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>
diff --git a/Documentation/vm/transhuge.txt b/Documentation/vm/transhuge.txt
index d9cb65c..fb0e1f2 100644
--- a/Documentation/vm/transhuge.txt
+++ b/Documentation/vm/transhuge.txt
@@ -394,9 +394,9 @@
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 @@
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
diff --git a/arch/tile/mm/init.c b/arch/tile/mm/init.c
index a0582b7..adce254 100644
--- a/arch/tile/mm/init.c
+++ b/arch/tile/mm/init.c
@@ -679,7 +679,7 @@
* Hacky direct set to avoid unnecessary
* lock take/release for EVERY page here.
*/
- p->_count.counter = 0;
+ p->_refcount.counter = 0;
p->_mapcount.counter = -1;
}
init_page_count(page);
diff --git a/drivers/block/aoe/aoecmd.c b/drivers/block/aoe/aoecmd.c
index 437b3a8..d597e43 100644
--- a/drivers/block/aoe/aoecmd.c
+++ b/drivers/block/aoe/aoecmd.c
@@ -861,7 +861,7 @@
* discussion.
*
* We cannot use get_page in the workaround, because it insists on a
- * positive page count as a precondition. So we use _count directly.
+ * positive page count as a precondition. So we use _refcount directly.
*/
static void
bio_pageinc(struct bio *bio)
diff --git a/drivers/hwtracing/intel_th/msu.c b/drivers/hwtracing/intel_th/msu.c
index d9d6022..d220914 100644
--- a/drivers/hwtracing/intel_th/msu.c
+++ b/drivers/hwtracing/intel_th/msu.c
@@ -1164,7 +1164,7 @@
if (!atomic_dec_and_mutex_lock(&msc->mmap_count, &msc->buf_mutex))
return;
- /* drop page _counts */
+ /* drop page _refcounts */
for (pg = 0; pg < msc->nr_pages; pg++) {
struct page *page = msc_buffer_get_page(msc, pg);
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
index f345679..bd94770 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
@@ -433,8 +433,8 @@
for (i = 0; i < MLX5_MPWRQ_PAGES_PER_WQE; i++) {
if (unlikely(mlx5e_alloc_and_map_page(rq, wi, i)))
goto err_unmap;
- atomic_add(mlx5e_mpwqe_strides_per_page(rq),
- &wi->umr.dma_info[i].page->_count);
+ page_ref_add(wi->umr.dma_info[i].page,
+ mlx5e_mpwqe_strides_per_page(rq));
wi->skbs_frags[i] = 0;
}
@@ -452,8 +452,8 @@
while (--i >= 0) {
dma_unmap_page(rq->pdev, wi->umr.dma_info[i].addr, PAGE_SIZE,
PCI_DMA_FROMDEVICE);
- atomic_sub(mlx5e_mpwqe_strides_per_page(rq),
- &wi->umr.dma_info[i].page->_count);
+ page_ref_sub(wi->umr.dma_info[i].page,
+ mlx5e_mpwqe_strides_per_page(rq));
put_page(wi->umr.dma_info[i].page);
}
dma_unmap_single(rq->pdev, wi->umr.mtt_addr, mtt_sz, PCI_DMA_TODEVICE);
@@ -477,8 +477,8 @@
for (i = 0; i < MLX5_MPWRQ_PAGES_PER_WQE; i++) {
dma_unmap_page(rq->pdev, wi->umr.dma_info[i].addr, PAGE_SIZE,
PCI_DMA_FROMDEVICE);
- atomic_sub(mlx5e_mpwqe_strides_per_page(rq) - wi->skbs_frags[i],
- &wi->umr.dma_info[i].page->_count);
+ page_ref_sub(wi->umr.dma_info[i].page,
+ mlx5e_mpwqe_strides_per_page(rq) - wi->skbs_frags[i]);
put_page(wi->umr.dma_info[i].page);
}
dma_unmap_single(rq->pdev, wi->umr.mtt_addr, mtt_sz, PCI_DMA_TODEVICE);
@@ -527,8 +527,8 @@
*/
split_page(wi->dma_info.page, MLX5_MPWRQ_WQE_PAGE_ORDER);
for (i = 0; i < MLX5_MPWRQ_PAGES_PER_WQE; i++) {
- atomic_add(mlx5e_mpwqe_strides_per_page(rq),
- &wi->dma_info.page[i]._count);
+ page_ref_add(&wi->dma_info.page[i],
+ mlx5e_mpwqe_strides_per_page(rq));
wi->skbs_frags[i] = 0;
}
@@ -551,8 +551,8 @@
dma_unmap_page(rq->pdev, wi->dma_info.addr, rq->wqe_sz,
PCI_DMA_FROMDEVICE);
for (i = 0; i < MLX5_MPWRQ_PAGES_PER_WQE; i++) {
- atomic_sub(mlx5e_mpwqe_strides_per_page(rq) - wi->skbs_frags[i],
- &wi->dma_info.page[i]._count);
+ page_ref_sub(&wi->dma_info.page[i],
+ mlx5e_mpwqe_strides_per_page(rq) - wi->skbs_frags[i]);
put_page(&wi->dma_info.page[i]);
}
}
diff --git a/drivers/net/ethernet/qlogic/qede/qede_main.c b/drivers/net/ethernet/qlogic/qede/qede_main.c
index 3aabfc0..73dd525 100644
--- a/drivers/net/ethernet/qlogic/qede/qede_main.c
+++ b/drivers/net/ethernet/qlogic/qede/qede_main.c
@@ -1036,7 +1036,7 @@
/* Incr page ref count to reuse on allocation failure
* so that it doesn't get freed while freeing SKB.
*/
- atomic_inc(¤t_bd->data->_count);
+ page_ref_inc(current_bd->data);
goto out;
}
@@ -1487,7 +1487,7 @@
* freeing SKB.
*/
- atomic_inc(&sw_rx_data->data->_count);
+ page_ref_inc(sw_rx_data->data);
rxq->rx_alloc_errors++;
qede_recycle_rx_bd_ring(rxq, edev,
fp_cqe->bd_num);
diff --git a/fs/proc/page.c b/fs/proc/page.c
index 712f1b9..3ecd445 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -142,7 +142,7 @@
/*
- * Caveats on high order pages: page->_count will only be set
+ * Caveats on high order pages: page->_refcount will only be set
* -1 on the head page; SLUB/SLQB do the same for PG_slab;
* SLOB won't set PG_slab at all on compound pages.
*/
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 727f7997..1193a54 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -734,7 +734,7 @@
page = compound_head(page);
/*
* Getting a normal page or the head of a compound page
- * requires to already have an elevated page->_count.
+ * requires to already have an elevated page->_refcount.
*/
VM_BUG_ON_PAGE(page_ref_count(page) <= 0, page);
page_ref_inc(page);
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index c2d75b4..1fda9c99 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -73,9 +73,9 @@
unsigned long counters;
#else
/*
- * Keep _count separate from slub cmpxchg_double data.
- * As the rest of the double word is protected by
- * slab_lock but _count is not.
+ * Keep _refcount separate from slub cmpxchg_double
+ * data. As the rest of the double word is protected by
+ * slab_lock but _refcount is not.
*/
unsigned counters;
#endif
@@ -97,7 +97,11 @@
};
int units; /* SLOB */
};
- atomic_t _count; /* Usage count, see below. */
+ /*
+ * Usage count, *USE WRAPPER FUNCTION*
+ * when manual accounting. See page_ref.h
+ */
+ atomic_t _refcount;
};
unsigned int active; /* SLAB */
};
@@ -248,7 +252,7 @@
__u32 offset;
#endif
/* we maintain a pagecount bias, so that we dont dirty cache line
- * containing page->_count every time we allocate a fragment.
+ * containing page->_refcount every time we allocate a fragment.
*/
unsigned int pagecnt_bias;
bool pfmemalloc;
diff --git a/include/linux/page_ref.h b/include/linux/page_ref.h
index e596d5d9..8b5e0a9 100644
--- a/include/linux/page_ref.h
+++ b/include/linux/page_ref.h
@@ -63,17 +63,17 @@
static inline int page_ref_count(struct page *page)
{
- return atomic_read(&page->_count);
+ return atomic_read(&page->_refcount);
}
static inline int page_count(struct page *page)
{
- return atomic_read(&compound_head(page)->_count);
+ return atomic_read(&compound_head(page)->_refcount);
}
static inline void set_page_count(struct page *page, int v)
{
- atomic_set(&page->_count, v);
+ atomic_set(&page->_refcount, v);
if (page_ref_tracepoint_active(__tracepoint_page_ref_set))
__page_ref_set(page, v);
}
@@ -89,35 +89,35 @@
static inline void page_ref_add(struct page *page, int nr)
{
- atomic_add(nr, &page->_count);
+ atomic_add(nr, &page->_refcount);
if (page_ref_tracepoint_active(__tracepoint_page_ref_mod))
__page_ref_mod(page, nr);
}
static inline void page_ref_sub(struct page *page, int nr)
{
- atomic_sub(nr, &page->_count);
+ atomic_sub(nr, &page->_refcount);
if (page_ref_tracepoint_active(__tracepoint_page_ref_mod))
__page_ref_mod(page, -nr);
}
static inline void page_ref_inc(struct page *page)
{
- atomic_inc(&page->_count);
+ atomic_inc(&page->_refcount);
if (page_ref_tracepoint_active(__tracepoint_page_ref_mod))
__page_ref_mod(page, 1);
}
static inline void page_ref_dec(struct page *page)
{
- atomic_dec(&page->_count);
+ atomic_dec(&page->_refcount);
if (page_ref_tracepoint_active(__tracepoint_page_ref_mod))
__page_ref_mod(page, -1);
}
static inline int page_ref_sub_and_test(struct page *page, int nr)
{
- int ret = atomic_sub_and_test(nr, &page->_count);
+ int ret = atomic_sub_and_test(nr, &page->_refcount);
if (page_ref_tracepoint_active(__tracepoint_page_ref_mod_and_test))
__page_ref_mod_and_test(page, -nr, ret);
@@ -126,7 +126,7 @@
static inline int page_ref_dec_and_test(struct page *page)
{
- int ret = atomic_dec_and_test(&page->_count);
+ int ret = atomic_dec_and_test(&page->_refcount);
if (page_ref_tracepoint_active(__tracepoint_page_ref_mod_and_test))
__page_ref_mod_and_test(page, -1, ret);
@@ -135,7 +135,7 @@
static inline int page_ref_dec_return(struct page *page)
{
- int ret = atomic_dec_return(&page->_count);
+ int ret = atomic_dec_return(&page->_refcount);
if (page_ref_tracepoint_active(__tracepoint_page_ref_mod_and_return))
__page_ref_mod_and_return(page, -1, ret);
@@ -144,7 +144,7 @@
static inline int page_ref_add_unless(struct page *page, int nr, int u)
{
- int ret = atomic_add_unless(&page->_count, nr, u);
+ int ret = atomic_add_unless(&page->_refcount, nr, u);
if (page_ref_tracepoint_active(__tracepoint_page_ref_mod_unless))
__page_ref_mod_unless(page, nr, ret);
@@ -153,7 +153,7 @@
static inline int page_ref_freeze(struct page *page, int count)
{
- int ret = likely(atomic_cmpxchg(&page->_count, count, 0) == count);
+ int ret = likely(atomic_cmpxchg(&page->_refcount, count, 0) == count);
if (page_ref_tracepoint_active(__tracepoint_page_ref_freeze))
__page_ref_freeze(page, count, ret);
@@ -165,7 +165,7 @@
VM_BUG_ON_PAGE(page_count(page) != 0, page);
VM_BUG_ON(count == 0);
- atomic_set(&page->_count, count);
+ atomic_set(&page->_refcount, count);
if (page_ref_tracepoint_active(__tracepoint_page_ref_unfreeze))
__page_ref_unfreeze(page, count);
}
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 7e1ab15..fe1513f 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -90,12 +90,12 @@
/*
* speculatively take a reference to a page.
- * If the page is free (_count == 0), then _count is untouched, and 0
- * is returned. Otherwise, _count is incremented by 1 and 1 is returned.
+ * If the page is free (_refcount == 0), then _refcount is untouched, and 0
+ * is returned. Otherwise, _refcount is incremented by 1 and 1 is returned.
*
* This function must be called inside the same rcu_read_lock() section as has
* been used to lookup the page in the pagecache radix-tree (or page table):
- * this allows allocators to use a synchronize_rcu() to stabilize _count.
+ * this allows allocators to use a synchronize_rcu() to stabilize _refcount.
*
* Unless an RCU grace period has passed, the count of all pages coming out
* of the allocator must be considered unstable. page_count may return higher
@@ -111,7 +111,7 @@
* 2. conditionally increment refcount
* 3. check the page is still in pagecache (if no, goto 1)
*
- * Remove-side that cares about stability of _count (eg. reclaim) has the
+ * Remove-side that cares about stability of _refcount (eg. reclaim) has the
* following (with tree_lock held for write):
* A. atomically check refcount is correct and set it to 0 (atomic_cmpxchg)
* B. remove page from pagecache
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 1391d3e..1c03dfb 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -1410,7 +1410,7 @@
VMCOREINFO_STRUCT_SIZE(list_head);
VMCOREINFO_SIZE(nodemask_t);
VMCOREINFO_OFFSET(page, flags);
- VMCOREINFO_OFFSET(page, _count);
+ VMCOREINFO_OFFSET(page, _refcount);
VMCOREINFO_OFFSET(page, mapping);
VMCOREINFO_OFFSET(page, lru);
VMCOREINFO_OFFSET(page, _mapcount);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index b49ee126..f8ac8f5 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3113,7 +3113,7 @@
VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail);
/*
- * tail_page->_count is zero and not changing from under us. But
+ * tail_page->_refcount is zero and not changing from under us. But
* get_page_unless_zero() may be running from under us on the
* tail_page. If we used atomic_set() below instead of atomic_inc(), we
* would then run atomic_set() concurrently with
@@ -3340,7 +3340,7 @@
if (mlocked)
lru_add_drain();
- /* Prevent deferred_split_scan() touching ->_count */
+ /* Prevent deferred_split_scan() touching ->_refcount */
spin_lock_irqsave(&pgdata->split_queue_lock, flags);
count = page_count(head);
mapcount = total_mapcount(head);
diff --git a/mm/internal.h b/mm/internal.h
index b79abb6..098a89e 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -58,7 +58,7 @@
}
/*
- * Turn a non-refcounted page (->_count == 0) into refcounted with
+ * Turn a non-refcounted page (->_refcount == 0) into refcounted with
* a count of one.
*/
static inline void set_page_refcounted(struct page *page)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c1069ef..4ce57f9 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -794,7 +794,7 @@
if (unlikely(page->mapping != NULL))
bad_reason = "non-NULL mapping";
if (unlikely(page_ref_count(page) != 0))
- bad_reason = "nonzero _count";
+ bad_reason = "nonzero _refcount";
if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_FREE)) {
bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set";
bad_flags = PAGE_FLAGS_CHECK_AT_FREE;
@@ -6864,7 +6864,7 @@
* We can't use page_count without pin a page
* because another CPU can free compound page.
* This check already skips compound tails of THP
- * because their page->_count is zero at all time.
+ * because their page->_refcount is zero at all time.
*/
if (!page_ref_count(page)) {
if (PageBuddy(page))
diff --git a/mm/slub.c b/mm/slub.c
index 8671de2..cf1faa4 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -329,8 +329,8 @@
tmp.counters = counters_new;
/*
* page->counters can cover frozen/inuse/objects as well
- * as page->_count. If we assign to ->counters directly
- * we run the risk of losing updates to page->_count, so
+ * as page->_refcount. If we assign to ->counters directly
+ * we run the risk of losing updates to page->_refcount, so
* be careful and only assign to the fields we need.
*/
page->frozen = tmp.frozen;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 142cb61..d3a02ac 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -633,7 +633,7 @@
*
* Reversing the order of the tests ensures such a situation cannot
* escape unnoticed. The smp_rmb is needed to ensure the page->flags
- * load is not satisfied before that of page->_count.
+ * load is not satisfied before that of page->_refcount.
*
* Note that if SetPageDirty is always performed via set_page_dirty,
* and thus under tree_lock, then this ordering is not required.
@@ -1720,7 +1720,7 @@
* It is safe to rely on PG_active against the non-LRU pages in here because
* nobody will play with that bit on a non-LRU page.
*
- * The downside is that we have to touch page->_count against each page.
+ * The downside is that we have to touch page->_refcount against each page.
* But we had to alter page->flags anyway.
*/