I agree that try_get_page() should probably be removed entirely; is there a reason you didn't in v2 of the patch? I'm also curious why you changed try_get_compound_head() into a routine from an inline. If you want to retain try_get_page() it should be an inline as well, especially in its current implementation. William Kucharski > On Aug 11, 2021, at 1:05 AM, John Hubbard <jhubbard@xxxxxxxxxx> wrote: > > try_get_page() is very similar to try_get_compound_head(), and in fact > try_get_page() has fallen a little behind in terms of maintenance: > try_get_compound_head() handles speculative page references more > thoroughly. > > There are only two try_get_page() callsites, so just call > try_get_compound_head() directly from those, and remove try_get_page() > entirely. > > Also, seeing as how this changes try_get_compound_head() into a > non-static function, provide some kerneldoc documentation for it. > > Cc: Christoph Hellwig <hch@xxxxxx> > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx> > --- > arch/s390/mm/fault.c | 2 +- > fs/pipe.c | 2 +- > include/linux/mm.h | 10 +--------- > mm/gup.c | 21 +++++++++++++++++---- > 4 files changed, 20 insertions(+), 15 deletions(-) > > diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c > index 212632d57db9..fe1d2c1dbe3b 100644 > --- a/arch/s390/mm/fault.c > +++ b/arch/s390/mm/fault.c > @@ -822,7 +822,7 @@ void do_secure_storage_access(struct pt_regs *regs) > break; > case KERNEL_FAULT: > page = phys_to_page(addr); > - if (unlikely(!try_get_page(page))) > + if (unlikely(try_get_compound_head(page, 1) == NULL)) > break; > rc = arch_make_page_accessible(page); > put_page(page); > diff --git a/fs/pipe.c b/fs/pipe.c > index 8e6ef62aeb1c..06ba9df37410 100644 > --- a/fs/pipe.c > +++ b/fs/pipe.c > @@ -191,7 +191,7 @@ EXPORT_SYMBOL(generic_pipe_buf_try_steal); > */ > bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf) > { > - return try_get_page(buf->page); > + return try_get_compound_head(buf->page, 1) != NULL; > } > EXPORT_SYMBOL(generic_pipe_buf_get); > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index ce8fc0fd6d6e..cd00d1222235 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1207,15 +1207,7 @@ bool __must_check try_grab_page(struct page *page, unsigned int flags); > __maybe_unused struct page *try_grab_compound_head(struct page *page, int refs, > unsigned int flags); > > - > -static inline __must_check bool try_get_page(struct page *page) > -{ > - page = compound_head(page); > - if (WARN_ON_ONCE(page_ref_count(page) <= 0)) > - return false; > - page_ref_inc(page); > - return true; > -} > +struct page *try_get_compound_head(struct page *page, int refs); > > /** > * folio_put - Decrement the reference count on a folio. > diff --git a/mm/gup.c b/mm/gup.c > index 64798d6b5043..c2d19d370c99 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -62,11 +62,24 @@ static void put_page_refs(struct page *page, int refs) > put_page(page); > } > > -/* > - * Return the compound head page with ref appropriately incremented, > - * or NULL if that failed. > +/** > + * try_get_compound_head() - return the compound head page with refcount > + * appropriately incremented, or NULL if that failed. > + * > + * This handles potential refcount overflow correctly. It also works correctly > + * for various lockless get_user_pages()-related callers, due to the use of > + * page_cache_add_speculative(). > + * > + * Even though the name includes "compound_head", this function is still > + * appropriate for callers that have a non-compound @page to get. > + * > + * @page: pointer to page to be gotten > + * @refs: the value to add to the page's refcount > + * > + * Return: head page (with refcount appropriately incremented) for success, or > + * NULL upon failure. > */ > -static inline struct page *try_get_compound_head(struct page *page, int refs) > +struct page *try_get_compound_head(struct page *page, int refs) > { > struct page *head = compound_head(page); > > -- > 2.32.0 > >