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Date:	Tue, 19 Apr 2011 16:35:48 +0800
From:	Yongqiang Yang <xiaoqiangnk@...il.com>
To:	Allison Henderson <achender@...ux.vnet.ibm.com>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [Ext4 punch hole 5/6 v5] Ext4 Punch Hole Support: Map blocks
 punch hole flag

On Tue, Apr 19, 2011 at 3:43 PM, Allison Henderson
<achender@...ux.vnet.ibm.com> wrote:
> This patch adds a new flag to map blocks that specifies
> the given range of blocks should be punched out.  Extents
> are first converted to uninitialized extents before they are
> punched out. Because punching a hole may require that the
> extent be split, it is possible that the splitting may need
> more blocks than are available.  To deal with this, reserved
> blocks are temporarily borrowed to allow the split to proceed.
> The borrowed blocks are then returned after the hole punch has
> released more blocks.
>
> The routine then returns the number of blocks successfully
> punched out.
>
> Signed-off-by: Allison Henderson <achender@...ibm.com>
> ---
> :100644 100644 e3a721a... d97bc87... M  fs/ext4/extents.c
>  fs/ext4/extents.c |   99 +++++++++++++++++++++++++++++++++++++++++++++++------
>  1 files changed, 88 insertions(+), 11 deletions(-)
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index e3a721a..d97bc87 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -3456,15 +3456,19 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
>        ext4_fsblk_t newblock = 0;
>        int err = 0, depth, ret;
>        unsigned int allocated = 0;
> +       unsigned int punched_out = 0;
> +       unsigned int result = 0;
>        struct ext4_allocation_request ar;
>        ext4_io_end_t *io = EXT4_I(inode)->cur_aio_dio;
> +       struct ext4_map_blocks punch_map;
>
>        ext_debug("blocks %u/%u requested for inode %lu\n",
>                  map->m_lblk, map->m_len, inode->i_ino);
>        trace_ext4_ext_map_blocks_enter(inode, map->m_lblk, map->m_len, flags);
>
>        /* check in cache */
> -       if (ext4_ext_in_cache(inode, map->m_lblk, &newex)) {
> +       if (ext4_ext_in_cache(inode, map->m_lblk, &newex) &&
> +               ((flags & EXT4_GET_BLOCKS_PUNCH_OUT_EXT) == 0)) {
>                if (!newex.ee_start_lo && !newex.ee_start_hi) {
>                        if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {
>                                /*
> @@ -3529,16 +3533,85 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
>                        ext_debug("%u fit into %u:%d -> %llu\n", map->m_lblk,
>                                  ee_block, ee_len, newblock);
>
> -                       /* Do not put uninitialized extent in the cache */
> -                       if (!ext4_ext_is_uninitialized(ex)) {
> -                               ext4_ext_put_in_cache(inode, ee_block,
> -                                                       ee_len, ee_start);
> -                               goto out;
> +                       if ((flags & EXT4_GET_BLOCKS_PUNCH_OUT_EXT) == 0) {
> +                               /*
> +                                * Do not put uninitialized extent
> +                                * in the cache
> +                                */
> +                               if (!ext4_ext_is_uninitialized(ex)) {
> +                                       ext4_ext_put_in_cache(inode, ee_block,
> +                                               ee_len, ee_start);
> +                                       goto out;
> +                               }
> +                               ret = ext4_ext_handle_uninitialized_extents(
> +                                       handle, inode, map, path, flags,
> +                                       allocated, newblock);
> +                               return ret;
>                        }
> -                       ret = ext4_ext_handle_uninitialized_extents(handle,
> -                                       inode, map, path, flags, allocated,
> -                                       newblock);
> -                       return ret;
> +
> +                       /*
> +                        * Punch out the map length, but only to the
> +                        * end of the extent
> +                        */
> +                       punched_out = allocated < map->m_len ?
> +                               allocated : map->m_len;
> +
> +                       /*
> +                        * Sense extents need to be converted to
> +                        * uninitialized, they must fit in an
> +                        * uninitialized extent
> +                        */
> +                       if (punched_out > EXT_UNINIT_MAX_LEN)
> +                               punched_out = EXT_UNINIT_MAX_LEN;
> +
> +                       punch_map.m_lblk = map->m_lblk;
> +                       punch_map.m_pblk = newblock;
> +                       punch_map.m_len = punched_out;
> +                       punch_map.m_flags = 0;
> +
> +                       /* Check to see if the extent needs to be split */
> +                       if (punch_map.m_len != ee_len ||
> +                               punch_map.m_lblk != ee_block) {
> +
> +                               ret = ext4_ext_split_extents(handle, inode,
> +                               &punch_map, path,
> +                               EXT4_GET_BLOCKS_PRE_IO |
> +                               EXT4_HAS_FREE_BLKS_USE_ROOTBLKS,
> +                               0);
> +
> +                               if (ret < 0) {
> +                                       err = ret;
> +                                       goto out2;
> +                               }
> +                               /*
> +                                * find extent for the block at
> +                                * the start of the hole
> +                                */
> +                               ext4_ext_drop_refs(path);
> +                               kfree(path);
> +
> +                               path = ext4_ext_find_extent(inode,
> +                               map->m_lblk, NULL);
> +                               if (IS_ERR(path)) {
> +                                       err = PTR_ERR(path);
> +                                       path = NULL;
> +                                       goto out2;
> +                               }
> +
> +                               depth = ext_depth(inode);
> +                               ex = path[depth].p_ext;
> +                               ee_len = ext4_ext_get_actual_len(ex);
> +                               ee_block = le32_to_cpu(ex->ee_block);
> +                               ee_start = ext4_ext_pblock(ex);
> +
> +                       }
> +
> +                       ext4_ext_mark_uninitialized(ex);
Is this change journaled?

> +
> +                       err = ext4_ext_remove_space(inode, map->m_lblk,
> +                               map->m_lblk + punched_out);
> +
> +                       goto out2;
>                }
>        }
>
> @@ -3683,7 +3756,11 @@ out2:
>        }
>        trace_ext4_ext_map_blocks_exit(inode, map->m_lblk,
>                newblock, map->m_len, err ? err : allocated);
> -       return err ? err : allocated;
> +
> +       result = (flags & EXT4_GET_BLOCKS_PUNCH_OUT_EXT) ?
> +                       punched_out : allocated;
> +
> +       return err ? err : result;
>  }
>
>  void ext4_ext_truncate(struct inode *inode)
> --
> 1.7.1
>
> --
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-- 
Best Wishes
Yongqiang Yang
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