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Message-ID: <CAHJ8P3LD-9D91p6gtT1DpmrL=JpuuG8HhtgPpZ7uQELgr0FtrA@mail.gmail.com>
Date: Wed, 20 Nov 2024 17:19:05 +0800
From: Zhiguo Niu <niuzhiguo84@...il.com>
To: Chao Yu <chao@...nel.org>
Cc: 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
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); ??
> + 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 ?
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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