forked from mirrors/linux
566d774a11
An upcoming patch requires subtracting a large chunk of refcounts from a page, and checking what the resulting refcount is. This is a little different than the usual "check for zero refcount" that many of the page ref functions already do. However, it is similar to a few other routines that (like this one) are generally useful for things such as 1-based refcounting. Add page_ref_sub_return(), that subtracts a chunk of refcounts atomically, and returns an atomic snapshot of the result. Signed-off-by: John Hubbard <jhubbard@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Jan Kara <jack@suse.cz> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Ira Weiny <ira.weiny@intel.com> Cc: Jérôme Glisse <jglisse@redhat.com> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@infradead.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Vlastimil Babka <vbabka@suse.cz> Link: http://lkml.kernel.org/r/20200211001536.1027652-4-jhubbard@nvidia.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
192 lines
5.2 KiB
C
192 lines
5.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_PAGE_REF_H
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#define _LINUX_PAGE_REF_H
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#include <linux/atomic.h>
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#include <linux/mm_types.h>
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#include <linux/page-flags.h>
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#include <linux/tracepoint-defs.h>
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extern struct tracepoint __tracepoint_page_ref_set;
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extern struct tracepoint __tracepoint_page_ref_mod;
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extern struct tracepoint __tracepoint_page_ref_mod_and_test;
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extern struct tracepoint __tracepoint_page_ref_mod_and_return;
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extern struct tracepoint __tracepoint_page_ref_mod_unless;
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extern struct tracepoint __tracepoint_page_ref_freeze;
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extern struct tracepoint __tracepoint_page_ref_unfreeze;
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#ifdef CONFIG_DEBUG_PAGE_REF
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/*
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* Ideally we would want to use the trace_<tracepoint>_enabled() helper
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* functions. But due to include header file issues, that is not
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* feasible. Instead we have to open code the static key functions.
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*
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* See trace_##name##_enabled(void) in include/linux/tracepoint.h
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*/
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#define page_ref_tracepoint_active(t) static_key_false(&(t).key)
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extern void __page_ref_set(struct page *page, int v);
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extern void __page_ref_mod(struct page *page, int v);
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extern void __page_ref_mod_and_test(struct page *page, int v, int ret);
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extern void __page_ref_mod_and_return(struct page *page, int v, int ret);
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extern void __page_ref_mod_unless(struct page *page, int v, int u);
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extern void __page_ref_freeze(struct page *page, int v, int ret);
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extern void __page_ref_unfreeze(struct page *page, int v);
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#else
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#define page_ref_tracepoint_active(t) false
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static inline void __page_ref_set(struct page *page, int v)
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{
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}
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static inline void __page_ref_mod(struct page *page, int v)
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{
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}
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static inline void __page_ref_mod_and_test(struct page *page, int v, int ret)
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{
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}
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static inline void __page_ref_mod_and_return(struct page *page, int v, int ret)
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{
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}
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static inline void __page_ref_mod_unless(struct page *page, int v, int u)
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{
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}
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static inline void __page_ref_freeze(struct page *page, int v, int ret)
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{
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}
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static inline void __page_ref_unfreeze(struct page *page, int v)
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{
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}
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#endif
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static inline int page_ref_count(struct page *page)
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{
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return atomic_read(&page->_refcount);
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}
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static inline int page_count(struct page *page)
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{
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return atomic_read(&compound_head(page)->_refcount);
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}
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static inline void set_page_count(struct page *page, int v)
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{
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atomic_set(&page->_refcount, v);
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if (page_ref_tracepoint_active(__tracepoint_page_ref_set))
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__page_ref_set(page, v);
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}
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/*
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* Setup the page count before being freed into the page allocator for
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* the first time (boot or memory hotplug)
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*/
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static inline void init_page_count(struct page *page)
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{
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set_page_count(page, 1);
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}
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static inline void page_ref_add(struct page *page, int nr)
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{
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atomic_add(nr, &page->_refcount);
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if (page_ref_tracepoint_active(__tracepoint_page_ref_mod))
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__page_ref_mod(page, nr);
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}
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static inline void page_ref_sub(struct page *page, int nr)
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{
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atomic_sub(nr, &page->_refcount);
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if (page_ref_tracepoint_active(__tracepoint_page_ref_mod))
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__page_ref_mod(page, -nr);
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}
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static inline int page_ref_sub_return(struct page *page, int nr)
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{
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int ret = atomic_sub_return(nr, &page->_refcount);
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if (page_ref_tracepoint_active(__tracepoint_page_ref_mod_and_return))
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__page_ref_mod_and_return(page, -nr, ret);
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return ret;
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}
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static inline void page_ref_inc(struct page *page)
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{
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atomic_inc(&page->_refcount);
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if (page_ref_tracepoint_active(__tracepoint_page_ref_mod))
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__page_ref_mod(page, 1);
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}
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static inline void page_ref_dec(struct page *page)
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{
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atomic_dec(&page->_refcount);
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if (page_ref_tracepoint_active(__tracepoint_page_ref_mod))
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__page_ref_mod(page, -1);
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}
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static inline int page_ref_sub_and_test(struct page *page, int nr)
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{
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int ret = atomic_sub_and_test(nr, &page->_refcount);
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if (page_ref_tracepoint_active(__tracepoint_page_ref_mod_and_test))
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__page_ref_mod_and_test(page, -nr, ret);
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return ret;
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}
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static inline int page_ref_inc_return(struct page *page)
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{
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int ret = atomic_inc_return(&page->_refcount);
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if (page_ref_tracepoint_active(__tracepoint_page_ref_mod_and_return))
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__page_ref_mod_and_return(page, 1, ret);
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return ret;
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}
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static inline int page_ref_dec_and_test(struct page *page)
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{
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int ret = atomic_dec_and_test(&page->_refcount);
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if (page_ref_tracepoint_active(__tracepoint_page_ref_mod_and_test))
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__page_ref_mod_and_test(page, -1, ret);
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return ret;
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}
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static inline int page_ref_dec_return(struct page *page)
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{
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int ret = atomic_dec_return(&page->_refcount);
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if (page_ref_tracepoint_active(__tracepoint_page_ref_mod_and_return))
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__page_ref_mod_and_return(page, -1, ret);
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return ret;
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}
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static inline int page_ref_add_unless(struct page *page, int nr, int u)
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{
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int ret = atomic_add_unless(&page->_refcount, nr, u);
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if (page_ref_tracepoint_active(__tracepoint_page_ref_mod_unless))
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__page_ref_mod_unless(page, nr, ret);
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return ret;
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}
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static inline int page_ref_freeze(struct page *page, int count)
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{
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int ret = likely(atomic_cmpxchg(&page->_refcount, count, 0) == count);
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if (page_ref_tracepoint_active(__tracepoint_page_ref_freeze))
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__page_ref_freeze(page, count, ret);
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return ret;
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}
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static inline void page_ref_unfreeze(struct page *page, int count)
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{
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VM_BUG_ON_PAGE(page_count(page) != 0, page);
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VM_BUG_ON(count == 0);
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atomic_set_release(&page->_refcount, count);
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if (page_ref_tracepoint_active(__tracepoint_page_ref_unfreeze))
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__page_ref_unfreeze(page, count);
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}
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#endif
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