[PATCH 09/10] mm: Rename PG_mappedtodisk to PG_owner_2

Matthew Wilcox (Oracle)
2024-08-21T19:34:53Z

This flag has similar constraints to PG_owner_priv_1 -- it is ignored
by core code, and is entirely for the use of the code which allocated
the folio. Since the pagecache does not use it, individual filesystems
can use it. The bufferhead code does use it, so filesystems which use
the buffer cache must not use it for another purpose.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
fs/proc/page.c | 2 +-
include/linux/kernel-page-flags.h | 2 +-
include/linux/page-flags.h | 24 ++++++++++++++++--------
include/trace/events/mmflags.h | 2 +-
tools/mm/page-types.c | 10 +++++-----
5 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/fs/proc/page.c b/fs/proc/page.c
index 73a0f872d97f..e74e639893be 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -211,7 +211,7 @@ u64 stable_page_flags(const struct page *page)
#endif

u |= kpf_copy_bit(k, KPF_RESERVED, PG_reserved);
- u |= kpf_copy_bit(k, KPF_MAPPEDTODISK, PG_mappedtodisk);
+ u |= kpf_copy_bit(k, KPF_OWNER_2, PG_owner_2);
u |= kpf_copy_bit(k, KPF_PRIVATE, PG_private);
u |= kpf_copy_bit(k, KPF_PRIVATE_2, PG_private_2);
u |= kpf_copy_bit(k, KPF_OWNER_PRIVATE, PG_owner_priv_1);
diff --git a/include/linux/kernel-page-flags.h b/include/linux/kernel-page-flags.h
index 859f4b0c1b2b..7c587a711be1 100644
--- a/include/linux/kernel-page-flags.h
+++ b/include/linux/kernel-page-flags.h
@@ -10,7 +10,7 @@
*/
#define KPF_RESERVED 32
#define KPF_MLOCKED 33
-#define KPF_MAPPEDTODISK 34
+#define KPF_OWNER_2 34
#define KPF_PRIVATE 35
#define KPF_PRIVATE_2 36
#define KPF_OWNER_PRIVATE 37
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 3513aa666c31..c001e3c29c4c 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -101,12 +101,12 @@ enum pageflags {
PG_waiters, /* Page has waiters, check its waitqueue. Must be bit #7 and in the same byte as "PG_locked" */
PG_active,
PG_workingset,
- PG_owner_priv_1, /* Owner use. If pagecache, fs may use*/
+ PG_owner_priv_1, /* Owner use. If pagecache, fs may use */
+ PG_owner_2, /* Owner use. If pagecache, fs may use */
PG_arch_1,
PG_reserved,
PG_private, /* If pagecache, has fs-private data */
PG_private_2, /* If pagecache, has fs aux data */
- PG_mappedtodisk, /* Has blocks allocated on-disk */
PG_reclaim, /* To be reclaimed asap */
PG_swapbacked, /* Page is backed by RAM/swap */
PG_unevictable, /* Page is "unevictable" */
@@ -131,6 +131,11 @@ enum pageflags {

PG_readahead = PG_reclaim,

+ /* Anonymous memory (and shmem) */
+ PG_swapcache = PG_owner_priv_1, /* Swap page: swp_entry_t in private */
+ /* Some filesystems */
+ PG_checked = PG_owner_priv_1,
+
/*
* Depending on the way an anonymous folio can be mapped into a page
* table (e.g., single PMD/PUD/CONT of the head page vs. PTE-mapped
@@ -138,13 +143,13 @@ enum pageflags {
* tail pages of an anonymous folio. For now, we only expect it to be
* set on tail pages for PTE-mapped THP.
*/
- PG_anon_exclusive = PG_mappedtodisk,
-
- /* Filesystems */
- PG_checked = PG_owner_priv_1,
+ PG_anon_exclusive = PG_owner_2,

- /* SwapBacked */
- PG_swapcache = PG_owner_priv_1, /* Swap page: swp_entry_t in private */
+ /*
+ * Set if all buffer heads in the folio are mapped.
+ * Filesystems which do not use BHs can use it for their own purpose.
+ */
+ PG_mappedtodisk = PG_owner_2,

/* Two page bits are conscripted by FS-Cache to maintain local caching
* state. These bits are set on pages belonging to the netfs's inodes
@@ -540,6 +545,9 @@ FOLIO_FLAG(swapbacked, FOLIO_HEAD_PAGE)
PAGEFLAG(Private, private, PF_ANY)
PAGEFLAG(Private2, private_2, PF_ANY) TESTSCFLAG(Private2, private_2, PF_ANY)

+/* owner_2 can be set on tail pages for anon memory */
+FOLIO_FLAG(owner_2, FOLIO_HEAD_PAGE)
+
/*
* Only test-and-set exist for PG_writeback. The unconditional operators are
* risky: they bypass page accounting.
diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
index c151cc21d367..3b51558cdc9b 100644
--- a/include/trace/events/mmflags.h
+++ b/include/trace/events/mmflags.h
@@ -107,13 +107,13 @@
DEF_PAGEFLAG_NAME(active), \
DEF_PAGEFLAG_NAME(workingset), \
DEF_PAGEFLAG_NAME(owner_priv_1), \
+ DEF_PAGEFLAG_NAME(owner_2), \
DEF_PAGEFLAG_NAME(arch_1), \
DEF_PAGEFLAG_NAME(reserved), \
DEF_PAGEFLAG_NAME(private), \
DEF_PAGEFLAG_NAME(private_2), \
DEF_PAGEFLAG_NAME(writeback), \
DEF_PAGEFLAG_NAME(head), \
- DEF_PAGEFLAG_NAME(mappedtodisk), \
DEF_PAGEFLAG_NAME(reclaim), \
DEF_PAGEFLAG_NAME(swapbacked), \
DEF_PAGEFLAG_NAME(unevictable) \
diff --git a/tools/mm/page-types.c b/tools/mm/page-types.c
index 8d5595b6c59f..8ca41c41105e 100644
--- a/tools/mm/page-types.c
+++ b/tools/mm/page-types.c
@@ -71,7 +71,7 @@
/* [32-] kernel hacking assistances */
#define KPF_RESERVED 32
#define KPF_MLOCKED 33
-#define KPF_MAPPEDTODISK 34
+#define KPF_OWNER_2 34
#define KPF_PRIVATE 35
#define KPF_PRIVATE_2 36
#define KPF_OWNER_PRIVATE 37
@@ -129,7 +129,7 @@ static const char * const page_flag_names[] = {

[KPF_RESERVED] = "r:reserved",
[KPF_MLOCKED] = "m:mlocked",
- [KPF_MAPPEDTODISK] = "d:mappedtodisk",
+ [KPF_OWNER_2] = "d:owner_2",
[KPF_PRIVATE] = "P:private",
[KPF_PRIVATE_2] = "p:private_2",
[KPF_OWNER_PRIVATE] = "O:owner_private",
@@ -472,9 +472,9 @@ static int bit_mask_ok(uint64_t flags)

static uint64_t expand_overloaded_flags(uint64_t flags, uint64_t pme)
{
- /* Anonymous pages overload PG_mappedtodisk */
- if ((flags & BIT(ANON)) && (flags & BIT(MAPPEDTODISK)))
- flags ^= BIT(MAPPEDTODISK) | BIT(ANON_EXCLUSIVE);
+ /* Anonymous pages use PG_owner_2 for anon_exclusive */
+ if ((flags & BIT(ANON)) && (flags & BIT(OWNER_2)))
+ flags ^= BIT(OWNER_2) | BIT(ANON_EXCLUSIVE);

/* SLUB overloads several page flags */
if (flags & BIT(SLAB)) {
--
2.43.0