mm: shmem: rename mTHP shmem counters

The legacy PMD-sized THP counters at /proc/vmstat include thp_file_alloc,
thp_file_fallback and thp_file_fallback_charge, which rather confusingly
refer to shmem THP and do not include any other types of file pages.  This
is inconsistent since in most other places in the kernel, THP counters are
explicitly separated for anon, shmem and file flavours.  However, we are
stuck with it since it constitutes a user ABI.

Recently, commit 66f44583f9b6 ("mm: shmem: add mTHP counters for anonymous
shmem") added equivalent mTHP stats for shmem, keeping the same "file_"
prefix in the names.  But in future, we may want to add extra stats to
cover actual file pages, at which point, it would all become very
confusing.

So let's take the opportunity to rename these new counters "shmem_" before
the change makes it upstream and the ABI becomes immutable.  While we are
at it, let's improve the documentation for the legacy counters to make it
clear that they count shmem pages only.

Link: https://lkml.kernel.org/r/20240710095503.3193901-1-ryan.roberts@arm.com
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Lance Yang <ioworker0@gmail.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Daniel Gomez <da.gomez@samsung.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

4 files changed, 29 insertions, 26 deletions

diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index fe237825b95c..058485daf186 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -412,20 +412,23 @@ thp_collapse_alloc_failed
 	the allocation.
 
 thp_file_alloc
-	is incremented every time a file huge page is successfully
-	allocated.
+	is incremented every time a shmem huge page is successfully
+	allocated (Note that despite being named after "file", the counter
+	measures only shmem).
 
 thp_file_fallback
-	is incremented if a file huge page is attempted to be allocated
-	but fails and instead falls back to using small pages.
+	is incremented if a shmem huge page is attempted to be allocated
+	but fails and instead falls back to using small pages. (Note that
+	despite being named after "file", the counter measures only shmem).
 
 thp_file_fallback_charge
-	is incremented if a file huge page cannot be charged and instead
+	is incremented if a shmem huge page cannot be charged and instead
 	falls back to using small pages even though the allocation was
-	successful.
+	successful. (Note that despite being named after "file", the
+	counter measures only shmem).
 
 thp_file_mapped
-	is incremented every time a file huge page is mapped into
+	is incremented every time a file or shmem huge page is mapped into
 	user address space.
 
 thp_split_page
@@ -496,16 +499,16 @@ swpout_fallback
 	Usually because failed to allocate some continuous swap space
 	for the huge page.
 
-file_alloc
-	is incremented every time a file huge page is successfully
+shmem_alloc
+	is incremented every time a shmem huge page is successfully
 	allocated.
 
-file_fallback
-	is incremented if a file huge page is attempted to be allocated
+shmem_fallback
+	is incremented if a shmem huge page is attempted to be allocated
 	but fails and instead falls back to using small pages.
 
-file_fallback_charge
-	is incremented if a file huge page cannot be charged and instead
+shmem_fallback_charge
+	is incremented if a shmem huge page cannot be charged and instead
 	falls back to using small pages even though the allocation was
 	successful.
 
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index acb6ac24a07e..cff002be83eb 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -269,9 +269,9 @@ enum mthp_stat_item {
 	MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE,
 	MTHP_STAT_SWPOUT,
 	MTHP_STAT_SWPOUT_FALLBACK,
-	MTHP_STAT_FILE_ALLOC,
-	MTHP_STAT_FILE_FALLBACK,
-	MTHP_STAT_FILE_FALLBACK_CHARGE,
+	MTHP_STAT_SHMEM_ALLOC,
+	MTHP_STAT_SHMEM_FALLBACK,
+	MTHP_STAT_SHMEM_FALLBACK_CHARGE,
 	MTHP_STAT_SPLIT,
 	MTHP_STAT_SPLIT_FAILED,
 	MTHP_STAT_SPLIT_DEFERRED,
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 9ec64aa2be94..f9696c94e211 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -568,9 +568,9 @@ DEFINE_MTHP_STAT_ATTR(anon_fault_fallback, MTHP_STAT_ANON_FAULT_FALLBACK);
 DEFINE_MTHP_STAT_ATTR(anon_fault_fallback_charge, MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
 DEFINE_MTHP_STAT_ATTR(swpout, MTHP_STAT_SWPOUT);
 DEFINE_MTHP_STAT_ATTR(swpout_fallback, MTHP_STAT_SWPOUT_FALLBACK);
-DEFINE_MTHP_STAT_ATTR(file_alloc, MTHP_STAT_FILE_ALLOC);
-DEFINE_MTHP_STAT_ATTR(file_fallback, MTHP_STAT_FILE_FALLBACK);
-DEFINE_MTHP_STAT_ATTR(file_fallback_charge, MTHP_STAT_FILE_FALLBACK_CHARGE);
+DEFINE_MTHP_STAT_ATTR(shmem_alloc, MTHP_STAT_SHMEM_ALLOC);
+DEFINE_MTHP_STAT_ATTR(shmem_fallback, MTHP_STAT_SHMEM_FALLBACK);
+DEFINE_MTHP_STAT_ATTR(shmem_fallback_charge, MTHP_STAT_SHMEM_FALLBACK_CHARGE);
 DEFINE_MTHP_STAT_ATTR(split, MTHP_STAT_SPLIT);
 DEFINE_MTHP_STAT_ATTR(split_failed, MTHP_STAT_SPLIT_FAILED);
 DEFINE_MTHP_STAT_ATTR(split_deferred, MTHP_STAT_SPLIT_DEFERRED);
@@ -581,9 +581,9 @@ static struct attribute *stats_attrs[] = {
 	&anon_fault_fallback_charge_attr.attr,
 	&swpout_attr.attr,
 	&swpout_fallback_attr.attr,
-	&file_alloc_attr.attr,
-	&file_fallback_attr.attr,
-	&file_fallback_charge_attr.attr,
+	&shmem_alloc_attr.attr,
+	&shmem_fallback_attr.attr,
+	&shmem_fallback_charge_attr.attr,
 	&split_attr.attr,
 	&split_failed_attr.attr,
 	&split_deferred_attr.attr,
diff --git a/mm/shmem.c b/mm/shmem.c
index 921d59c3d669..f24dfbd387ba 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1777,7 +1777,7 @@ static struct folio *shmem_alloc_and_add_folio(struct vm_fault *vmf,
 			if (pages == HPAGE_PMD_NR)
 				count_vm_event(THP_FILE_FALLBACK);
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-			count_mthp_stat(order, MTHP_STAT_FILE_FALLBACK);
+			count_mthp_stat(order, MTHP_STAT_SHMEM_FALLBACK);
 #endif
 			order = next_order(&suitable_orders, order);
 		}
@@ -1804,8 +1804,8 @@ allocated:
 				count_vm_event(THP_FILE_FALLBACK_CHARGE);
 			}
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-			count_mthp_stat(folio_order(folio), MTHP_STAT_FILE_FALLBACK);
-			count_mthp_stat(folio_order(folio), MTHP_STAT_FILE_FALLBACK_CHARGE);
+			count_mthp_stat(folio_order(folio), MTHP_STAT_SHMEM_FALLBACK);
+			count_mthp_stat(folio_order(folio), MTHP_STAT_SHMEM_FALLBACK_CHARGE);
 #endif
 		}
 		goto unlock;
@@ -2181,7 +2181,7 @@ repeat:
 			if (folio_test_pmd_mappable(folio))
 				count_vm_event(THP_FILE_ALLOC);
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-			count_mthp_stat(folio_order(folio), MTHP_STAT_FILE_ALLOC);
+			count_mthp_stat(folio_order(folio), MTHP_STAT_SHMEM_ALLOC);
 #endif
 			goto alloced;
 		}