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Date: Tue, 03 May 2011 17:12:28 -0700
From: Mingming Cao <cmm@...ibm.com>
To: Allison Henderson <achender@...ux.vnet.ibm.com>
Cc: Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [Ext4 punch hole 4/5 v6] Ext4 Punch Hole Support: Map blocks
punch hole flag
On Tue, 2011-05-03 at 09:48 -0700, Allison Henderson 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.
>
Just want to make sure that in the case of ENOSPC, the reserved root
blocks are used/consumed to allow extent being splitted and then punch
hole being proceeded. The reserved blocks, if I understand right, is
being used, not returned back. No?
Mingming
> The routine then returns the number of blocks successfully
> punched out.
>
> Signed-off-by: Allison Henderson <achender@...ibm.com>
> ---
> :100644 100644 0afb746... 7f0fcc1... M fs/ext4/extents.c
> fs/ext4/extents.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++------
> 1 files changed, 87 insertions(+), 11 deletions(-)
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 0afb746..7f0fcc1 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -3290,15 +3290,19 @@ 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) {
> /*
> @@ -3363,16 +3367,84 @@ 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_split_extent(handle, inode,
> + path, &punch_map, 0,
> + EXT4_GET_BLOCKS_PUNCH_OUT_EXT |
> + EXT4_GET_BLOCKS_PRE_IO);
> +
> + 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);
> +
> + err = ext4_ext_remove_space(inode, map->m_lblk,
> + map->m_lblk + punched_out);
> +
> + goto out2;
> }
> }
>
> @@ -3517,7 +3589,11 @@ 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)
--
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