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Date:	Tue, 19 Apr 2011 10:48:36 -0700
From:	Allison Henderson <achender@...ux.vnet.ibm.com>
To:	Yongqiang Yang <xiaoqiangnk@...il.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 4/19/2011 1:35 AM, Yongqiang Yang wrote:
> 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?
Hi there, 

Yes, the ext4_ext_map_blocks routine requires a journal handle as a parameter, so the calling function is required to set up the journal.

> 
>> +
>> +                       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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>>
> 
> 
> 

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