From: Yongqiang Yang <xiaoqiangnk@gmail.com>
Subject: Re: [Ext4 punch hole 4/5] Ext4 Punch Hole Support: Enable Punch Hole
Date: Wed, 2 Mar 2011 14:21:22 +0800
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Cc: Allison Henderson <achender@linux.vnet.ibm.com>,
	linux-ext4@vger.kernel.org
To: Mingming Cao <cmm@us.ibm.com>
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On Wed, Mar 2, 2011 at 10:34 AM, Yongqiang Yang <xiaoqiangnk@gmail.com>=
 wrote:
> On Wed, Mar 2, 2011 at 9:49 AM, Mingming Cao <cmm@us.ibm.com> wrote:
>> On Mon, 2011-02-28 at 20:09 -0700, Allison Henderson wrote:
>>> This patch adds the =A0new "ext4_punch_hole" "ext4_ext_punch_hole" =
routines.
>>>
>>> fallocate has been modified to call ext4_punch_hole when the punch =
hole
>>> flag is passed. =A0At the moment, we only support punching holes in
>>> extents, so this routine is pretty much a wrapper for the ext4_ext_=
punch_hole
>>> routine.
>>>
>>> The ext4_ext_punch_hole routine zeros out the pages that are
>>> covered by the hole. =A0The blocks to be punched out
>>> are then identified as mapped, delayed, or already punched out.
>>> The blocks that mapped are the converted to into uninitialized
>>> extents. =A0The blocks are then punched out using the
>>> "ext4_ext_release_blocks" routine.
>>>
>>
>> All right, I mainly looked at the punch hole over a hole or delayed
>> allocation handling part...so my comments below...
>>
>>> Some minor utility functions have also been added.
>>> A new ext4_ext_lookup_hole routine is used by
>>> ext4_ext_punch_hole to check if a range of blocks
>>> have already been punched out.
>>>
>>> A new ext4_ext_test_block_flag has also been
>>> added to identify the state of a block (ie mapped,
>>> delayed, ect)
>>>
>>> Signed-off-by: Allison Henderson <achender@us.ibm.com>
>>> ---
>>> :100644 100644 43a5772... aeb86d6... M =A0 =A0 =A0 =A0fs/ext4/ext4.=
h
>>> :100644 100644 efbc3ef... 5713258... M =A0 =A0 =A0 =A0fs/ext4/exten=
ts.c
>>> :100644 100644 28c9137... 493c908... M =A0 =A0 =A0 =A0fs/ext4/inode=
=2Ec
>>> =A0fs/ext4/ext4.h =A0 =A0| =A0 =A02 +
>>> =A0fs/ext4/extents.c | =A0321 +++++++++++++++++++++++++++++++++++++=
+++++++++++++++-
>>> =A0fs/ext4/inode.c =A0 | =A0 26 +++++
>>> =A03 files changed, 345 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
>>> index 43a5772..aeb86d6 100644
>>> --- a/fs/ext4/ext4.h
>>> +++ b/fs/ext4/ext4.h
>>> @@ -1729,6 +1729,7 @@ extern int ext4_change_inode_journal_flag(str=
uct inode *, int);
>>> =A0extern int ext4_get_inode_loc(struct inode *, struct ext4_iloc *=
);
>>> =A0extern int ext4_can_truncate(struct inode *inode);
>>> =A0extern void ext4_truncate(struct inode *);
>>> +extern long =A0ext4_punch_hole(struct inode *inode,loff_t offset, =
loff_t length);
>>> =A0extern int ext4_truncate_restart_trans(handle_t *, struct inode =
*, int nblocks);
>>> =A0extern void ext4_set_inode_flags(struct inode *);
>>> =A0extern void ext4_get_inode_flags(struct ext4_inode_info *);
>>> @@ -2066,6 +2067,7 @@ extern int ext4_ext_index_trans_blocks(struct=
 inode *inode, int nrblocks,
>>> =A0extern int ext4_ext_map_blocks(handle_t *handle, struct inode *i=
node,
>>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0struct e=
xt4_map_blocks *map, int flags);
>>> =A0extern void ext4_ext_truncate(struct inode *);
>>> +extern void ext4_ext_punch_hole(struct inode *inode, loff_t offset=
, loff_t length);
>>> =A0extern void ext4_ext_init(struct super_block *);
>>> =A0extern void ext4_ext_release(struct super_block *);
>>> =A0extern long ext4_fallocate(struct file *file, int mode, loff_t o=
ffset,
>>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
>>> index efbc3ef..5713258 100644
>>> --- a/fs/ext4/extents.c
>>> +++ b/fs/ext4/extents.c
>>> @@ -2776,6 +2776,154 @@ out:
>>> =A0}
>>>
>>> =A0/*
>>> + * lookup_hole()
>>> + * Returns the numbers of consecutive blocks starting at "start"
>>> + * that are not contained within an extent
>>> + */
>>
>> The lookup hole path, IMHO, could be a special flag pass to
>> ext4_map_blocks(), reuse existing code, rather adding a new function
>> directly inspecting the inode's allocation tree from there.:)
>>
>>> +static int ext4_ext_lookup_hole(struct inode *inode, ext4_lblk_t s=
tart){
>>> + =A0 =A0struct super_block *sb =3D inode->i_sb;
>>> + =A0 =A0 int depth =3D ext_depth(inode);
>>> + =A0 =A0 struct ext4_ext_path *path;
>>> + =A0 =A0 struct ext4_extent_header *eh;
>>> + =A0 =A0 struct ext4_extent *ex;
>>> + =A0 =A0 struct buffer_head *bh;
>>> + =A0 =A0 ext4_lblk_t last_block;
>>> + =A0 =A0 handle_t *handle;
>>> + =A0 =A0 int i, err;
>>> +
>>> + =A0 =A0 ext_debug("lookup hole since %u\n", start);
>>> +
>>> + =A0 =A0 /* Make sure start is valid */
>>> + =A0 =A0 last_block =3D inode->i_size >> EXT4_BLOCK_SIZE_BITS(sb);
>>> + =A0 =A0 if(start >=3D last_block)
>>> + =A0 =A0 =A0 =A0 =A0 =A0 return -EIO;
>>> +
>>> + =A0 =A0 handle =3D ext4_journal_start(inode, depth + 1);
>>> + =A0 =A0 if (IS_ERR(handle))
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 return PTR_ERR(handle);
>>> +
>>> + =A0 =A0 /*
>>> + =A0 =A0 =A0* We start scanning from right side, looking for
>>> + =A0 =A0 =A0* the left most block contained in the leaf, and
>>> + =A0 =A0 =A0* stopping when "start" is crossed.
>>> + =A0 =A0 =A0*/
>>> + =A0 =A0 depth =3D ext_depth(inode);
>>> + =A0 =A0 path =3D kzalloc(sizeof(struct ext4_ext_path) * (depth + =
1), GFP_NOFS);
>>> + =A0 =A0 if (path =3D=3D NULL) {
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 ext4_journal_stop(handle)=
;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 return -ENOMEM;
>>> + =A0 =A0 }
>>> + =A0 =A0 path[0].p_depth =3D depth;
>>> + =A0 =A0 path[0].p_hdr =3D ext_inode_hdr(inode);
>>> + =A0 =A0 if (ext4_ext_check(inode, path[0].p_hdr, depth)) {
>>> + =A0 =A0 =A0 =A0 =A0 =A0 err =3D -EIO;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 goto out;
>>> + =A0 =A0 }
>>> + =A0 =A0 i =3D err =3D 0;
>>> +
>>> + =A0 =A0 while (i >=3D 0 && err =3D=3D 0) {
>>> + =A0 =A0 =A0 =A0 =A0 =A0 if (i =3D=3D depth) {
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 /* this is leaf block */
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 eh =3D path[i].p_hdr;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 if (eh !=3D NULL){
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 if (eh->e=
h_entries =3D=3D 0){
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 err =3D -EIO;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 goto out;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 }
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 ex =3D EX=
T_LAST_EXTENT(eh);
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 while (ex=
 !=3D NULL && ex >=3D EXT_FIRST_EXTENT(eh)){
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 /*
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0* If the entire extent apears before start
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0* then we have passed the hole.
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0*/
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 if(ex->ee_block + ex->ee_len <=3D start)
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0 =A0 =A0 =A0 goto out;
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 /*
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0* If the start of the extent appears after
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0* or on start, then mark this as the edge
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0* of the hole
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0*/
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 if(ex->ee_block >=3D start)
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0 =A0 =A0 =A0 last_block =3D ex->ee_block;
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 /*
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0* If the extent contains start, then there
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0* is no hole.
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0*/
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 else if(ex->ee_block + ex->ee_len > start){
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0 =A0 =A0 =A0 last_block =3D start;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0 =A0 =A0 =A0 goto out;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 }
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 ex--;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 }
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 }
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 /* root level has p_bh =3D=
=3D NULL, brelse() eats this */
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 brelse(path[i].p_bh);
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 path[i].p_bh =3D NULL;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 i--;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 continue;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 }
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 /* this is index block */
>>> + =A0 =A0 =A0 =A0 =A0 =A0 if (!path[i].p_hdr)
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 path[i].p_hdr =3D ext_blo=
ck_hdr(path[i].p_bh);
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 if (!path[i].p_idx) {
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 /* this level hasn't been=
 touched yet */
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 path[i].p_idx =3D EXT_LAS=
T_INDEX(path[i].p_hdr);
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 path[i].p_block =3D le16_=
to_cpu(path[i].p_hdr->eh_entries)+1;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 ext_debug("init index ptr=
: hdr 0x%p, num %d\n",
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 path[i].p_hdr,
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 le16_to_cpu(path[i].p_hdr=
->eh_entries));
>>> + =A0 =A0 =A0 =A0 =A0 =A0 }
>>> + =A0 =A0 =A0 =A0 =A0 =A0 else {
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 /* we were already here, =
see at next index */
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 path[i].p_idx--;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 }
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 ext_debug("level %d - index, first 0x%p, =
cur 0x%p\n",
>>> + =A0 =A0 =A0 =A0 =A0 =A0 i, EXT_FIRST_INDEX(path[i].p_hdr),
>>> + =A0 =A0 =A0 =A0 =A0 =A0 path[i].p_idx);
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 /* go to the next level */
>>> + =A0 =A0 =A0 =A0 =A0 =A0 ext_debug("move to level %d (block %llu)\=
n",
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 i + 1, ex=
t4_idx_pblock(path[i].p_idx));
>>> + =A0 =A0 =A0 =A0 =A0 =A0 memset(path + i + 1, 0, sizeof(*path));
>>> + =A0 =A0 =A0 =A0 =A0 =A0 bh =3D sb_bread(sb, ext4_idx_pblock(path[=
i].p_idx));
>>> + =A0 =A0 =A0 =A0 =A0 =A0 if (!bh) {
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 err =3D -EIO;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 break;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 }
>>> + =A0 =A0 =A0 =A0 =A0 =A0 if (WARN_ON(i + 1 > depth)) {
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 err =3D -EIO;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 break;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 }
>>> + =A0 =A0 =A0 =A0 =A0 =A0 if (ext4_ext_check(inode, ext_block_hdr(b=
h), depth - i - 1)) {
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 err =3D -EIO;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 break;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 }
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 path[i + 1].p_bh =3D bh;
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 i++;
>>> +
>>> + =A0 =A0 }
>>> +out:
>>> + =A0 =A0 ext4_ext_drop_refs(path);
>>> + =A0 =A0 kfree(path);
>>> + =A0 =A0 ext4_journal_stop(handle);
>>> +
>>> + =A0 =A0 return err ? err : last_block - start;
>>> +
>>> +}
>>> +
>>> +/*
>>> =A0 * called at mount time
>>> =A0 */
>>> =A0void ext4_ext_init(struct super_block *sb)
>>> @@ -4029,6 +4177,172 @@ next:
>>> =A0 =A0 =A0 return ret;
>>> =A0}
>>>
>>> +/*
>>> + * ext4_ext_test_block_flag
>>> + * Tests the buffer head associated with the given block
>>> + * to see if the state contains flag
>>> + *
>>> + * @inode: =A0The inode of the given file
>>> + * @block: =A0The block to test
>>> + * @flag: =A0 The flag to check for
>>> + *
>>> + * Returns 0 on sucess or negative on err
>>> + */
>>> +static int ext4_ext_test_block_flag(struct inode *inode, ext4_lblk=
_t block, enum bh_state_bits flag){
>>> + =A0 =A0 struct buffer_head *bh;
>>> + =A0 =A0 struct page *page;
>>> + =A0 =A0 struct address_space *mapping =3D inode->i_mapping;
>>> + =A0 =A0 loff_t block_offset;
>>> + =A0 =A0 int i, ret;
>>> + =A0 =A0 unsigned long flag_mask =3D 1 << flag;
>>> +
>>> + =A0 =A0 block_offset =3D block << EXT4_BLOCK_SIZE_BITS(inode->i_s=
b);
>>> + =A0 =A0 page =3D find_or_create_page(mapping, block_offset >> PAG=
E_CACHE_SHIFT,
>>> + =A0 =A0 mapping_gfp_mask(mapping) & ~__GFP_FS);
>>> +
>>> + =A0 =A0 if (!page)
>>> + =A0 =A0 =A0 =A0 =A0 =A0 return -EIO;
>>> +
>>> + =A0 =A0 if (!page_has_buffers(page))
>>> + =A0 =A0 =A0 =A0 =A0 =A0 create_empty_buffers(page, EXT4_BLOCK_SIZ=
E(inode->i_sb), 0);
>>> +
>>> + =A0 =A0 /* advance to the buffer that has the block offset =A0*/
>>> + =A0 =A0 bh =3D page_buffers(page);
>>> + =A0 =A0 for (i =3D 0; i < block_offset; i+=3DEXT4_BLOCK_SIZE(inod=
e->i_sb)) {
>>> + =A0 =A0 =A0 =A0 =A0 =A0 bh =3D bh->b_this_page;
>>> + =A0 =A0 }
>>> +
>>> + =A0 =A0 if(bh->b_state & flag_mask)
>>> + =A0 =A0 =A0 =A0 =A0 =A0 ret =3D 0;
>>> + =A0 =A0 else
>>> + =A0 =A0 =A0 =A0 =A0 =A0 ret =3D -1;
>>> +
>>> + =A0 =A0 unlock_page(page);
>>> + =A0 =A0 page_cache_release(page);
>>> +
>>> + =A0 =A0 return ret;
>>> +
>>> +}
>>> +
>>> +/*
>>> + * ext4_ext_punch_hole
>>> + *
>>> + * Punches a hole of "length" bytes in a file starting
>>> + * at byte "offset"
>>> + *
>>> + * @inode: =A0The inode of the file to punch a hole in
>>> + * @offset: The starting byte offset of the hole
>>> + * @length: The length of the hole
>>> + *
>>> + */
>>> +void ext4_ext_punch_hole(struct inode *inode, loff_t offset, loff_=
t length)
>>> +{
>>> + =A0 =A0 struct super_block *sb =3D inode->i_sb;
>>> + =A0 =A0 ext4_lblk_t first_block, last_block, num_blocks, iblock =3D=
 0;
>>> + =A0 =A0 struct address_space *mapping =3D inode->i_mapping;
>>> + =A0 =A0 struct ext4_map_blocks map;
>>> + =A0 =A0 handle_t *handle;
>>> + =A0 =A0 loff_t first_block_offset, last_block_offset, block_len;
>>> + =A0 =A0 int get_blocks_flags, err, ret =3D 0;
>>> +
>>> + =A0 =A0 first_block =3D (offset + sb->s_blocksize - 1)
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 >> EXT4_BLOCK_SIZE_BITS(s=
b);
>>> + =A0 =A0 last_block =3D (offset+length) =A0>> EXT4_BLOCK_SIZE_BITS=
(sb);
>>> +
>>> + =A0 =A0 first_block_offset =3D first_block << EXT4_BLOCK_SIZE_BIT=
S(sb);
>>> + =A0 =A0 last_block_offset =3D last_block << EXT4_BLOCK_SIZE_BITS(=
sb);
>>> +
>>> + =A0 =A0 err =3D ext4_writepage_trans_blocks(inode);
>>> + =A0 =A0 handle =3D ext4_journal_start(inode, err);
>>> + =A0 =A0 if (IS_ERR(handle))
>>> + =A0 =A0 =A0 =A0 =A0 =A0 return;
>>> +
>>> + =A0 =A0 /*
>>> + =A0 =A0 =A0* Now we need to zero out the un block aligned data.
>>> + =A0 =A0 =A0* If the file is smaller than a block, just
>>> + =A0 =A0 =A0* zero out the middle and return
>>> + =A0 =A0 =A0*/
>>> + =A0 =A0 if(first_block > last_block)
>>> + =A0 =A0 =A0 =A0 =A0 =A0 ext4_block_zero_page_range(handle, mappin=
g, offset, length);
>>> + =A0 =A0 else{
>>> + =A0 =A0 =A0 =A0 =A0 =A0 /* zero out the head of the hole before t=
he first block */
>>> + =A0 =A0 =A0 =A0 =A0 =A0 block_len =A0=3D first_block_offset - off=
set;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 if(block_len > 0)
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 ext4_block_zero_page_rang=
e(handle, mapping, offset, block_len);
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 /* zero out the tail of the hole after th=
e last block */
>>> + =A0 =A0 =A0 =A0 =A0 =A0 block_len =3D offset + length - last_bloc=
k_offset;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 if(block_len > 0)
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 ext4_block_zero_page_rang=
e(handle, mapping,
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 last_block_offset, block_len);
>>> + =A0 =A0 }
>>> +
>>> + =A0 =A0 /* If there are no blocks to remove, return now */
>>> + =A0 =A0 if(first_block >=3D last_block){
>>> + =A0 =A0 =A0 =A0 =A0 =A0 ext4_journal_stop(handle);
>>> + =A0 =A0 =A0 =A0 =A0 =A0 return;
>>> + =A0 =A0 }
>>> +
>>> + =A0 =A0 /* Clear pages associated with the hole */
>>> + =A0 =A0 if (mapping->nrpages)
>>> + =A0 =A0 =A0 =A0 =A0 =A0 invalidate_inode_pages2_range(mapping, of=
fset >> PAGE_CACHE_SHIFT,
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
 =A0 =A0 =A0 =A0 =A0 (offset+length) >> PAGE_CACHE_SHIFT );
>>> +
>>> +
>>> + =A0 =A0 /* Loop over all the blocks and identify blocks that need=
 to be punched out */
>>> + =A0 =A0 iblock =3D first_block;
>>> + =A0 =A0 while(iblock < last_block){
>>> + =A0 =A0 =A0 =A0 =A0 =A0 map.m_lblk =3D iblock;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 map.m_len =3D last_block - iblock;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 ret =3D ext4_map_blocks(handle, inode, &m=
ap, 0);
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 /* If the blocks are mapped, release them=
 */
>>> + =A0 =A0 =A0 =A0 =A0 =A0 if(ret > 0){
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 num_blocks =3D ret;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 ext4_ext_convert_blocks_u=
ninit(inode, handle, iblock, num_blocks);
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 ext4_ext_release_blocks(i=
node, iblock, iblock+num_blocks);
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 goto next;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 }
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 /*
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0* If they are not mapped
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0* check to see if they are punched out
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0*/
>>> + =A0 =A0 =A0 =A0 =A0 =A0 ret =3D ext4_ext_lookup_hole(inode, ibloc=
k);
>>> + =A0 =A0 =A0 =A0 =A0 =A0 if(ret > 0){
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 num_blocks =3D ret;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 goto next;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 }
>>> +
>>
>> I am wondering how ext4 FIEMAP handles hole lookup more efficently?
> In ext4 FIEMAP, ext4_ext_walk_space() lookup requested block in exten=
t
> tree firstly, and look next =A0allocated block in extent-tree secondl=
y,
> so if the block is not contained in the found extent, then lookup
> dirty pages starting from offset of the block in pagecahe. =A0Next, f=
ind
> 1st mapped block in the found pages, if the 1st mapped block is not
> delayed and its block nr is less than or equal to the next allocated
> block, then a hole is found.
>
> To lookup a hole, just do as follows.
> 1. lookup block in the extent tree. if the found extent contains the
> request block, then no hole. otherwise, goto 2.
> 2. lookup the next allocated block.
> 3. lookup dirty pages in pagecache starting from offset of the block,
> then find the 1st mapped block. there are 3 cases.
> =A0 a. block number of 1st mapped block is greater than or equal to t=
he
> next allocated block, then a hole is found.
> =A0 b. block number of 1st mapped block is less than the next allocat=
ed block,
> =A0check delayed flag, a delayed extent is found.
     c. should be contained in b case. block number of 1st mapped
block is less than the next allocated block,  and greater than the
request block. A hole is found.

>
>>
>>> + =A0 =A0 =A0 =A0 =A0 =A0 /*
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0* If the block could not be mapped, an=
d
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0* its not already punched out,
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0* check to see if the block is delayed
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0*/
>>> + =A0 =A0 =A0 =A0 =A0 =A0 if(ext4_ext_test_block_flag(inode, iblock=
, BH_Delay) =3D=3D 0){
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 get_blocks_flags =3D EXT4=
_GET_BLOCKS_CREATE | EXT4_GET_BLOCKS_DELALLOC_RESERVE;
>>
>> Ah... the flags, could you check it again? We might get this wrong.
>>
>> EXT4_GET_BLOCKS_CREATE | EXT4_GET_BLOCKS_DELALLOC_RESERVE?
>>
>> these combination means we are plan to do block allocation via delay=
ed
>> allocation path. From inode.c. this flag is aim to tell block alloca=
tion
>> to takes care of block reservation/release for delayed allocation pa=
tch.
>>
>>
>> we should at least turn off the create flag, and check if
>> EXT4_GET_BLOCKS_DELALLOC_RESERVE is also used for delayed extents lo=
ok
>> up also? Maybe I missed something.
>>
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 ret =3D ext4_map_blocks(h=
andle, inode, &map, get_blocks_flags);
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 /* If the blocks are foun=
d, release them */
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 if(ret > 0){
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 num_block=
s =3D ret;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 ext4_ext_=
release_blocks(inode, iblock, iblock+num_blocks);
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 goto next=
;
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 }
>>
>> ext4_ext_release_blocks() is freeing up real storage on disk. For
>> delayed allocation case, there are no blocks allocated yet. We shoul=
d
>> call ext4_da_release_space() or similar to free up the blocks reserv=
ed
>> by delayed allocation.
>>
>>> + =A0 =A0 =A0 =A0 =A0 =A0 }
>>> +
>>> + =A0 =A0 =A0 =A0 =A0 =A0 /* If the block cannot be identified, jus=
t skip it */
>>> + =A0 =A0 =A0 =A0 =A0 =A0 num_blocks =3D 1;
>>> +
>>> +next:
>>> + =A0 =A0 =A0 =A0 =A0 =A0 iblock+=3Dnum_blocks;
>>> + =A0 =A0 }
>>> + =A0 =A0 ext4_mark_inode_dirty(handle, inode);
>>> +
>>> + =A0 =A0 ext4_journal_stop(handle);
>>> +
>>> +}
>>> +
>>>
>>> =A0static void ext4_falloc_update_inode(struct inode *inode,
>>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 int mod=
e, loff_t new_size, int update_ctime)
>>> @@ -4079,10 +4393,6 @@ long ext4_fallocate(struct file *file, int m=
ode, loff_t offset, loff_t len)
>>> =A0 =A0 =A0 struct ext4_map_blocks map;
>>> =A0 =A0 =A0 unsigned int credits, blkbits =3D inode->i_blkbits;
>>>
>>> - =A0 =A0 /* We only support the FALLOC_FL_KEEP_SIZE mode */
>>> - =A0 =A0 if (mode & ~FALLOC_FL_KEEP_SIZE)
>>> - =A0 =A0 =A0 =A0 =A0 =A0 return -EOPNOTSUPP;
>>> -
>>> =A0 =A0 =A0 /*
>>> =A0 =A0 =A0 =A0* currently supporting (pre)allocate mode for extent=
-based
>>> =A0 =A0 =A0 =A0* files _only_
>>> @@ -4090,6 +4400,9 @@ long ext4_fallocate(struct file *file, int mo=
de, loff_t offset, loff_t len)
>>> =A0 =A0 =A0 if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
>>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 return -EOPNOTSUPP;
>>>
>>> + =A0 =A0 if (mode & FALLOC_FL_PUNCH_HOLE)
>>> + =A0 =A0 =A0 =A0 =A0 =A0 return ext4_punch_hole(inode, offset, len=
);
>>> +
>>
>> so for other than the three existing mode, we should also return
>> EOPNOTSUPP too, isn't?
>>
>>> =A0 =A0 =A0 map.m_lblk =3D offset >> blkbits;
>>> =A0 =A0 =A0 /*
>>> =A0 =A0 =A0 =A0* We can't just convert len to max_blocks because
>>> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
>>> index 28c9137..493c908 100644
>>> --- a/fs/ext4/inode.c
>>> +++ b/fs/ext4/inode.c
>>> @@ -4487,6 +4487,32 @@ int ext4_can_truncate(struct inode *inode)
>>> =A0}
>>>
>>> =A0/*
>>> + * ext4_punch_hole: punches a hole in a file by releaseing the blo=
cks
>>> + * associated with the given offset and length
>>> + *
>>> + * @inode: =A0File inode
>>> + * @offset: The offset where the hole will begin
>>> + * @len: =A0 =A0The length of the hole
>>> + *
>>> + * Returns: 0 on sucess or negative on failure
>>> + */
>>> +
>>> +long =A0ext4_punch_hole(struct inode *inode, loff_t offset, loff_t=
 length)
>>> +{
>>> +
>>> + =A0 =A0 if (!S_ISREG(inode->i_mode)=3D=3D1)
>>> + =A0 =A0 =A0 =A0 =A0 =A0 =A0return -ENOTSUPP;
>>> +
>>> + =A0 =A0 if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
>>> + =A0 =A0 =A0 =A0 =A0 =A0 //TODO: Add support for non extent hole p=
unching
>>> + =A0 =A0 =A0 =A0 =A0 =A0 return -ENOTSUPP;
>>> + =A0 =A0 }
>>> +
>>> + =A0 =A0 ext4_ext_punch_hole(inode, offset, length);
>>> + =A0 =A0 return 0;
>>> +}
>>> +
>>> +/*
>>> =A0 * ext4_truncate()
>>> =A0 *
>>> =A0 * We block out ext4_get_block() block instantiations across the=
 entire
>>
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-ext4=
" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at =A0http://vger.kernel.org/majordomo-info.html
>>
>
>
>
> --
> Best Wishes
> Yongqiang Yang
>



--=20
Best Wishes
Yongqiang Yang
--
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