Re: [RESEND4, PATCH 1/2] fuse: retrieve: cap requested size to negotiated max_write

Kirill Smelkov
2019-04-24T18:10:10Z

On Wed, Apr 24, 2019 at 05:02:42PM +0200, Miklos Szeredi wrote:
> On Wed, Apr 24, 2019 at 4:22 PM Kirill Smelkov <kirr@nexedi.com> wrote:
> > - FUSE_PRECISE_INVAL_DATA:
> >
> > --- b/include/uapi/linux/fuse.h
> > +++ b/include/uapi/linux/fuse.h
> > @@ -266,7 +266,7 @@
> > * FUSE_MAX_PAGES: init_out.max_pages contains the max number of req pages
> > * FUSE_CACHE_SYMLINKS: cache READLINK responses
> > * FUSE_NO_OPENDIR_SUPPORT: kernel supports zero-message opendir
> > - * FUSE_PRECISE_INVAL_DATA: filesystem is fully responsible for data cache invalidation
> > + * FUSE_PRECISE_INVAL_DATA: filesystem is fully responsible for invalidation
> > */
> > #define FUSE_ASYNC_READ (1 << 0)
> > #define FUSE_POSIX_LOCKS (1 << 1)
> >
> > the "data cache" in "for data cache invalidation" has particular meaning
> > and semantic: the filesystem promises to explicitly invalidate data of
>
> Right; better name: FUSE_EXPLICIT_INVAL_DATA. Will push fixed version.

- * FUSE_PRECISE_INVAL_DATA: filesystem is fully responsible for invalidation
+ * FUSE_EXPLICIT_INVAL_DATA: only invalidate cached pages on explicit request

...

/** Filesystem is fully reponsible for page cache invalidation. */
- unsigned precise_inval_data:1;
+ unsigned explicit_inval_data:1;

Ok, let it be this way.

> > Your amendment for FOPEN_STREAM in uapi/linux/fuse.h (see above) also
> > suggests that it is better to be more explicit in that file.
> >
> > --- b/fs/fuse/inode.c
> > +++ b/fs/fuse/inode.c
> > @@ -913,13 +913,8 @@
> > fc->dont_mask = 1;
> > if (arg->flags & FUSE_AUTO_INVAL_DATA)
> > fc->auto_inval_data = 1;
> > - if (arg->flags & FUSE_PRECISE_INVAL_DATA)
> > + else if (arg->flags & FUSE_PRECISE_INVAL_DATA)
> > fc->precise_inval_data = 1;
> > - if (fc->auto_inval_data && fc->precise_inval_data) {
> > - pr_warn("filesystem requested both auto and "
> > - "precise cache control - using auto\n");
> > - fc->precise_inval_data = 0;
> > - }
> > if (arg->flags & FUSE_DO_READDIRPLUS) {
> > fc->do_readdirplus = 1;
> > if (arg->flags & FUSE_READDIRPLUS_AUTO)
> >
> > Even though it is ok for me personally (I could be careful and use only
> > FUSE_PRECISE_INVAL_DATA) I still think usage of both "auto" and "precise"
> > invalidation modes deserves a warning. It is only at filesystem init time. What
> > is the reason not to print it?
>
> The warning makes no sense. It should either be failure or silent override.

Ok.

> > - "fuse: retrieve: cap requested size to negotiated max_write"
> >
> > Signed-off-by: Kirill Smelkov <kirr@nexedi.com>
> > Cc: Han-Wen Nienhuys <hanwen@google.com>
> > Cc: Jakob Unterwurzacher <jakobunt@gmail.com>
> > -Cc: <stable@vger.kernel.org> # v2.6.36+
> >
> > what is the reason not to include this patch into stable series?
>
> This doens't fix any bugs out there, but there is a slight chance of
> regression (so it might possibly have to be reverted in the future) so
> it absolutely makes no sense to backport it to stable.

Ok.

Thanks again for tossing the patches,

Kirill