On 2024-10-10 19:25:42+0800, Ye Bin wrote:
> From: Ye Bin <yebin10@xxxxxxxxxx>
>
> In order to better analyze the issue of file system uninstallation caused
> by kernel module opening files, it is necessary to perform dentry recycling
> on a single file system. But now, apart from global dentry recycling, it is
> not supported to do dentry recycling on a single file system separately.
> This feature has usage scenarios in problem localization scenarios.At the
> same time, it also provides users with a slightly fine-grained
> pagecache/entry recycling mechanism.
> This patch supports the recycling of pagecache/entry for individual file
> systems.
>
> Signed-off-by: Ye Bin <yebin10@xxxxxxxxxx>
> ---
> fs/drop_caches.c | 43 +++++++++++++++++++++++++++++++++++++++++++
> include/linux/mm.h | 2 ++
> kernel/sysctl.c | 9 +++++++++
> 3 files changed, 54 insertions(+)
>
> diff --git a/fs/drop_caches.c b/fs/drop_caches.c
> index d45ef541d848..99d412cf3e52 100644
> --- a/fs/drop_caches.c
> +++ b/fs/drop_caches.c
> @@ -77,3 +77,46 @@ int drop_caches_sysctl_handler(const struct ctl_table *table, int write,
> }
> return 0;
> }
> +
> +int drop_fs_caches_sysctl_handler(const struct ctl_table *table, int write,
> + void *buffer, size_t *length, loff_t *ppos)
> +{
> + unsigned int major, minor;
> + unsigned int ctl;
> + struct super_block *sb;
> + static int stfu;
> +
> + if (!write)
> + return 0;
> +
> + if (sscanf(buffer, "%u:%u:%u", &major, &minor, &ctl) != 3)
> + return -EINVAL;
> +
> + if (ctl < *((int *)table->extra1) || ctl > *((int *)table->extra2))
> + return -EINVAL;
> +
> + sb = user_get_super(MKDEV(major, minor), false);
> + if (!sb)
> + return -EINVAL;
> +
> + if (ctl & 1) {
BIT(0)
> + lru_add_drain_all();
> + drop_pagecache_sb(sb, NULL);
> + count_vm_event(DROP_PAGECACHE);
> + }
> +
> + if (ctl & 2) {
> + shrink_dcache_sb(sb);
> + shrink_icache_sb(sb);
> + count_vm_event(DROP_SLAB);
> + }
> +
> + drop_super(sb);
> +
> + if (!stfu)
> + pr_info("%s (%d): drop_fs_caches: %u:%u:%d\n", current->comm,
> + task_pid_nr(current), major, minor, ctl);
> + stfu |= ctl & 4;
This looks very weird. I guess it's already in the original
drop_caches_sysctl_handler().
> +
> + return 0;
> +}
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 344541f8cba0..43079478296f 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3788,6 +3788,8 @@ extern bool process_shares_mm(struct task_struct *p, struct mm_struct *mm);
> extern int sysctl_drop_caches;
> int drop_caches_sysctl_handler(const struct ctl_table *, int, void *, size_t *,
> loff_t *);
> +int drop_fs_caches_sysctl_handler(const struct ctl_table *table, int write,
> + void *buffer, size_t *length, loff_t *ppos);
> #endif
>
> void drop_slab(void);
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 79e6cb1d5c48..d434cbe10e47 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -2101,6 +2101,15 @@ static struct ctl_table vm_table[] = {
Sooner or later this table should move out of kernel/sysctl.c and into a
subsystem-specific file.
This also means the handler doesn't need to be exported.
> .extra1 = SYSCTL_ONE,
> .extra2 = SYSCTL_FOUR,
> },
> + {
> + .procname = "drop_fs_caches",
> + .data = NULL,
NULL is already the default.
> + .maxlen = 256,
The maxlen field refers to the data field.
As there is no data, there should be no maxlen.
> + .mode = 0200,
> + .proc_handler = drop_fs_caches_sysctl_handler,
> + .extra1 = SYSCTL_ONE,
> + .extra2 = SYSCTL_FOUR,
These extras are meant as parameters for generic handlers.
Inlining the limits into your hander makes it much clearer.
> + },
> {
> .procname = "page_lock_unfairness",
> .data = &sysctl_page_lock_unfairness,
> --
> 2.31.1
>
