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Date: Mon, 25 Apr 2011 20:44:17 +0300
From: Amir Goldstein <amir73il@...il.com>
To: Yongqiang Yang <xiaoqiangnk@...il.com>
Cc: Allison Henderson <achender@...ux.vnet.ibm.com>,
linux-ext4@...r.kernel.org, Mingming Cao <cmm@...ibm.com>,
Theodore Tso <tytso@....edu>
Subject: Re: [Ext4 punch hole 1/6 v5] Ext4 Punch Hole Support: Add flag to ext4_has_free_blocks
On Mon, Apr 25, 2011 at 12:08 PM, Yongqiang Yang <xiaoqiangnk@...il.com> wrote:
> On Mon, Apr 25, 2011 at 3:51 PM, Amir Goldstein <amir73il@...il.com> wrote:
>> Hi Allison,
>>
>> Sorry for the late response.
>> I find it hard to digest yet another set of flags,
>> especially, since there is already an impressive set of
>> flags for allocation hints, which is what USE_ROOTBLKS flag really is.
>>
>> So I think it would be much better to pass the flag in ext4_allocation_request
>> and add the 'ar' argument to functions that don't have it, rather than adding
>> a 'flags' argument.
> It depends. I had a look at Allison's patch and found that functions
> influenced by the patch can be divided into two groups:
> 1. one of which is extent related and led by ext4_ext_insert_extent()
> 2. while other one of which is very low level such as
> ext4_claim_free_blocks() which is used by ext4_da_reserve_space() in a
> relatively hight level.
>
> So I think maybe it's a good idea for extent related functions, but
> not for low level functions such as ext4_claim_free_blocks.
>
> Actually ext4_ext_insert_extent() seldom allocates blocks, because a
> block can contain a lot of extents. Thus adding 'ar' parameter to
> ext4_ext_insert_extent() induces much unnecessary 'ar''s initializing.
>
Yeah, it's not clear what's the best way to handle this.
>From a system designer point of view, I would suggest to add a capability flag
for allocating from reserved space, but it is probably not going to be
an easy fix to push.
>
>>
>> If you do create a patch to pass 'ar' down to has_free_blocks()
>> I will also be able to use it to pass the HINT_COWING flag.
> HINT_COWING is being passed via 'ar'.
>
indeed, which is why if has_free_blocks gets 'ar' we will have that
flag, which we do not need anyway, since we have the IS_COWING(handle) flag.
> Yongqiang.
>>
>> Now here is another advise:
>> In ext4_mb_new_blocks() after ext4_claim_free_blocks(), there is a call to
>> dquot_alloc_block().
>> You need to call dquot_alloc_block_nofail() when allocating for punch hole,
>> otherwise punch hole can fail on quota limits.
>> We already have a patch for doing that with HINT_COWING flag.
>>
>> I think maybe it is best if our groups (punch hole and snapshots) have
>> a mutual 'next'
>> repository we can work with to prepare for the 2.6.40 merge window.
>> It would be even better, if Ted also collaborated his big alloc patches.
>>
>> What do you think guys?
>>
>> Amir.
>>
>> On Tue, Apr 19, 2011 at 10:41 AM, Allison Henderson
>> <achender@...ux.vnet.ibm.com> wrote:
>>> This patch adds a flag to ext4_has_free_blocks which
>>> enables the use of reserved blocks. This will allow
>>> a punch hole to proceed even if the disk is full.
>>> Punching a hole may require additional blocks to first
>>> split the extents. The blocks will be reclaimed after
>>> the punch hole completes.
>>>
>>> Because ext4_has_free_blocks is a low level function,
>>> the flag needs to be passed down through several
>>> functions listed below:
>>>
>>> ext4_ext_insert_extent
>>> ext4_ext_create_new_leaf
>>> ext4_ext_grow_indepth
>>> ext4_ext_split
>>> ext4_ext_new_meta_block
>>> ext4_mb_new_blocks
>>> ext4_claim_free_blocks
>>> ext4_has_free_blocks
>>>
>>> Signed-off-by: Allison Henderson <achender@...ibm.com>
>>> ---
>>> :100644 100644 97b970e... 794c4d2... M fs/ext4/balloc.c
>>> :100644 100644 4daaf2b... 6c1f415... M fs/ext4/ext4.h
>>> :100644 100644 dd2cb50... 0b186d9... M fs/ext4/extents.c
>>> :100644 100644 1a86282... ec890fd... M fs/ext4/inode.c
>>> :100644 100644 a5837a8... db8b120... M fs/ext4/mballoc.c
>>> :100644 100644 b545ca1... 2d9b12c... M fs/ext4/xattr.c
>>> fs/ext4/balloc.c | 17 ++++++++++-------
>>> fs/ext4/ext4.h | 16 +++++++++++++---
>>> fs/ext4/extents.c | 27 ++++++++++++++++-----------
>>> fs/ext4/inode.c | 6 +++---
>>> fs/ext4/mballoc.c | 5 +++--
>>> fs/ext4/xattr.c | 2 +-
>>> 6 files changed, 46 insertions(+), 27 deletions(-)
>>>
>>> diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
>>> index 97b970e..794c4d2 100644
>>> --- a/fs/ext4/balloc.c
>>> +++ b/fs/ext4/balloc.c
>>> @@ -493,7 +493,8 @@ error_return:
>>> * Check if filesystem has nblocks free & available for allocation.
>>> * On success return 1, return 0 on failure.
>>> */
>>> -static int ext4_has_free_blocks(struct ext4_sb_info *sbi, s64 nblocks)
>>> +static int ext4_has_free_blocks(struct ext4_sb_info *sbi,
>>> + s64 nblocks, int flags)
>>> {
>>> s64 free_blocks, dirty_blocks, root_blocks;
>>> struct percpu_counter *fbc = &sbi->s_freeblocks_counter;
>>> @@ -522,7 +523,9 @@ static int ext4_has_free_blocks(struct ext4_sb_info *sbi, s64 nblocks)
>>> /* Hm, nope. Are (enough) root reserved blocks available? */
>>> if (sbi->s_resuid == current_fsuid() ||
>>> ((sbi->s_resgid != 0) && in_group_p(sbi->s_resgid)) ||
>>> - capable(CAP_SYS_RESOURCE)) {
>>> + capable(CAP_SYS_RESOURCE) ||
>>> + (flags & EXT4_HAS_FREE_BLKS_USE_ROOTBLKS)) {
>>> +
>>> if (free_blocks >= (nblocks + dirty_blocks))
>>> return 1;
>>> }
>>> @@ -531,9 +534,9 @@ static int ext4_has_free_blocks(struct ext4_sb_info *sbi, s64 nblocks)
>>> }
>>>
>>> int ext4_claim_free_blocks(struct ext4_sb_info *sbi,
>>> - s64 nblocks)
>>> + s64 nblocks, int flags)
>>> {
>>> - if (ext4_has_free_blocks(sbi, nblocks)) {
>>> + if (ext4_has_free_blocks(sbi, nblocks, flags)) {
>>> percpu_counter_add(&sbi->s_dirtyblocks_counter, nblocks);
>>> return 0;
>>> } else
>>> @@ -554,7 +557,7 @@ int ext4_claim_free_blocks(struct ext4_sb_info *sbi,
>>> */
>>> int ext4_should_retry_alloc(struct super_block *sb, int *retries)
>>> {
>>> - if (!ext4_has_free_blocks(EXT4_SB(sb), 1) ||
>>> + if (!ext4_has_free_blocks(EXT4_SB(sb), 1, 0) ||
>>> (*retries)++ > 3 ||
>>> !EXT4_SB(sb)->s_journal)
>>> return 0;
>>> @@ -577,7 +580,7 @@ int ext4_should_retry_alloc(struct super_block *sb, int *retries)
>>> * error stores in errp pointer
>>> */
>>> ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
>>> - ext4_fsblk_t goal, unsigned long *count, int *errp)
>>> + ext4_fsblk_t goal, unsigned long *count, int *errp, int flags)
>>> {
>>> struct ext4_allocation_request ar;
>>> ext4_fsblk_t ret;
>>> @@ -588,7 +591,7 @@ ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
>>> ar.goal = goal;
>>> ar.len = count ? *count : 1;
>>>
>>> - ret = ext4_mb_new_blocks(handle, &ar, errp);
>>> + ret = ext4_mb_new_blocks(handle, &ar, errp, flags);
>>> if (count)
>>> *count = ar.len;
>>> /*
>>> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
>>> index 4daaf2b..6c1f415 100644
>>> --- a/fs/ext4/ext4.h
>>> +++ b/fs/ext4/ext4.h
>>> @@ -512,6 +512,8 @@ struct ext4_new_group_data {
>>> /* Convert extent to initialized after IO complete */
>>> #define EXT4_GET_BLOCKS_IO_CONVERT_EXT (EXT4_GET_BLOCKS_CONVERT|\
>>> EXT4_GET_BLOCKS_CREATE_UNINIT_EXT)
>>> + /* Punch out blocks of an extent */
>>> +#define EXT4_GET_BLOCKS_PUNCH_OUT_EXT 0x0020
>>>
>>> /*
>>> * Flags used by ext4_free_blocks
>>> @@ -521,6 +523,11 @@ struct ext4_new_group_data {
>>> #define EXT4_FREE_BLOCKS_VALIDATED 0x0004
>>>
>>> /*
>>> + * Flags used by ext4_has_free_blocks
>>> + */
>>> +#define EXT4_HAS_FREE_BLKS_USE_ROOTBLKS 0x0001
>>> +
>>> +/*
>>> * ioctl commands
>>> */
>>> #define EXT4_IOC_GETFLAGS FS_IOC_GETFLAGS
>>> @@ -1638,8 +1645,10 @@ extern int ext4_bg_has_super(struct super_block *sb, ext4_group_t group);
>>> extern unsigned long ext4_bg_num_gdb(struct super_block *sb,
>>> ext4_group_t group);
>>> extern ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
>>> - ext4_fsblk_t goal, unsigned long *count, int *errp);
>>> -extern int ext4_claim_free_blocks(struct ext4_sb_info *sbi, s64 nblocks);
>>> + ext4_fsblk_t goal, unsigned long *count,
>>> + int *errp, int flags);
>>> +extern int ext4_claim_free_blocks(struct ext4_sb_info *sbi,
>>> + s64 nblocks, int flags);
>>> extern void ext4_add_groupblocks(handle_t *handle, struct super_block *sb,
>>> ext4_fsblk_t block, unsigned long count);
>>> extern ext4_fsblk_t ext4_count_free_blocks(struct super_block *);
>>> @@ -1696,7 +1705,8 @@ extern long ext4_mb_max_to_scan;
>>> extern int ext4_mb_init(struct super_block *, int);
>>> extern int ext4_mb_release(struct super_block *);
>>> extern ext4_fsblk_t ext4_mb_new_blocks(handle_t *,
>>> - struct ext4_allocation_request *, int *);
>>> + struct ext4_allocation_request *,
>>> + int *, int flags);
>>> extern int ext4_mb_reserve_blocks(struct super_block *, int);
>>> extern void ext4_discard_preallocations(struct inode *);
>>> extern int __init ext4_init_mballoc(void);
>>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
>>> index dd2cb50..0b186d9 100644
>>> --- a/fs/ext4/extents.c
>>> +++ b/fs/ext4/extents.c
>>> @@ -192,12 +192,12 @@ static ext4_fsblk_t ext4_ext_find_goal(struct inode *inode,
>>> static ext4_fsblk_t
>>> ext4_ext_new_meta_block(handle_t *handle, struct inode *inode,
>>> struct ext4_ext_path *path,
>>> - struct ext4_extent *ex, int *err)
>>> + struct ext4_extent *ex, int *err, int flags)
>>> {
>>> ext4_fsblk_t goal, newblock;
>>>
>>> goal = ext4_ext_find_goal(inode, path, le32_to_cpu(ex->ee_block));
>>> - newblock = ext4_new_meta_blocks(handle, inode, goal, NULL, err);
>>> + newblock = ext4_new_meta_blocks(handle, inode, goal, NULL, err, flags);
>>> return newblock;
>>> }
>>>
>>> @@ -793,7 +793,7 @@ static int ext4_ext_insert_index(handle_t *handle, struct inode *inode,
>>> */
>>> static int ext4_ext_split(handle_t *handle, struct inode *inode,
>>> struct ext4_ext_path *path,
>>> - struct ext4_extent *newext, int at)
>>> + struct ext4_extent *newext, int at, int flags)
>>> {
>>> struct buffer_head *bh = NULL;
>>> int depth = ext_depth(inode);
>>> @@ -847,7 +847,7 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode,
>>> ext_debug("allocate %d blocks for indexes/leaf\n", depth - at);
>>> for (a = 0; a < depth - at; a++) {
>>> newblock = ext4_ext_new_meta_block(handle, inode, path,
>>> - newext, &err);
>>> + newext, &err, flags);
>>> if (newblock == 0)
>>> goto cleanup;
>>> ablocks[a] = newblock;
>>> @@ -1057,7 +1057,7 @@ cleanup:
>>> */
>>> static int ext4_ext_grow_indepth(handle_t *handle, struct inode *inode,
>>> struct ext4_ext_path *path,
>>> - struct ext4_extent *newext)
>>> + struct ext4_extent *newext, int flags)
>>> {
>>> struct ext4_ext_path *curp = path;
>>> struct ext4_extent_header *neh;
>>> @@ -1065,7 +1065,8 @@ static int ext4_ext_grow_indepth(handle_t *handle, struct inode *inode,
>>> ext4_fsblk_t newblock;
>>> int err = 0;
>>>
>>> - newblock = ext4_ext_new_meta_block(handle, inode, path, newext, &err);
>>> + newblock = ext4_ext_new_meta_block(handle, inode, path,
>>> + newext, &err, flags);
>>> if (newblock == 0)
>>> return err;
>>>
>>> @@ -1141,7 +1142,7 @@ out:
>>> */
>>> static int ext4_ext_create_new_leaf(handle_t *handle, struct inode *inode,
>>> struct ext4_ext_path *path,
>>> - struct ext4_extent *newext)
>>> + struct ext4_extent *newext, int flags)
>>> {
>>> struct ext4_ext_path *curp;
>>> int depth, i, err = 0;
>>> @@ -1161,7 +1162,7 @@ repeat:
>>> if (EXT_HAS_FREE_INDEX(curp)) {
>>> /* if we found index with free entry, then use that
>>> * entry: create all needed subtree and add new leaf */
>>> - err = ext4_ext_split(handle, inode, path, newext, i);
>>> + err = ext4_ext_split(handle, inode, path, newext, i, flags);
>>> if (err)
>>> goto out;
>>>
>>> @@ -1174,7 +1175,7 @@ repeat:
>>> err = PTR_ERR(path);
>>> } else {
>>> /* tree is full, time to grow in depth */
>>> - err = ext4_ext_grow_indepth(handle, inode, path, newext);
>>> + err = ext4_ext_grow_indepth(handle, inode, path, newext, flags);
>>> if (err)
>>> goto out;
>>>
>>> @@ -1668,6 +1669,7 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
>>> int depth, len, err;
>>> ext4_lblk_t next;
>>> unsigned uninitialized = 0;
>>> + int free_blks_flags = 0;
>>>
>>> if (unlikely(ext4_ext_get_actual_len(newext) == 0)) {
>>> EXT4_ERROR_INODE(inode, "ext4_ext_get_actual_len(newext) == 0");
>>> @@ -1742,7 +1744,10 @@ repeat:
>>> * There is no free space in the found leaf.
>>> * We're gonna add a new leaf in the tree.
>>> */
>>> - err = ext4_ext_create_new_leaf(handle, inode, path, newext);
>>> + if (flag & EXT4_GET_BLOCKS_PUNCH_OUT_EXT)
>>> + free_blks_flags = EXT4_HAS_FREE_BLKS_USE_ROOTBLKS;
>>> + err = ext4_ext_create_new_leaf(handle, inode, path,
>>> + newext, free_blks_flags);
>>> if (err)
>>> goto cleanup;
>>> depth = ext_depth(inode);
>>> @@ -3446,7 +3451,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
>>> else
>>> /* disable in-core preallocation for non-regular files */
>>> ar.flags = 0;
>>> - newblock = ext4_mb_new_blocks(handle, &ar, &err);
>>> + newblock = ext4_mb_new_blocks(handle, &ar, &err, 0);
>>> if (!newblock)
>>> goto out2;
>>> ext_debug("allocate new block: goal %llu, found %llu/%u\n",
>>> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
>>> index 1a86282..ec890fd 100644
>>> --- a/fs/ext4/inode.c
>>> +++ b/fs/ext4/inode.c
>>> @@ -640,7 +640,7 @@ static int ext4_alloc_blocks(handle_t *handle, struct inode *inode,
>>> count = target;
>>> /* allocating blocks for indirect blocks and direct blocks */
>>> current_block = ext4_new_meta_blocks(handle, inode,
>>> - goal, &count, err);
>>> + goal, &count, err, 0);
>>> if (*err)
>>> goto failed_out;
>>>
>>> @@ -686,7 +686,7 @@ static int ext4_alloc_blocks(handle_t *handle, struct inode *inode,
>>> /* enable in-core preallocation only for regular files */
>>> ar.flags = EXT4_MB_HINT_DATA;
>>>
>>> - current_block = ext4_mb_new_blocks(handle, &ar, err);
>>> + current_block = ext4_mb_new_blocks(handle, &ar, err, 0);
>>> if (unlikely(current_block + ar.len > EXT4_MAX_BLOCK_FILE_PHYS)) {
>>> EXT4_ERROR_INODE(inode,
>>> "current_block %llu + ar.len %d > %d!",
>>> @@ -1930,7 +1930,7 @@ repeat:
>>> * We do still charge estimated metadata to the sb though;
>>> * we cannot afford to run out of free blocks.
>>> */
>>> - if (ext4_claim_free_blocks(sbi, md_needed + 1)) {
>>> + if (ext4_claim_free_blocks(sbi, md_needed + 1, 0)) {
>>> dquot_release_reservation_block(inode, 1);
>>> if (ext4_should_retry_alloc(inode->i_sb, &retries)) {
>>> yield();
>>> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
>>> index a5837a8..db8b120 100644
>>> --- a/fs/ext4/mballoc.c
>>> +++ b/fs/ext4/mballoc.c
>>> @@ -4276,7 +4276,8 @@ static int ext4_mb_discard_preallocations(struct super_block *sb, int needed)
>>> * to usual allocation
>>> */
>>> ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
>>> - struct ext4_allocation_request *ar, int *errp)
>>> + struct ext4_allocation_request *ar, int *errp,
>>> + int flags)
>>> {
>>> int freed;
>>> struct ext4_allocation_context *ac = NULL;
>>> @@ -4303,7 +4304,7 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
>>> * there is enough free blocks to do block allocation
>>> * and verify allocation doesn't exceed the quota limits.
>>> */
>>> - while (ar->len && ext4_claim_free_blocks(sbi, ar->len)) {
>>> + while (ar->len && ext4_claim_free_blocks(sbi, ar->len, flags)) {
>>> /* let others to free the space */
>>> yield();
>>> ar->len = ar->len >> 1;
>>> diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
>>> index b545ca1..2d9b12c 100644
>>> --- a/fs/ext4/xattr.c
>>> +++ b/fs/ext4/xattr.c
>>> @@ -821,7 +821,7 @@ inserted:
>>> goal = goal & EXT4_MAX_BLOCK_FILE_PHYS;
>>>
>>> block = ext4_new_meta_blocks(handle, inode,
>>> - goal, NULL, &error);
>>> + goal, NULL, &error, 0);
>>> if (error)
>>> goto cleanup;
>>>
>>> --
>>> 1.7.1
>>>
>>> --
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>>>
>>
>
>
>
> --
> Best Wishes
> Yongqiang Yang
>
--
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