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| author | Joonsoo Kim <iamjoonsoo.kim@lge.com> | 2016-05-20 02:10:49 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-05-20 04:12:14 +0200 |
| commit | 0139aa7b7fa12ceef095d99dc36606a5b10ab83a (patch) | |
| tree | 94da74f2f79911a11a3c7c34f73ba971dec41a7e /Documentation/vm | |
| parent | mm/page_ref: use page_ref helper instead of direct modification of _count (diff) | |
| download | linux-0139aa7b7fa12ceef095d99dc36606a5b10ab83a.tar.xz linux-0139aa7b7fa12ceef095d99dc36606a5b10ab83a.zip | |
mm: rename _count, field of the struct page, to _refcount
Many developers already know that field for reference count of the
struct page is _count and atomic type. They would try to handle it
directly and this could break the purpose of page reference count
tracepoint. To prevent direct _count modification, this patch rename it
to _refcount and add warning message on the code. After that, developer
who need to handle reference count will find that field should not be
accessed directly.
[akpm@linux-foundation.org: fix comments, per Vlastimil]
[akpm@linux-foundation.org: Documentation/vm/transhuge.txt too]
[sfr@canb.auug.org.au: sync ethernet driver changes]
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Sunil Goutham <sgoutham@cavium.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Manish Chopra <manish.chopra@qlogic.com>
Cc: Yuval Mintz <yuval.mintz@qlogic.com>
Cc: Tariq Toukan <tariqt@mellanox.com>
Cc: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/vm')
| -rw-r--r-- | Documentation/vm/transhuge.txt | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/Documentation/vm/transhuge.txt b/Documentation/vm/transhuge.txt index d9cb65cf5cfd..fb0e1f2a19cc 100644 --- a/Documentation/vm/transhuge.txt +++ b/Documentation/vm/transhuge.txt @@ -394,9 +394,9 @@ hugepage natively. Once finished you can drop the page table lock. Refcounting on THP is mostly consistent with refcounting on other compound pages: - - get_page()/put_page() and GUP operate in head page's ->_count. + - get_page()/put_page() and GUP operate in head page's ->_refcount. - - ->_count in tail pages is always zero: get_page_unless_zero() never + - ->_refcount in tail pages is always zero: get_page_unless_zero() never succeed on tail pages. - map/unmap of the pages with PTE entry increment/decrement ->_mapcount @@ -426,15 +426,15 @@ requests to split pinned huge page: it expects page count to be equal to sum of mapcount of all sub-pages plus one (split_huge_page caller must have reference for head page). -split_huge_page uses migration entries to stabilize page->_count and +split_huge_page uses migration entries to stabilize page->_refcount and page->_mapcount. We safe against physical memory scanners too: the only legitimate way scanner can get reference to a page is get_page_unless_zero(). -All tail pages has zero ->_count until atomic_add(). It prevent scanner +All tail pages has zero ->_refcount until atomic_add(). It prevent scanner from geting reference to tail page up to the point. After the atomic_add() -we don't care about ->_count value. We already known how many references +we don't care about ->_refcount value. We already known how many references with should uncharge from head page. For head page get_page_unless_zero() will succeed and we don't mind. It's |