Re: [PATCH v3 0/3] add support for drop_caches for individual filesystem

["yebin (H)" <yebin10@huawei.com>]

On 2026/2/27 14:50, Qi Zheng wrote:
>
>
> On 2/27/26 2:39 PM, yebin (H) wrote:
>>
>>
>> On 2026/2/27 11:31, Muchun Song wrote:
>>>
>>>
>>>> On Feb 27, 2026, at 10:55, Ye Bin <yebin@huaweicloud.com> wrote:
>>>>
>>>> From: Ye Bin <yebin10@huawei.com>
>>>>
>>>> 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.
>>>
>>> Would shrinker-debugfs satisfy your needs (See Documentation/admin-
>>> guide/mm/shrinker_debugfs.rst)?
>>>
>>> Thanks,
>>> Muchun
>>>
>> Thank you for the reminder. The reclamation of dentries and nodes can
>> meet my needs. However, the reclamation of the page cache alone does
>> not satisfy my requirements. I have reviewed the code of
>> shrinker_debugfs_scan_write() and found that it does not support batch
>> deletion of all dentries/inode for all nodes/memcgs,instead, users
>> need to traverse through them one by one, which is not very
>> convenient. Based on my previous experience, I have always performed
>> dentry/inode reclamation at the file system level.
>
> Using shrinker-debugfs allows users to specify the size of a single
> reclaim cycle (nr_to_scan), which controls the strength of each reclaim
> cycle to adapt to different workloads. Can the new drop_fs_caches
> support a similar approach?
>
> Thanks,
> Qi
>
"drop_fs_caches" is similar to "drop_caches," but it only operates on 
the specified file system. It does not support specifying the number of 
pages to scan (nr_to_scan).
>>
>> Thanks,
>> Ye Bin
>>>> 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 patchset supports the recycling of pagecache/entry for
>>>> individual file
>>>> systems.
>>>>
>>>> Diff v3 vs v2
>>>> 1. Introduce introduce drop_sb_dentry_inode() helper instead of
>>>> reclaim_dcache_sb()/reclaim_icache_sb() helper for reclaim
>>>> dentry/inode.
>>>> 2. Fixing compilation issues in specific architectures and
>>>> configurations.
>>>>
>>>> Diff v2 vs v1:
>>>> 1. Fix possible live lock for shrink_icache_sb().
>>>> 2. Introduce reclaim_dcache_sb() for reclaim dentry.
>>>> 3. Fix potential deadlocks as follows:
>>>> https://lore.kernel.org/linux-
>>>> fsdevel/00000000000098f75506153551a1@google.com/
>>>> After some consideration, it was decided that this feature would
>>>> primarily
>>>> be used for debugging purposes. Instead of adding a new IOCTL
>>>> command, the
>>>> task_work mechanism was employed to address potential deadlock issues.
>>>>
>>>> Ye Bin (3):
>>>>   mm/vmscan: introduce drop_sb_dentry_inode() helper
>>>>   sysctl: add support for drop_caches for individual filesystem
>>>>   Documentation: add instructions for using 'drop_fs_caches sysctl'
>>>>     sysctl
>>>>
>>>> Documentation/admin-guide/sysctl/vm.rst |  44 +++++++++
>>>> fs/drop_caches.c                        | 125 ++++++++++++++++++++++++
>>>> include/linux/mm.h                      |   1 +
>>>> mm/internal.h                           |   3 +
>>>> mm/shrinker.c                           |   4 +-
>>>> mm/vmscan.c                             |  50 ++++++++++
>>>> 6 files changed, 225 insertions(+), 2 deletions(-)
>>>>
>>>> --
>>>> 2.34.1
>>>>
>>>
>>> .
>>>
>
> .
>