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author | Jason Gunthorpe <jgg@nvidia.com> | 2020-12-14 19:05:51 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-12-15 12:13:39 -0800 |
commit | 4509b42c38963f495b49aa50209c34337286ecbe (patch) | |
tree | f5da3e07162977ca4e9e80aca0455ac114689793 /mm | |
parent | 52650c8b466bac399aec213c61d74bfe6f7af1a4 (diff) | |
download | linux-stable-4509b42c38963f495b49aa50209c34337286ecbe.tar.gz linux-stable-4509b42c38963f495b49aa50209c34337286ecbe.tar.bz2 linux-stable-4509b42c38963f495b49aa50209c34337286ecbe.zip |
mm/gup: combine put_compound_head() and unpin_user_page()
These functions accomplish the same thing but have different
implementations.
unpin_user_page() has a bug where it calls mod_node_page_state() after
calling put_page() which creates a risk that the page could have been
hot-uplugged from the system.
Fix this by using put_compound_head() as the only implementation.
__unpin_devmap_managed_user_page() and related can be deleted as well in
favour of the simpler, but slower, version in put_compound_head() that has
an extra atomic page_ref_sub, but always calls put_page() which internally
contains the special devmap code.
Move put_compound_head() to be directly after try_grab_compound_head() so
people can find it in future.
Link: https://lkml.kernel.org/r/0-v1-6730d4ee0d32+40e6-gup_combine_put_jgg@nvidia.com
Fixes: 1970dc6f5226 ("mm/gup: /proc/vmstat: pin_user_pages (FOLL_PIN) reporting")
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
CC: Joao Martins <joao.m.martins@oracle.com>
CC: Jonathan Corbet <corbet@lwn.net>
CC: Dan Williams <dan.j.williams@intel.com>
CC: Dave Chinner <david@fromorbit.com>
CC: Christoph Hellwig <hch@infradead.org>
CC: Jane Chu <jane.chu@oracle.com>
CC: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
CC: Michal Hocko <mhocko@suse.com>
CC: Mike Kravetz <mike.kravetz@oracle.com>
CC: Shuah Khan <shuah@kernel.org>
CC: Muchun Song <songmuchun@bytedance.com>
CC: Vlastimil Babka <vbabka@suse.cz>
CC: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/gup.c | 103 |
1 files changed, 23 insertions, 80 deletions
@@ -123,6 +123,28 @@ static __maybe_unused struct page *try_grab_compound_head(struct page *page, return NULL; } +static void put_compound_head(struct page *page, int refs, unsigned int flags) +{ + if (flags & FOLL_PIN) { + mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED, + refs); + + if (hpage_pincount_available(page)) + hpage_pincount_sub(page, refs); + else + refs *= GUP_PIN_COUNTING_BIAS; + } + + VM_BUG_ON_PAGE(page_ref_count(page) < refs, page); + /* + * Calling put_page() for each ref is unnecessarily slow. Only the last + * ref needs a put_page(). + */ + if (refs > 1) + page_ref_sub(page, refs - 1); + put_page(page); +} + /** * try_grab_page() - elevate a page's refcount by a flag-dependent amount * @@ -177,41 +199,6 @@ bool __must_check try_grab_page(struct page *page, unsigned int flags) return true; } -#ifdef CONFIG_DEV_PAGEMAP_OPS -static bool __unpin_devmap_managed_user_page(struct page *page) -{ - int count, refs = 1; - - if (!page_is_devmap_managed(page)) - return false; - - if (hpage_pincount_available(page)) - hpage_pincount_sub(page, 1); - else - refs = GUP_PIN_COUNTING_BIAS; - - count = page_ref_sub_return(page, refs); - - mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED, 1); - /* - * devmap page refcounts are 1-based, rather than 0-based: if - * refcount is 1, then the page is free and the refcount is - * stable because nobody holds a reference on the page. - */ - if (count == 1) - free_devmap_managed_page(page); - else if (!count) - __put_page(page); - - return true; -} -#else -static bool __unpin_devmap_managed_user_page(struct page *page) -{ - return false; -} -#endif /* CONFIG_DEV_PAGEMAP_OPS */ - /** * unpin_user_page() - release a dma-pinned page * @page: pointer to page to be released @@ -223,28 +210,7 @@ static bool __unpin_devmap_managed_user_page(struct page *page) */ void unpin_user_page(struct page *page) { - int refs = 1; - - page = compound_head(page); - - /* - * For devmap managed pages we need to catch refcount transition from - * GUP_PIN_COUNTING_BIAS to 1, when refcount reach one it means the - * page is free and we need to inform the device driver through - * callback. See include/linux/memremap.h and HMM for details. - */ - if (__unpin_devmap_managed_user_page(page)) - return; - - if (hpage_pincount_available(page)) - hpage_pincount_sub(page, 1); - else - refs = GUP_PIN_COUNTING_BIAS; - - if (page_ref_sub_and_test(page, refs)) - __put_page(page); - - mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED, 1); + put_compound_head(compound_head(page), 1, FOLL_PIN); } EXPORT_SYMBOL(unpin_user_page); @@ -2009,29 +1975,6 @@ EXPORT_SYMBOL(get_user_pages_unlocked); * This code is based heavily on the PowerPC implementation by Nick Piggin. */ #ifdef CONFIG_HAVE_FAST_GUP - -static void put_compound_head(struct page *page, int refs, unsigned int flags) -{ - if (flags & FOLL_PIN) { - mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED, - refs); - - if (hpage_pincount_available(page)) - hpage_pincount_sub(page, refs); - else - refs *= GUP_PIN_COUNTING_BIAS; - } - - VM_BUG_ON_PAGE(page_ref_count(page) < refs, page); - /* - * Calling put_page() for each ref is unnecessarily slow. Only the last - * ref needs a put_page(). - */ - if (refs > 1) - page_ref_sub(page, refs - 1); - put_page(page); -} - #ifdef CONFIG_GUP_GET_PTE_LOW_HIGH /* |