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Date:	Tue, 19 Apr 2011 10:48:25 -0700
From:	Mingming Cao <cmm@...ibm.com>
To:	Yongqiang Yang <xiaoqiangnk@...il.com>
Cc:	Allison Henderson <achender@...ux.vnet.ibm.com>,
	linux-ext4@...r.kernel.org
Subject: Re: [Ext4 punch hole 5/6 v5] Ext4 Punch Hole Support: Map blocks
 punch hole flag

On Tue, 2011-04-19 at 16:35 +0800, 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?
> 

Looks like so, ext4_ext_map_blocks() takes journal handle as argument,
the ext4 punch hole code reserve the journal credits before calling
ext4_ext_map_blocks().


> > +
> > +                       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
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> > the body of a message to majordomo@...r.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >
> 
> 
> 


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