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Date: Tue, 01 Mar 2011 13:51:37 -0700
From: Allison Henderson <achender@...ux.vnet.ibm.com>
To: Amir Goldstein <amir73il@...il.com>
CC: Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [Ext4 punch hole 4/5] Ext4 Punch Hole Support: Enable Punch Hole
On 3/1/2011 1:20 AM, Amir Goldstein wrote:
> On Tue, Mar 1, 2011 at 5:09 AM, Allison Henderson
> <achender@...ux.vnet.ibm.com> wrote:
>> This patch adds the new "ext4_punch_hole" "ext4_ext_punch_hole" routines.
>>
>> fallocate has been modified to call ext4_punch_hole when the punch hole
>> flag is passed. At 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. The 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. The blocks are then punched out using the
>> "ext4_ext_release_blocks" routine.
>>
>> 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@...ibm.com>
>> ---
>> :100644 100644 43a5772... aeb86d6... M fs/ext4/ext4.h
>> :100644 100644 efbc3ef... 5713258... M fs/ext4/extents.c
>> :100644 100644 28c9137... 493c908... M fs/ext4/inode.c
>> fs/ext4/ext4.h | 2 +
>> fs/ext4/extents.c | 321 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
>> fs/ext4/inode.c | 26 +++++
>> 3 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(struct inode *, int);
>> extern int ext4_get_inode_loc(struct inode *, struct ext4_iloc *);
>> extern int ext4_can_truncate(struct inode *inode);
>> extern void ext4_truncate(struct inode *);
>> +extern long ext4_punch_hole(struct inode *inode,loff_t offset, loff_t length);
>> extern int ext4_truncate_restart_trans(handle_t *, struct inode *, int nblocks);
>> extern void ext4_set_inode_flags(struct inode *);
>> extern 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,
>> extern int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
>> struct ext4_map_blocks *map, int flags);
>> extern void ext4_ext_truncate(struct inode *);
>> +extern void ext4_ext_punch_hole(struct inode *inode, loff_t offset, loff_t length);
>> extern void ext4_ext_init(struct super_block *);
>> extern void ext4_ext_release(struct super_block *);
>> extern long ext4_fallocate(struct file *file, int mode, loff_t offset,
>> 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:
>> }
>>
>> /*
>> + * lookup_hole()
>> + * Returns the numbers of consecutive blocks starting at "start"
>> + * that are not contained within an extent
>> + */
>> +static int ext4_ext_lookup_hole(struct inode *inode, ext4_lblk_t start){
>> + struct super_block *sb = inode->i_sb;
>> + int depth = ext_depth(inode);
>> + struct ext4_ext_path *path;
>> + struct ext4_extent_header *eh;
>> + struct ext4_extent *ex;
>> + struct buffer_head *bh;
>> + ext4_lblk_t last_block;
>> + handle_t *handle;
>> + int i, err;
>> +
>> + ext_debug("lookup hole since %u\n", start);
>> +
>> + /* Make sure start is valid */
>> + last_block = inode->i_size>> EXT4_BLOCK_SIZE_BITS(sb);
>> + if(start>= last_block)
>> + return -EIO;
>> +
>> + handle = ext4_journal_start(inode, depth + 1);
>> + if (IS_ERR(handle))
>> + return PTR_ERR(handle);
>
> This is strange. The name of the functions implies it is a readonly operation,
> so why is a transaction needed?
> You should probably document the reason for that and specify the changes
> which this function may apply.
Oh, I must have been doing something that required at handle at one point, and forgot to take this out. Thx for catching it, I will pull out the code for the handle.
>
>> +
>> + /*
>> + * We start scanning from right side, looking for
>> + * the left most block contained in the leaf, and
>> + * stopping when "start" is crossed.
>> + */
>> + depth = ext_depth(inode);
>> + path = kzalloc(sizeof(struct ext4_ext_path) * (depth + 1), GFP_NOFS);
>> + if (path == NULL) {
>> + ext4_journal_stop(handle);
>> + return -ENOMEM;
>> + }
>> + path[0].p_depth = depth;
>> + path[0].p_hdr = ext_inode_hdr(inode);
>> + if (ext4_ext_check(inode, path[0].p_hdr, depth)) {
>> + err = -EIO;
>> + goto out;
>> + }
>> + i = err = 0;
>> +
>> + while (i>= 0&& err == 0) {
>> + if (i == depth) {
>> + /* this is leaf block */
>> +
>> + eh = path[i].p_hdr;
>> + if (eh != NULL){
>> + if (eh->eh_entries == 0){
>> + err = -EIO;
>> + goto out;
>> + }
>> +
>> + ex = EXT_LAST_EXTENT(eh);
>> + while (ex != NULL&& ex>= EXT_FIRST_EXTENT(eh)){
>> +
>> + /*
>> + * If the entire extent apears before start
>> + * then we have passed the hole.
>> + */
>> + if(ex->ee_block + ex->ee_len<= start)
>> + goto out;
>> +
>> + /*
>> + * If the start of the extent appears after
>> + * or on start, then mark this as the edge
>> + * of the hole
>> + */
>> + if(ex->ee_block>= start)
>> + last_block = ex->ee_block;
>> +
>> + /*
>> + * If the extent contains start, then there
>> + * is no hole.
>> + */
>> + else if(ex->ee_block + ex->ee_len> start){
>> + last_block = start;
>> + goto out;
>> + }
>> +
>> + ex--;
>> + }
>> + }
>> +
>> + /* root level has p_bh == NULL, brelse() eats this */
>> + brelse(path[i].p_bh);
>> + path[i].p_bh = NULL;
>> + i--;
>> + continue;
>> + }
>> +
>> + /* this is index block */
>> + if (!path[i].p_hdr)
>> + path[i].p_hdr = ext_block_hdr(path[i].p_bh);
>> +
>> + if (!path[i].p_idx) {
>> + /* this level hasn't been touched yet */
>> + path[i].p_idx = EXT_LAST_INDEX(path[i].p_hdr);
>> + path[i].p_block = le16_to_cpu(path[i].p_hdr->eh_entries)+1;
>> + ext_debug("init index ptr: hdr 0x%p, num %d\n",
>> + path[i].p_hdr,
>> + le16_to_cpu(path[i].p_hdr->eh_entries));
>> + }
>> + else {
>> + /* we were already here, see at next index */
>> + path[i].p_idx--;
>> + }
>> +
>> + ext_debug("level %d - index, first 0x%p, cur 0x%p\n",
>> + i, EXT_FIRST_INDEX(path[i].p_hdr),
>> + path[i].p_idx);
>> +
>> + /* go to the next level */
>> + ext_debug("move to level %d (block %llu)\n",
>> + i + 1, ext4_idx_pblock(path[i].p_idx));
>> + memset(path + i + 1, 0, sizeof(*path));
>> + bh = sb_bread(sb, ext4_idx_pblock(path[i].p_idx));
>> + if (!bh) {
>> + err = -EIO;
>> + break;
>> + }
>> + if (WARN_ON(i + 1> depth)) {
>> + err = -EIO;
>> + break;
>> + }
>> + if (ext4_ext_check(inode, ext_block_hdr(bh), depth - i - 1)) {
>> + err = -EIO;
>> + break;
>> + }
>> +
>> + path[i + 1].p_bh = bh;
>> +
>> + i++;
>> +
>> + }
>> +out:
>> + ext4_ext_drop_refs(path);
>> + kfree(path);
>> + ext4_journal_stop(handle);
>> +
>> + return err ? err : last_block - start;
>> +
>> +}
>> +
>> +/*
>> * called at mount time
>> */
>> void ext4_ext_init(struct super_block *sb)
>> @@ -4029,6 +4177,172 @@ next:
>> return ret;
>> }
>>
>> +/*
>> + * ext4_ext_test_block_flag
>> + * Tests the buffer head associated with the given block
>> + * to see if the state contains flag
>> + *
>> + * @inode: The inode of the given file
>> + * @block: The block to test
>> + * @flag: 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){
>
> (style) open { in new line.
>
>> + struct buffer_head *bh;
>> + struct page *page;
>> + struct address_space *mapping = inode->i_mapping;
>> + loff_t block_offset;
>> + int i, ret;
>> + unsigned long flag_mask = 1<< flag;
>> +
>> + block_offset = block<< EXT4_BLOCK_SIZE_BITS(inode->i_sb);
>> + page = find_or_create_page(mapping, block_offset>> PAGE_CACHE_SHIFT,
>> + mapping_gfp_mask(mapping)& ~__GFP_FS);
>> +
>> + if (!page)
>> + return -EIO;
>> +
>> + if (!page_has_buffers(page))
>> + create_empty_buffers(page, EXT4_BLOCK_SIZE(inode->i_sb), 0);
>> +
>> + /* advance to the buffer that has the block offset */
>> + bh = page_buffers(page);
>> + for (i = 0; i< block_offset; i+=EXT4_BLOCK_SIZE(inode->i_sb)) {
>> + bh = bh->b_this_page;
>> + }
>> +
>> + if(bh->b_state& flag_mask)
>> + ret = 0;
>> + else
>> + ret = -1;
>> +
>> + unlock_page(page);
>> + page_cache_release(page);
>> +
>> + return ret;
>> +
>> +}
>> +
>> +/*
>> + * ext4_ext_punch_hole
>> + *
>> + * Punches a hole of "length" bytes in a file starting
>> + * at byte "offset"
>> + *
>> + * @inode: The 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)
>> +{
>> + struct super_block *sb = inode->i_sb;
>> + ext4_lblk_t first_block, last_block, num_blocks, iblock = 0;
>> + struct address_space *mapping = inode->i_mapping;
>> + struct ext4_map_blocks map;
>> + handle_t *handle;
>> + loff_t first_block_offset, last_block_offset, block_len;
>> + int get_blocks_flags, err, ret = 0;
>> +
>> + first_block = (offset + sb->s_blocksize - 1)
>> +>> EXT4_BLOCK_SIZE_BITS(sb);
>> + last_block = (offset+length)>> EXT4_BLOCK_SIZE_BITS(sb);
>> +
>> + first_block_offset = first_block<< EXT4_BLOCK_SIZE_BITS(sb);
>> + last_block_offset = last_block<< EXT4_BLOCK_SIZE_BITS(sb);
>> +
>> + err = ext4_writepage_trans_blocks(inode);
>
> 1. (style) err is not an appropriate name (even though is it
> convenient to reuse it)
> 2. did you check if ext4_writepage_trans_blocks(inode) covers the credits
> needed for splitting 1 extent into 3? I suppose it does if it also
> being used
> when converting a middle part of an uninitialized extent, but I
> didn't check.
>
>> + handle = ext4_journal_start(inode, err);
>> + if (IS_ERR(handle))
>> + return;
>> +
>> + /*
>> + * Now we need to zero out the un block aligned data.
>> + * If the file is smaller than a block, just
>> + * zero out the middle and return
>> + */
>> + if(first_block> last_block)
>> + ext4_block_zero_page_range(handle, mapping, offset, length);
>> + else{
>> + /* zero out the head of the hole before the first block */
>> + block_len = first_block_offset - offset;
>> + if(block_len> 0)
>> + ext4_block_zero_page_range(handle, mapping, offset, block_len);
>> +
>> + /* zero out the tail of the hole after the last block */
>> + block_len = offset + length - last_block_offset;
>> + if(block_len> 0)
>> + ext4_block_zero_page_range(handle, mapping,
>> + last_block_offset, block_len);
>> + }
>> +
>> + /* If there are no blocks to remove, return now */
>> + if(first_block>= last_block){
>> + ext4_journal_stop(handle);
>> + return;
>> + }
>> +
>> + /* Clear pages associated with the hole */
>> + if (mapping->nrpages)
>> + invalidate_inode_pages2_range(mapping, offset>> PAGE_CACHE_SHIFT,
>> + (offset+length)>> PAGE_CACHE_SHIFT );
>> +
>> +
>> + /* Loop over all the blocks and identify blocks that need to be punched out */
>> + iblock = first_block;
>> + while(iblock< last_block){
>> + map.m_lblk = iblock;
>> + map.m_len = last_block - iblock;
>> + ret = ext4_map_blocks(handle, inode,&map, 0);
>> +
>> + /* If the blocks are mapped, release them */
>> + if(ret> 0){
>> + num_blocks = ret;
>> + ext4_ext_convert_blocks_uninit(inode, handle, iblock, num_blocks);
>> + ext4_ext_release_blocks(inode, iblock, iblock+num_blocks);
>> + goto next;
>> + }
>> +
>> + /*
>> + * If they are not mapped
>> + * check to see if they are punched out
>> + */
>> + ret = ext4_ext_lookup_hole(inode, iblock);
>> + if(ret> 0){
>> + num_blocks = ret;
>> + goto next;
>> + }
>> +
>> + /*
>> + * If the block could not be mapped, and
>> + * its not already punched out,
>> + * check to see if the block is delayed
>> + */
>> + if(ext4_ext_test_block_flag(inode, iblock, BH_Delay) == 0){
>> + get_blocks_flags = EXT4_GET_BLOCKS_CREATE | EXT4_GET_BLOCKS_DELALLOC_RESERVE;
>> + ret = ext4_map_blocks(handle, inode,&map, get_blocks_flags);
>> + /* If the blocks are found, release them */
>> +
>> + if(ret> 0){
>> + num_blocks = ret;
>> + ext4_ext_release_blocks(inode, iblock, iblock+num_blocks);
>> + goto next;
>> + }
>> + }
>> +
>> + /* If the block cannot be identified, just skip it */
>> + num_blocks = 1;
>> +
>> +next:
>> + iblock+=num_blocks;
>> + }
>> + ext4_mark_inode_dirty(handle, inode);
>> +
>> + ext4_journal_stop(handle);
>> +
>> +}
>> +
>>
>> static void ext4_falloc_update_inode(struct inode *inode,
>> int mode, loff_t new_size, int update_ctime)
>> @@ -4079,10 +4393,6 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
>> struct ext4_map_blocks map;
>> unsigned int credits, blkbits = inode->i_blkbits;
>>
>> - /* We only support the FALLOC_FL_KEEP_SIZE mode */
>> - if (mode& ~FALLOC_FL_KEEP_SIZE)
>> - return -EOPNOTSUPP;
>> -
>> /*
>> * currently supporting (pre)allocate mode for extent-based
>> * files _only_
>> @@ -4090,6 +4400,9 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
>> if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
>> return -EOPNOTSUPP;
>>
>> + if (mode& FALLOC_FL_PUNCH_HOLE)
>> + return ext4_punch_hole(inode, offset, len);
>> +
>> map.m_lblk = offset>> blkbits;
>> /*
>> * 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)
>> }
>>
>> /*
>> + * ext4_punch_hole: punches a hole in a file by releaseing the blocks
>> + * associated with the given offset and length
>> + *
>> + * @inode: File inode
>> + * @offset: The offset where the hole will begin
>> + * @len: The length of the hole
>> + *
>> + * Returns: 0 on sucess or negative on failure
>> + */
>> +
>> +long ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length)
>> +{
>> +
>> + if (!S_ISREG(inode->i_mode)==1)
>> + return -ENOTSUPP;
>
> (style) please drop the == 1. I am not even sure that !(0) is
> guarantied to return 1...
>
>> +
>> + if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
>> + //TODO: Add support for non extent hole punching
>> + return -ENOTSUPP;
>> + }
>> +
>> + ext4_ext_punch_hole(inode, offset, length);
>> + return 0;
>> +}
>> +
>> +/*
>> * ext4_truncate()
>> *
>> * We block out ext4_get_block() block instantiations across the entire
>> --
>> 1.7.1
>>
>>
>> --
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>>
Thx for the feedback! I will check into the ext4_writepage_trans_blocks routine to make sure it has enough credits, and I will update the rest of the patch with the style fixes.
Allison Henderson
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