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Message-ID: <5925e2c0-e85f-4e83-a41a-594d954814a1@kernel.org>
Date: Wed, 20 Nov 2024 18:03:52 +0800
From: Chao Yu <chao@...nel.org>
To: Zhiguo Niu <niuzhiguo84@...il.com>
Cc: Chao Yu <chao@...nel.org>, Xiuhong Wang <xiuhong.wang.cn@...il.com>,
Xiuhong Wang <xiuhong.wang@...soc.com>, jaegeuk@...nel.org,
linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
hao_hao.wang@...soc.com, ke.wang@...soc.com
Subject: Re: [PATCH] f2fs: Fix to avoid long time to shrink extent cache
On 2024/11/20 17:19, Zhiguo Niu wrote:
> Chao Yu <chao@...nel.org> 于2024年11月20日周三 16:15写道：
>>
>> On 2024/11/20 13:45, Zhiguo Niu wrote:
>>> Chao Yu <chao@...nel.org> 于2024年11月20日周三 11:26写道：
>>>>
>>>> On 2024/11/19 16:26, Zhiguo Niu wrote:
>>>>> Chao Yu <chao@...nel.org> 于2024年11月19日周二 15:50写道：
>>>>>>
>>>>>> On 2024/11/19 14:46, Xiuhong Wang wrote:
>>>>>>> Chao Yu <chao@...nel.org> 于2024年11月19日周二 14:05写道：
>>>>>>>>
>>>>>>>> On 2024/11/12 19:06, Xiuhong Wang wrote:
>>>>>>>>> We encountered a system hang problem based on the following
>>>>>>>>> experiment:
>>>>>>>>> There are 17 processes, 8 of which do 4k data read, write and
>>>>>>>>> compare tests, and 8 do 64k read, write and compare tests. Each
>>>>>>>>> thread writes a 256M file, and another thread writes a large file
>>>>>>>>> to 80% of the disk, and then keeps doing read operations, all of
>>>>>>>>> which are direct operations. This will cause the large file to be
>>>>>>>>> filled to 80% of the disk to be severely fragmented. On a 512GB
>>>>>>>>> device, this large file may generate a huge zombie extent tree.
>>>>>>>>>
>>>>>>>>> When system shutting down, the init process needs to wait for the
>>>>>>>>> writeback process, and the writeback process may encounter the
>>>>>>>>> situation where the READ_EXTENT_CACHE space is insufficient and
>>>>>>>>> needs to free the zombie extent tree. The extent tree has a large
>>>>>>>>> number of extent nodes, it will a long free time to free, which
>>>>>>>>> triggers system hang.
>>>>>>>> > > The stack when the problem occurs is as follows:
>>>>>>>>> crash_arm64> bt 1
>>>>>>>>> PID: 1 TASK: ffffff80801a9200 CPU: 1 COMMAND: "init"
>>>>>>>>> #0 [ffffffc00806b9a0] __switch_to at ffffffc00810711c
>>>>>>>>> #1 [ffffffc00806ba00] __schedule at ffffffc0097c1c4c
>>>>>>>>> #2 [ffffffc00806ba60] schedule at ffffffc0097c2308
>>>>>>>>> #3 [ffffffc00806bab0] wb_wait_for_completion at ffffffc0086320d4
>>>>>>>>> #4 [ffffffc00806bb20] writeback_inodes_sb at ffffffc00863719c
>>>>>>>>> #5 [ffffffc00806bba0] sync_filesystem at ffffffc00863c98c
>>>>>>>>> #6 [ffffffc00806bbc0] f2fs_quota_off_umount at ffffffc00886fc60
>>>>>>>>> #7 [ffffffc00806bc20] f2fs_put_super at ffffffc0088715b4
>>>>>>>>> #8 [ffffffc00806bc60] generic_shutdown_super at ffffffc0085cd61c
>>>>>>>>> #9 [ffffffc00806bcd0] kill_f2fs_super at ffffffc00886b3dc
>>>>>>>>>
>>>>>>>>> crash_arm64> bt 14997
>>>>>>>>> PID: 14997 TASK: ffffff8119d82400 CPU: 3 COMMAND: "kworker/u16:0"
>>>>>>>>> #0 [ffffffc019f8b760] __detach_extent_node at ffffffc0088d5a58
>>>>>>>>> #1 [ffffffc019f8b790] __release_extent_node at ffffffc0088d5970
>>>>>>>>> #2 [ffffffc019f8b810] f2fs_shrink_extent_tree at ffffffc0088d5c7c
>>>>>>>>> #3 [ffffffc019f8b8a0] f2fs_balance_fs_bg at ffffffc0088c109c
>>>>>>>>> #4 [ffffffc019f8b910] f2fs_write_node_pages at ffffffc0088bd4d8
>>>>>>>>> #5 [ffffffc019f8b990] do_writepages at ffffffc0084a0b5c
>>>>>>>>> #6 [ffffffc019f8b9f0] __writeback_single_inode at ffffffc00862ee28
>>>>>>>>> #7 [ffffffc019f8bb30] writeback_sb_inodes at ffffffc0086358c0
>>>>>>>>> #8 [ffffffc019f8bc10] wb_writeback at ffffffc0086362dc
>>>>>>>>> #9 [ffffffc019f8bcc0] wb_do_writeback at ffffffc008634910
>>>>>>>>>
>>>>>>>>> Process 14997 ran for too long and caused the system hang.
>>>>>>>>>
>>>>>>>>> At this time, there are still 1086911 extent nodes in this zombie
>>>>>>>>> extent tree that need to be cleaned up.
>>>>>>>>>
>>>>>>>>> crash_arm64_sprd_v8.0.3++> extent_tree.node_cnt ffffff80896cc500
>>>>>>>>> node_cnt = {
>>>>>>>>> counter = 1086911
>>>>>>>>> },
>>>>>>>>>
>>>>>>>>> The root cause of this problem is that when the f2fs_balance_fs
>>>>>>>>> function is called in the write process, it will determine
>>>>>>>>> whether to call f2fs_balance_fs_bg, but it is difficult to
>>>>>>>>> meet the condition of excess_cached_nats. When the
>>>>>>>>> f2fs_shrink_extent_tree function is called to free during
>>>>>>>>> f2fs_write_node_pages, there are too many extent nodes on the
>>>>>>>>> extent tree, which causes a loop and causes a system hang.
>>>>>>>>>
>>>>>>>>> To solve this problem, when calling f2fs_balance_fs, check whether
>>>>>>>>> the extent cache is sufficient. If not, release the zombie extent
>>>>>>>>> tree.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Xiuhong Wang <xiuhong.wang@...soc.com>
>>>>>>>>> Signed-off-by: Zhiguo Niu <zhiguo.niu@...soc.com>
>>>>>>>>> ---
>>>>>>>>> Test the problem with the temporary versions:
>>>>>>>>> patch did not reproduce the problem, the patch is as follows:
>>>>>>>>> @@ -415,7 +415,7 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need)
>>>>>>>>> f2fs_stop_checkpoint(sbi, false, STOP_CP_REASON_FAULT_INJECT);
>>>>>>>>>
>>>>>>>>> /* balance_fs_bg is able to be pending */
>>>>>>>>> - if (need && excess_cached_nats(sbi))
>>>>>>>>> + if (need)
>>>>>>>>> f2fs_balance_fs_bg(sbi, false);
>>>>>>>>>
>>>>>>>>> ---
>>>>>>>>> fs/f2fs/segment.c | 4 +++-
>>>>>>>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>>>>>>>>
>>>>>>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>>>>>>> index 1766254279d2..390bec177567 100644
>>>>>>>>> --- a/fs/f2fs/segment.c
>>>>>>>>> +++ b/fs/f2fs/segment.c
>>>>>>>>> @@ -415,7 +415,9 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need)
>>>>>>>>> f2fs_stop_checkpoint(sbi, false, STOP_CP_REASON_FAULT_INJECT);
>>>>>>>>>
>>>>>>>>> /* balance_fs_bg is able to be pending */
>>>>>>>>> - if (need && excess_cached_nats(sbi))
>>>>>>>>> + if (need && (excess_cached_nats(sbi) ||
>>>>>>>>> + !f2fs_available_free_memory(sbi, READ_EXTENT_CACHE) ||
>>>>>>>>> + !f2fs_available_free_memory(sbi, AGE_EXTENT_CACHE)))
>>>>>>>>
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> I doubt if there is no enough memory, we may still run into
>>>>>>>> f2fs_shrink_extent_tree() and suffer such long time delay.
>>>>>>>>
>>>>>>>> So, can we just let __free_extent_tree() break the loop once we have
>>>>>>>> released entries w/ target number? something like this:
>>>>>>>>
>>>>>>>> ---
>>>>>>>> fs/f2fs/extent_cache.c | 15 ++++++++++-----
>>>>>>>> 1 file changed, 10 insertions(+), 5 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
>>>>>>>> index 019c1f7b7fa5..38c71c1c4fb7 100644
>>>>>>>> --- a/fs/f2fs/extent_cache.c
>>>>>>>> +++ b/fs/f2fs/extent_cache.c
>>>>>>>> @@ -379,11 +379,12 @@ static struct extent_tree *__grab_extent_tree(struct inode *inode,
>>>>>>>> }
>>>>>>>>
>>>>>>>> static unsigned int __free_extent_tree(struct f2fs_sb_info *sbi,
>>>>>>>> - struct extent_tree *et)
>>>>>>>> + struct extent_tree *et, unsigned int nr_shrink)
>>>>>>>> {
>>>>>>>> struct rb_node *node, *next;
>>>>>>>> struct extent_node *en;
>>>>>>>> unsigned int count = atomic_read(&et->node_cnt);
>>>>>>>> + unsigned int i = 0;
>>>>>>>>
>>>>>>>> node = rb_first_cached(&et->root);
>>>>>>>> while (node) {
>>>>>>>> @@ -391,6 +392,9 @@ static unsigned int __free_extent_tree(struct f2fs_sb_info *sbi,
>>>>>>>> en = rb_entry(node, struct extent_node, rb_node);
>>>>>>>> __release_extent_node(sbi, et, en);
>>>>>>>> node = next;
>>>>>>>> +
>>>>>>>> + if (nr_shrink && ++i >= nr_shrink)
>>>>>>>> + break;
>>>>>>>> }
>>>>>>>>
>>>>>>>> return count - atomic_read(&et->node_cnt);
>>>>>>>> @@ -761,7 +765,7 @@ static void __update_extent_tree_range(struct inode *inode,
>>>>>>>> }
>>>>>>>>
>>>>>>>> if (is_inode_flag_set(inode, FI_NO_EXTENT))
>>>>>>>> - __free_extent_tree(sbi, et);
>>>>>>>> + __free_extent_tree(sbi, et, 0);
>>>>>>>>
>>>>>>>> if (et->largest_updated) {
>>>>>>>> et->largest_updated = false;
>>>>>>>> @@ -942,7 +946,8 @@ static unsigned int __shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink
>>>>>>>> list_for_each_entry_safe(et, next, &eti->zombie_list, list) {
>>>>>>>> if (atomic_read(&et->node_cnt)) {
>>>>>>>> write_lock(&et->lock);
>>>>>>>> - node_cnt += __free_extent_tree(sbi, et);
>>>>>>>> + node_cnt += __free_extent_tree(sbi, et,
>>>>>>>> + nr_shrink - node_cnt - tree_cnt);
>>>>>>>> write_unlock(&et->lock);
>>>>>>>> }
>>>>>>>> f2fs_bug_on(sbi, atomic_read(&et->node_cnt));
>>>>>>>> @@ -1095,7 +1100,7 @@ static unsigned int __destroy_extent_node(struct inode *inode,
>>>>>>>> return 0;
>>>>>>>>
>>>>>>>> write_lock(&et->lock);
>>>>>>>> - node_cnt = __free_extent_tree(sbi, et);
>>>>>>>> + node_cnt = __free_extent_tree(sbi, et, 0);
>>>>>>>> write_unlock(&et->lock);
>>>>>>>>
>>>>>>>> return node_cnt;
>>>>>>>> @@ -1117,7 +1122,7 @@ static void __drop_extent_tree(struct inode *inode, enum extent_type type)
>>>>>>>> return;
>>>>>>>>
>>>>>>>> write_lock(&et->lock);
>>>>>>>> - __free_extent_tree(sbi, et);
>>>>>>>> + __free_extent_tree(sbi, et, 0);
>>>>>>>> if (type == EX_READ) {
>>>>>>>> set_inode_flag(inode, FI_NO_EXTENT);
>>>>>>>> if (et->largest.len) {
>>>>>>>> --
>>>>>>>> 2.40.1
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>>> f2fs_balance_fs_bg(sbi, false);
>>>>>>>>>
>>>>>>>>> if (!f2fs_is_checkpoint_ready(sbi))
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Hi chao,
>>>>>>>
>>>>>>> We have also considered this approach, but the problem still occurs
>>>>>>> after retesting.
>>>>>>> 1. The problem still occurs in the following call of the unmount data process.
>>>>>>> f2fs_put_super -> f2fs_leave_shrinker
>>>>>>
>>>>>> Yes, I guess we need to fix this path as well, however, your patch didn't
>>>>>> cover this path as well, am I missing something?
>>>>> Dear Chao,
>>>>> This patch version aim to shrink extent cache as early as possible on
>>>>> the "all write path"
>>>>> by "write action" -> f2fs_balance_fs -> f2fs_balance_fs_bg
>>>>
>>>> Zhiguo, thanks for explaining again.
>>>>
>>> Dear Chao,
>>>> However, I doubt covering all write paths is not enough, because extent
>>>> node can increase when f2fs_precache_extents() was called from paths
>>>> including fadvise/fiemap/swapon/ioc_precache_extents, and there may be
>>>> no writeback, so we may get no chance to call into f2fs_balance_fs_bg(),
>>>> e.g. there is no data update in mountpoint, or mountpoint is readonly.
>>> yes, Indeed it is.
>>>>
>>>>> As the comment , the "excess_cached_nats" is difficult to achieve in
>>>>> this scenario, and
>>>>
>>>> Another concern is, in high-end products w/ more memory, it may has less
>>>> chance to hit newly added condition in f2fs_balance_fs()? not sure though.
>>> I also agree with this.
>>> There is no other better idea for me(^^) excpetion for the two methods
>>> we discussed above.
>>> any good suggestions ? ^^
>>
> Dear Chao,
> It is good solution to limit the maximum extent count of each inode.
>> What do you think of this?
>>
>> From 8646c28027d5b050938335066ab56abbeca799e7 Mon Sep 17 00:00:00 2001
>> From: Chao Yu <chao@...nel.org>
>> Date: Tue, 19 Nov 2024 11:53:09 +0800
>> Subject: [PATCH 1/2] f2fs: fix to shrink read extent node in batches
>>
>> Signed-off-by: Chao Yu <chao@...nel.org>
>> ---
>> fs/f2fs/extent_cache.c | 64 ++++++++++++++++++++++++------------------
>> 1 file changed, 37 insertions(+), 27 deletions(-)
>>
>> diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
>> index 019c1f7b7fa5..0c0d05f8551a 100644
>> --- a/fs/f2fs/extent_cache.c
>> +++ b/fs/f2fs/extent_cache.c
>> @@ -379,21 +379,22 @@ static struct extent_tree *__grab_extent_tree(struct inode *inode,
>> }
>>
>> static unsigned int __free_extent_tree(struct f2fs_sb_info *sbi,
>> - struct extent_tree *et)
>> + struct extent_tree *et, unsigned int nr_shrink)
>> {
>> struct rb_node *node, *next;
>> struct extent_node *en;
>> - unsigned int count = atomic_read(&et->node_cnt);
>> + unsigned int count;
>>
>> node = rb_first_cached(&et->root);
>> - while (node) {
>> +
>> + for (count = 0; node && count < nr_shrink; count++) {
>> next = rb_next(node);
>> en = rb_entry(node, struct extent_node, rb_node);
>> __release_extent_node(sbi, et, en);
>> node = next;
>> }
>>
>> - return count - atomic_read(&et->node_cnt);
>> + return count;
>> }
>>
>> static void __drop_largest_extent(struct extent_tree *et,
>> @@ -622,6 +623,30 @@ static struct extent_node *__insert_extent_tree(struct f2fs_sb_info *sbi,
>> return en;
>> }
>>
>> +static unsigned int __destroy_extent_node(struct inode *inode,
>> + enum extent_type type)
>> +{
>> + struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>> + struct extent_tree *et = F2FS_I(inode)->extent_tree[type];
>> + unsigned int nr_shrink = type == EX_READ ?
>> + READ_EXTENT_CACHE_SHRINK_NUMBER :
>> + AGE_EXTENT_CACHE_SHRINK_NUMBER;
>> + unsigned int node_cnt = 0;
>> +
>> + if (!et || !atomic_read(&et->node_cnt))
>> + return 0;
>> +
>> + while (atomic_read(&et->node_cnt)) {
>> + write_lock(&et->lock);
>> + node_cnt = __free_extent_tree(sbi, et, nr_shrink);
> should be: node_cnt += __free_extent_tree(sbi, et, nr_shrink); ??
Correct,
>> + write_unlock(&et->lock);
>> + }
>> +
>> + f2fs_bug_on(sbi, atomic_read(&et->node_cnt));
>> +
>> + return node_cnt;
>> +}
>> +
>> static void __update_extent_tree_range(struct inode *inode,
>> struct extent_info *tei, enum extent_type type)
>> {
>> @@ -760,9 +785,6 @@ static void __update_extent_tree_range(struct inode *inode,
>> }
>> }
>>
>> - if (is_inode_flag_set(inode, FI_NO_EXTENT))
>> - __free_extent_tree(sbi, et);
>> -
>> if (et->largest_updated) {
>> et->largest_updated = false;
>> updated = true;
>> @@ -780,6 +802,9 @@ static void __update_extent_tree_range(struct inode *inode,
>> out_read_extent_cache:
>> write_unlock(&et->lock);
>>
>> + if (is_inode_flag_set(inode, FI_NO_EXTENT))
>> + __destroy_extent_node(inode, EX_READ);
>> +
>> if (updated)
>> f2fs_mark_inode_dirty_sync(inode, true);
>> }
>> @@ -942,7 +967,8 @@ static unsigned int __shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink
>> list_for_each_entry_safe(et, next, &eti->zombie_list, list) {
>> if (atomic_read(&et->node_cnt)) {
>> write_lock(&et->lock);
>> - node_cnt += __free_extent_tree(sbi, et);
>> + node_cnt += __free_extent_tree(sbi, et,
>> + nr_shrink - node_cnt - tree_cnt);
>> write_unlock(&et->lock);
>> }
>> f2fs_bug_on(sbi, atomic_read(&et->node_cnt));
> this f2fs_bug_on statment should be removed or omited?
> and the following free tree action can not be do if
> atomic_read(&et->node_cnt) !=0 ?
Yes, will fix this soon, and let me test for a while.
Thanks,
> thanks!
>> @@ -1084,23 +1110,6 @@ unsigned int f2fs_shrink_age_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink
>> return __shrink_extent_tree(sbi, nr_shrink, EX_BLOCK_AGE);
>> }
>>
>> -static unsigned int __destroy_extent_node(struct inode *inode,
>> - enum extent_type type)
>> -{
>> - struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>> - struct extent_tree *et = F2FS_I(inode)->extent_tree[type];
>> - unsigned int node_cnt = 0;
>> -
>> - if (!et || !atomic_read(&et->node_cnt))
>> - return 0;
>> -
>> - write_lock(&et->lock);
>> - node_cnt = __free_extent_tree(sbi, et);
>> - write_unlock(&et->lock);
>> -
>> - return node_cnt;
>> -}
>> -
>> void f2fs_destroy_extent_node(struct inode *inode)
>> {
>> __destroy_extent_node(inode, EX_READ);
>> @@ -1109,7 +1118,6 @@ void f2fs_destroy_extent_node(struct inode *inode)
>>
>> static void __drop_extent_tree(struct inode *inode, enum extent_type type)
>> {
>> - struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>> struct extent_tree *et = F2FS_I(inode)->extent_tree[type];
>> bool updated = false;
>>
>> @@ -1117,7 +1125,6 @@ static void __drop_extent_tree(struct inode *inode, enum extent_type type)
>> return;
>>
>> write_lock(&et->lock);
>> - __free_extent_tree(sbi, et);
>> if (type == EX_READ) {
>> set_inode_flag(inode, FI_NO_EXTENT);
>> if (et->largest.len) {
>> @@ -1126,6 +1133,9 @@ static void __drop_extent_tree(struct inode *inode, enum extent_type type)
>> }
>> }
>> write_unlock(&et->lock);
>> +
>> + __destroy_extent_node(inode, type);
>> +
>> if (updated)
>> f2fs_mark_inode_dirty_sync(inode, true);
>> }
>> --
>> 2.40.1
>>
>> From 3a1b7ec606d6211b2eaf72d148ebe52d38a0bf59 Mon Sep 17 00:00:00 2001
>> From: Chao Yu <chao@...nel.org>
>> Date: Wed, 20 Nov 2024 15:37:22 +0800
>> Subject: [PATCH 2/2] f2fs: add a sysfs node to limit max read extent count
>> per-inode
>>
>> Signed-off-by: Chao Yu <chao@...nel.org>
>> ---
>> Documentation/ABI/testing/sysfs-fs-f2fs | 6 ++++++
>> fs/f2fs/extent_cache.c | 5 ++++-
>> fs/f2fs/f2fs.h | 4 ++++
>> fs/f2fs/sysfs.c | 7 +++++++
>> 4 files changed, 21 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
>> index 513296bb6f29..3e1630c70d8a 100644
>> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
>> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
>> @@ -822,3 +822,9 @@ Description: It controls the valid block ratio threshold not to trigger excessiv
>> for zoned deivces. The initial value of it is 95(%). F2FS will stop the
>> background GC thread from intiating GC for sections having valid blocks
>> exceeding the ratio.
>> +
>> +What: /sys/fs/f2fs/<disk>/max_read_extent_count
>> +Date: November 2024
>> +Contact: "Chao Yu" <chao@...nel.org>
>> +Description: It controls max read extent count for per-inode, the value of threshold
>> + is 10240 by default.
>> diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
>> index 0c0d05f8551a..b08563ad010d 100644
>> --- a/fs/f2fs/extent_cache.c
>> +++ b/fs/f2fs/extent_cache.c
>> @@ -717,7 +717,9 @@ static void __update_extent_tree_range(struct inode *inode,
>> }
>>
>> if (end < org_end && (type != EX_READ ||
>> - org_end - end >= F2FS_MIN_EXTENT_LEN)) {
>> + (org_end - end >= F2FS_MIN_EXTENT_LEN &&
>> + atomic_read(&et->node_cnt) <
>> + sbi->max_read_extent_count))) {
>> if (parts) {
>> __set_extent_info(&ei,
>> end, org_end - end,
>> @@ -1209,6 +1211,7 @@ void f2fs_init_extent_cache_info(struct f2fs_sb_info *sbi)
>> sbi->hot_data_age_threshold = DEF_HOT_DATA_AGE_THRESHOLD;
>> sbi->warm_data_age_threshold = DEF_WARM_DATA_AGE_THRESHOLD;
>> sbi->last_age_weight = LAST_AGE_WEIGHT;
>> + sbi->max_read_extent_count = DEF_MAX_READ_EXTENT_COUNT;
>> }
>>
>> int __init f2fs_create_extent_cache(void)
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index b65b023a588a..6f2cbf4c5740 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -635,6 +635,9 @@ enum {
>> #define DEF_HOT_DATA_AGE_THRESHOLD 262144
>> #define DEF_WARM_DATA_AGE_THRESHOLD 2621440
>>
>> +/* default max read extent count per inode */
>> +#define DEF_MAX_READ_EXTENT_COUNT 10240
>> +
>> /* extent cache type */
>> enum extent_type {
>> EX_READ,
>> @@ -1619,6 +1622,7 @@ struct f2fs_sb_info {
>> /* for extent tree cache */
>> struct extent_tree_info extent_tree[NR_EXTENT_CACHES];
>> atomic64_t allocated_data_blocks; /* for block age extent_cache */
>> + unsigned int max_read_extent_count; /* max read extent count per inode */
>>
>> /* The threshold used for hot and warm data seperation*/
>> unsigned int hot_data_age_threshold;
>> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
>> index bdbf24db667b..d1356c656cac 100644
>> --- a/fs/f2fs/sysfs.c
>> +++ b/fs/f2fs/sysfs.c
>> @@ -787,6 +787,13 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
>> return count;
>> }
>>
>> + if (!strcmp(a->attr.name, "max_read_extent_count")) {
>> + if (t > UINT_MAX)
>> + return -EINVAL;
>> + *ui = (unsigned int)t;
>> + return count;
>> + }
>> +
>> if (!strcmp(a->attr.name, "ipu_policy")) {
>> if (t >= BIT(F2FS_IPU_MAX))
>> return -EINVAL;
>> --
>> 2.40.1
>>
>>
>>
>>> thanks！
>>>>
>>>> + if (need && (excess_cached_nats(sbi) ||
>>>> + !f2fs_available_free_memory(sbi, READ_EXTENT_CACHE) ||
>>>> + !f2fs_available_free_memory(sbi, AGE_EXTENT_CACHE)))
>>>>
>>>> I mean will f2fs_available_free_memory(sbi, {READ,AGE}_EXTENT_CACHE)
>>>> return true if available memory is sufficient?
>>>>
>>>> Thanks,
>>>>
>>>>> trigger the issue in path f2fs_write_node_pages->f2fs_balance_fs_bg(is
>>>>> called directly here).
>>>>> At that time, there were already a lot of extent node cnt.
>>>>> Thanks!
>>>>>>
>>>>>>> 2. Writing back the inode in the normal write-back process will
>>>>>>> release the extent cache, and the problem still occurs. The stack is
>>>>>>> as follows:
>>>>>>
>>>>>> Ditto,
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>>> [H 103098.974356] c2 [<ffffffc008aee8a4>] (rb_erase+0x204/0x334)
>>>>>>> [H 103098.974389] c2 [<ffffffc0088f8fd0>] (__release_extent_node+0xc8/0x168)
>>>>>>> [H 103098.974425] c2 [<ffffffc0088fad74>]
>>>>>>> (f2fs_update_extent_tree_range+0x4a0/0x724)
>>>>>>> [H 103098.974459] c2 [<ffffffc0088fa8c0>] (f2fs_update_extent_cache+0x19c/0x1b0)
>>>>>>> [H 103098.974495] c2 [<ffffffc0088edc70>] (f2fs_outplace_write_data+0x74/0xf0)
>>>>>>> [H 103098.974525] c2 [<ffffffc0088ca834>] (f2fs_do_write_data_page+0x3e4/0x6c8)
>>>>>>> [H 103098.974552] c2 [<ffffffc0088cb150>]
>>>>>>> (f2fs_write_single_data_page+0x478/0xab0)
>>>>>>> [H 103098.974574] c2 [<ffffffc0088d0bd0>] (f2fs_write_cache_pages+0x454/0xaac)
>>>>>>> [H 103098.974596] c2 [<ffffffc0088d0698>] (__f2fs_write_data_pages+0x40c/0x4f0)
>>>>>>> [H 103098.974617] c2 [<ffffffc0088cc860>] (f2fs_write_data_pages+0x30/0x40)
>>>>>>> [H 103098.974645] c2 [<ffffffc0084c0e00>] (do_writepages+0x18c/0x3e8)
>>>>>>> [H 103098.974678] c2 [<ffffffc0086503cc>] (__writeback_single_inode+0x48/0x498)
>>>>>>> [H 103098.974720] c2 [<ffffffc0086562c8>] (writeback_sb_inodes+0x454/0x9b0)
>>>>>>> [H 103098.974754] c2 [<ffffffc008655de8>] (__writeback_inodes_wb+0x198/0x224)
>>>>>>> [H 103098.974788] c2 [<ffffffc008656d0c>] (wb_writeback+0x1c0/0x698)
>>>>>>> [H 103098.974819] c2 [<ffffffc008655614>] (wb_do_writeback+0x420/0x54c)
>>>>>>> [H 103098.974853] c2 [<ffffffc008654f50>] (wb_workfn+0xe4/0x388)
>>>>>>
>>>>
>>
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