Re: [PATCH v8 3/3] fuse: add default_request_timeout and max_request_timeout sysctls

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On 10/11/24 21:13, Joanne Koong wrote:
> Introduce two new sysctls, "default_request_timeout" and
> "max_request_timeout". These control how long (in minutes) a server can
> take to reply to a request. If the server does not reply by the timeout,
> then the connection will be aborted.
> 
> "default_request_timeout" sets the default timeout if no timeout is
> specified by the fuse server on mount. 0 (default) indicates no default
> timeout should be enforced. If the server did specify a timeout, then
> default_request_timeout will be ignored.
> 
> "max_request_timeout" sets the max amount of time the server may take to
> reply to a request. 0 (default) indicates no maximum timeout. If
> max_request_timeout is set and the fuse server attempts to set a
> timeout greater than max_request_timeout, the system will use
> max_request_timeout as the timeout. Similarly, if default_request_timeout
> is greater than max_request_timeout, the system will use
> max_request_timeout as the timeout. If the server does not request a
> timeout and default_request_timeout is set to 0 but max_request_timeout
> is set, then the timeout will be max_request_timeout.
> 
> Please note that these timeouts are not 100% precise. The request may
> take an extra FUSE_TIMEOUT_TIMER_FREQ seconds beyond the set max timeout
> due to how it's internally implemented.
> 
> $ sysctl -a | grep fuse.default_request_timeout
> fs.fuse.default_request_timeout = 0
> 
> $ echo 65536 | sudo tee /proc/sys/fs/fuse/default_request_timeout
> tee: /proc/sys/fs/fuse/default_request_timeout: Invalid argument
> 
> $ echo 65535 | sudo tee /proc/sys/fs/fuse/default_request_timeout
> 65535
> 
> $ sysctl -a | grep fuse.default_request_timeout
> fs.fuse.default_request_timeout = 65535
> 
> $ echo 0 | sudo tee /proc/sys/fs/fuse/default_request_timeout
> 0
> 
> $ sysctl -a | grep fuse.default_request_timeout
> fs.fuse.default_request_timeout = 0
> 
> Signed-off-by: Joanne Koong <joannelkoong@xxxxxxxxx>
> ---
>  Documentation/admin-guide/sysctl/fs.rst | 27 +++++++++++++++++++++++++
>  fs/fuse/fuse_i.h                        | 10 +++++++++
>  fs/fuse/inode.c                         | 16 +++++++++++++--
>  fs/fuse/sysctl.c                        | 20 ++++++++++++++++++
>  4 files changed, 71 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/admin-guide/sysctl/fs.rst b/Documentation/admin-guide/sysctl/fs.rst
> index fa25d7e718b3..790a34291467 100644
> --- a/Documentation/admin-guide/sysctl/fs.rst
> +++ b/Documentation/admin-guide/sysctl/fs.rst
> @@ -342,3 +342,30 @@ filesystems:
>  ``/proc/sys/fs/fuse/max_pages_limit`` is a read/write file for
>  setting/getting the maximum number of pages that can be used for servicing
>  requests in FUSE.
> +
> +``/proc/sys/fs/fuse/default_request_timeout`` is a read/write file for
> +setting/getting the default timeout (in minutes) for a fuse server to
> +reply to a kernel-issued request in the event where the server did not
> +specify a timeout at mount. If the server set a timeout,
> +then default_request_timeout will be ignored.  The default
> +"default_request_timeout" is set to 0. 0 indicates a no-op (eg
> +requests will not have a default request timeout set if no timeout was
> +specified by the server).
> +
> +``/proc/sys/fs/fuse/max_request_timeout`` is a read/write file for
> +setting/getting the maximum timeout (in minutes) for a fuse server to
> +reply to a kernel-issued request. A value greater than 0 automatically opts
> +the server into a timeout that will be at most "max_request_timeout", even if
> +the server did not specify a timeout and default_request_timeout is set to 0.
> +If max_request_timeout is greater than 0 and the server set a timeout greater
> +than max_request_timeout or default_request_timeout is set to a value greater
> +than max_request_timeout, the system will use max_request_timeout as the
> +timeout. 0 indicates a no-op (eg requests will not have an upper bound on the
> +timeout and if the server did not request a timeout and default_request_timeout
> +was not set, there will be no timeout).
> +
> +Please note that for the timeout options, if the server does not respond to
> +the request by the time the timeout elapses, then the connection to the fuse
> +server will be aborted. Please also note that the timeouts are not 100%
> +precise (eg you may set 10 minutes but the timeout may kick in after 11
> +minutes).
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index ef4558c2c44e..28d9230f4fcb 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -46,6 +46,16 @@
>  
>  /** Maximum of max_pages received in init_out */
>  extern unsigned int fuse_max_pages_limit;
> +/*
> + * Default timeout (in minutes) for the server to reply to a request
> + * before the connection is aborted, if no timeout was specified on mount.
> + */
> +extern unsigned int fuse_default_req_timeout;
> +/*
> + * Max timeout (in minutes) for the server to reply to a request before
> + * the connection is aborted.
> + */
> +extern unsigned int fuse_max_req_timeout;
>  
>  /** List of active connections */
>  extern struct list_head fuse_conn_list;
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index a78aac76b942..d97dde59eac3 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -36,6 +36,9 @@ DEFINE_MUTEX(fuse_mutex);
>  static int set_global_limit(const char *val, const struct kernel_param *kp);
>  
>  unsigned int fuse_max_pages_limit = 256;
> +/* default is no timeout */
> +unsigned int fuse_default_req_timeout = 0;
> +unsigned int fuse_max_req_timeout = 0;
>  
>  unsigned max_user_bgreq;
>  module_param_call(max_user_bgreq, set_global_limit, param_get_uint,
> @@ -1701,8 +1704,17 @@ EXPORT_SYMBOL_GPL(fuse_init_fs_context_submount);
>  
>  static void fuse_init_fc_timeout(struct fuse_conn *fc, struct fuse_fs_context *ctx)
>  {
> -	if (ctx->req_timeout) {
> -		if (check_mul_overflow(ctx->req_timeout * 60, HZ, &fc->timeout.req_timeout))
> +	unsigned int timeout = ctx->req_timeout ?: fuse_default_req_timeout;
> +
> +	if (fuse_max_req_timeout) {
> +		if (!timeout)
> +			timeout = fuse_max_req_timeout;

Hmm, so 'max' might be used as 'min' as well. Isn't that a bit confusing?


> +		else
> +			timeout = min(timeout, fuse_max_req_timeout)> +	}
> +
> +	if (timeout) {
> +		if (check_mul_overflow(timeout * 60, HZ, &fc->timeout.req_timeout))
>  			fc->timeout.req_timeout = U32_MAX;
>  		timer_setup(&fc->timeout.timer, fuse_check_timeout, 0);
>  		mod_timer(&fc->timeout.timer, jiffies + FUSE_TIMEOUT_TIMER_FREQ);
> diff --git a/fs/fuse/sysctl.c b/fs/fuse/sysctl.c
> index b272bb333005..e70b5269c16d 100644
> --- a/fs/fuse/sysctl.c
> +++ b/fs/fuse/sysctl.c
> @@ -13,6 +13,8 @@ static struct ctl_table_header *fuse_table_header;
>  /* Bound by fuse_init_out max_pages, which is a u16 */
>  static unsigned int sysctl_fuse_max_pages_limit = 65535;
>  
> +static unsigned int sysctl_fuse_max_req_timeout_limit = U16_MAX;
> +
>  static struct ctl_table fuse_sysctl_table[] = {
>  	{
>  		.procname	= "max_pages_limit",
> @@ -23,6 +25,24 @@ static struct ctl_table fuse_sysctl_table[] = {
>  		.extra1		= SYSCTL_ONE,
>  		.extra2		= &sysctl_fuse_max_pages_limit,
>  	},
> +	{
> +		.procname	= "default_request_timeout",
> +		.data		= &fuse_default_req_timeout,
> +		.maxlen		= sizeof(fuse_default_req_timeout),
> +		.mode		= 0644,
> +		.proc_handler	= proc_douintvec_minmax,
> +		.extra1         = SYSCTL_ZERO,

There is slight whitespace issue here - spaces instead of tabs.


> +		.extra2		= &sysctl_fuse_max_req_timeout_limit,
> +	},
> +	{
> +		.procname	= "max_request_timeout",
> +		.data		= &fuse_max_req_timeout,
> +		.maxlen		= sizeof(fuse_max_req_timeout),
> +		.mode		= 0644,
> +		.proc_handler	= proc_douintvec_minmax,
> +		.extra1         = SYSCTL_ZERO,

And here.

> +		.extra2		= &sysctl_fuse_max_req_timeout_limit,
> +	},
>  };
>  
>  int fuse_sysctl_register(void)

Reviewed-by: Bernd Schubert <bschubert@xxxxxxx>




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