries to allocate this block and
> + * consequent free block to get the biggest free extent possible, until it
> + * reaches any used block. Then issue a TRIM command on this extent and free
> + * the extent in the block bitmap. This is done until whole group is scanned.
> + */
> +ext3_grpblk_t ext3_trim_all_free(struct super_block *sb, unsigned int group,
> + ext3_grpblk_t start, ext3_grpblk_t max,
> + ext3_grpblk_t minblocks)
> +{
> + handle_t *handle;
> + ext3_grpblk_t next, free_blocks, bit, freed, count = 0;
> + ext3_fsblk_t discard_block;
> + struct ext3_sb_info *sbi;
> + struct buffer_head *gdp_bh, *bitmap_bh = NULL;
> + struct ext3_group_desc *gdp;
> + int err = 0, ret = 0;
> +
> + /*
> + * We will update one block bitmap, and one group descriptor
> + */
> + handle = ext3_journal_start_sb(sb, 2);
> + if (IS_ERR(handle))
> + return PTR_ERR(handle);
> +
> + bitmap_bh = read_block_bitmap(sb, group);
> + if (!bitmap_bh) {
> + err = -EIO;
> + goto err_out;
> + }
> +
> + BUFFER_TRACE(bitmap_bh, "getting undo access");
> + err = ext3_journal_get_undo_access(handle, bitmap_bh);
> + if (err)
> + goto err_out;
> +
> + gdp = ext3_get_group_desc(sb, group, &gdp_bh);
> + if (!gdp) {
> + err = -EIO;
> + goto err_out;
> + }
> +
> + BUFFER_TRACE(gdp_bh, "get_write_access");
> + err = ext3_journal_get_write_access(handle, gdp_bh);
> + if (err)
> + goto err_out;
> +
> + free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
> + sbi = EXT3_SB(sb);
> +
> + /* Walk through the whole group */
> + while (start < max) {
> + start = bitmap_search_next_usable_block(start, bitmap_bh, max);
> + if (start < 0)
> + break;
> + next = start;
> +
> + /*
> + * Allocate contiguous free extents by setting bits in the
> + * block bitmap
> + */
> + while (next < max
> + && claim_block(sb_bgl_lock(sbi, group),
> + next, bitmap_bh)) {
> + next++;
> + }
> +
> + /* We did not claim any blocks */
> + if (next == start)
> + continue;
> +
> + discard_block = (ext3_fsblk_t)start +
> + ext3_group_first_block_no(sb, group);
> +
> + /* Update counters */
> + spin_lock(sb_bgl_lock(sbi, group));
> + le16_add_cpu(&gdp->bg_free_blocks_count, start - next);
> + spin_unlock(sb_bgl_lock(sbi, group));
> + percpu_counter_sub(&sbi->s_freeblocks_counter, next - start);
> +
> + /* Do not issue a TRIM on extents smaller than minblocks */
> + if ((next - start) < minblocks)
> + goto free_extent;
> +
> + /* Send the TRIM command down to the device */
> + err = sb_issue_discard(sb, discard_block, next - start,
> + GFP_NOFS, 0);
> + count += (next - start);
> +free_extent:
> + freed = 0;
> +
> + /*
> + * Clear bits in the bitmap
> + */
> + for (bit = start; bit < next; bit++) {
> + BUFFER_TRACE(bitmap_bh, "clear bit");
> + if (!ext3_clear_bit_atomic(sb_bgl_lock(sbi, group),
> + bit, bitmap_bh->b_data)) {
> + ext3_error(sb, __func__,
> + "bit already cleared for block "E3FSBLK,
> + (unsigned long)bit);
> + BUFFER_TRACE(bitmap_bh, "bit already cleared");
> + } else {
> + freed++;
> + }
> + }
> +
> + /* Update couters */
> + spin_lock(sb_bgl_lock(sbi, group));
> + le16_add_cpu(&gdp->bg_free_blocks_count, freed);
> + spin_unlock(sb_bgl_lock(sbi, group));
> + percpu_counter_add(&sbi->s_freeblocks_counter, freed);
> +
> + start = next;
> + if (err < 0) {
> + if (err != -EOPNOTSUPP)
> + ext3_warning(sb, __func__, "Discard command "
> + "returned error %d\n", err);
> + break;
> + }
> +
> + if (fatal_signal_pending(current)) {
> + err = -ERESTARTSYS;
> + break;
> + }
> +
> + cond_resched();
> +
> + /* No more suitable extents */
> + if ((free_blocks - count) < minblocks)
> + break;
> + }
> +
> + /* We dirtied the bitmap block */
> + BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
> + err = ext3_journal_dirty_metadata(handle, bitmap_bh);
> +
> + /* And the group descriptor block */
> + BUFFER_TRACE(gdp_bh, "dirtied group descriptor block");
> + ret = ext3_journal_dirty_metadata(handle, gdp_bh);
> + if (!err)
> + err = ret;
> +
> + ext3_debug("trimmed %d blocks in the group %d\n",
> + count, group);
> +
> +err_out:
> + if (err)
> + count = err;
> + ext3_journal_stop(handle);
> + brelse(bitmap_bh);
> +
> + return count;
> +}
> +
> +/**
> + * ext3_trim_fs() -- trim ioctl handle function
> + * @sb: superblock for filesystem
> + * @start: First Byte to trim
> + * @len: number of Bytes to trim from start
> + * @minlen: minimum extent length in Bytes
> + *
> + * ext3_trim_fs goes through all allocation groups containing Bytes from
> + * start to start+len. For each such a group ext3_trim_all_free function
> + * is invoked to trim all free space.
> + */
> +int ext3_trim_fs(struct super_block *sb, struct fstrim_range *range)
> +{
> + ext3_grpblk_t last_block, first_block, free_blocks;
> + unsigned long first_group, last_group;
> + unsigned long group, ngroups;
> + struct ext3_group_desc *gdp;
> + struct ext3_super_block *es;
> + uint64_t start, len, minlen, trimmed;
> + int ret = 0;
We probably need to add this:
ext3_fsblk_t blocks_count = le32_to_cpu(EXT3_SB(sb)->s_es->s_blocks_count);
> +
> + start = range->start >> sb->s_blocksize_bits;
> + len = range->len >> sb->s_blocksize_bits;
> + minlen = range->minlen >> sb->s_blocksize_bits;
> + trimmed = 0;
and this:
if (len > blocks_count)
len = blocks_count - start;
Because when determining last group through ext3_get_group_no_and_offset()
the result may be wrong in cases when range->start and range-len are too
big, because it may overflow when summing up those two numbers.
> +
> + if (unlikely(minlen > EXT3_BLOCKS_PER_GROUP(sb)))
> + return -EINVAL;
> +
> + es = EXT3_SB(sb)->s_es;
> + ngroups = EXT3_SB(sb)->s_groups_count;
> + smp_rmb();
> +
> + /* Determine first and last group to examine based on start and len */
> + ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) start,
> + &first_group, &first_block);
> + ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) (start + len),
^^^^^^^^^^^^^
here
overflow may occur.
> + &last_group, &last_block);
> + last_group = (last_group > ngroups - 1) ? ngroups - 1 : last_group;
> + last_block = EXT3_BLOCKS_PER_GROUP(sb);
> +
> + if (first_group > last_group)
> + return -EINVAL;
> +
> + for (group = first_group; group <= last_group; group++) {
> + gdp = ext3_get_group_desc(sb, group, NULL);
> + if (!gdp)
> + break;
> +
> + free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
> + if (free_blocks < minlen)
> + continue;
> +
> + if (len >= EXT3_BLOCKS_PER_GROUP(sb))
> + len -= (EXT3_BLOCKS_PER_GROUP(sb) - first_block);
> + else
> + last_block = len;
> +
> + ret = ext3_trim_all_free(sb, group, first_block,
> + last_block, minlen);
> + if (ret < 0)
> + break;
> +
> + trimmed += ret;
> + first_block = 0;
> + }
> +
> + if (ret >= 0)
> + ret = 0;
> +
> + range->len = trimmed * sb->s_blocksize;
> +
> + return ret;
> +}
> diff --git a/include/linux/ext3_fs.h b/include/linux/ext3_fs.h
> index 6ce1bca..a443965 100644
> --- a/include/linux/ext3_fs.h
> +++ b/include/linux/ext3_fs.h
> @@ -856,6 +856,7 @@ extern struct ext3_group_desc * ext3_get_group_desc(struct super_block * sb,
> extern int ext3_should_retry_alloc(struct super_block *sb, int *retries);
> extern void ext3_init_block_alloc_info(struct inode *);
> extern void ext3_rsv_window_add(struct super_block *sb, struct ext3_reserve_window_node *rsv);
> +extern int ext3_trim_fs(struct super_block *sb, struct fstrim_range *range);
>
> /* dir.c */
> extern int ext3_check_dir_entry(const char *, struct inode *,
>
--
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