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Thu, 10 Oct 2024 12:16:08 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id IRE0AIjFB2cLPQAAD6G6ig (envelope-from ); Thu, 10 Oct 2024 12:16:08 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 6731EA08A2; Thu, 10 Oct 2024 14:16:07 +0200 (CEST) Date: Thu, 10 Oct 2024 14:16:07 +0200 From: Jan Kara To: Ye Bin Cc: viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, yebin10@huawei.com, zhangxiaoxu5@huawei.com Subject: Re: [PATCH 2/3] sysctl: add support for drop_caches for individual filesystem Message-ID: <20241010121607.54ttcmdfmh7ywho7@quack3> References: <20241010112543.1609648-1-yebin@huaweicloud.com> <20241010112543.1609648-3-yebin@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241010112543.1609648-3-yebin@huaweicloud.com> X-Rspamd-Queue-Id: 0FE451FE42 X-Spam-Level: X-Spamd-Result: default: False [-4.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_RHS_NOT_FQDN(0.50)[]; R_DKIM_ALLOW(-0.20)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; MISSING_XM_UA(0.00)[]; RCPT_COUNT_SEVEN(0.00)[8]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:email]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCVD_COUNT_THREE(0.00)[3]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; RCVD_TLS_LAST(0.00)[]; DKIM_TRACE(0.00)[suse.cz:+] X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Action: no action X-Spam-Score: -4.01 X-Spam-Flag: NO On Thu 10-10-24 19:25:42, Ye Bin wrote: > From: Ye Bin > > In order to better analyze the issue of file system uninstallation caused > by kernel module opening files, it is necessary to perform dentry recycling I don't quite understand the use case you mention here. Can you explain it a bit more (that being said I've needed dropping caches for a particular sb myself a few times for debugging purposes so I generally agree it is a useful feature). > 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 > --- > 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; I think specifying bdev major & minor number is not a great interface these days. In particular for filesystems which are not bdev based such as NFS. I think specifying path to some file/dir in the filesystem is nicer and you can easily resolve that to sb here as well. Honza -- Jan Kara SUSE Labs, CR