[PATCH 4/6] mm: Replace PF_MEMALLOC_NOFS with memalloc_nofs

Matthew Wilcox (Oracle)
2020-06-25T11:32:29Z

We're short on PF_* flags, so make memalloc_nofs its own bit where we
have plenty of space.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
fs/iomap/buffered-io.c | 2 +-
include/linux/sched.h | 2 +-
include/linux/sched/mm.h | 13 ++++++-------
3 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index bcfc288dba3f..87d66c13bf5c 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -1502,7 +1502,7 @@ iomap_do_writepage(struct page *page, struct writeback_control *wbc, void *data)
* Given that we do not allow direct reclaim to call us, we should
* never be called in a recursive filesystem reclaim context.
*/
- if (WARN_ON_ONCE(current->flags & PF_MEMALLOC_NOFS))
+ if (WARN_ON_ONCE(current->memalloc_nofs))
goto redirty;

/*
diff --git a/include/linux/sched.h b/include/linux/sched.h
index cf18a3d2bc4c..eaf36ae1fde2 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -802,6 +802,7 @@ struct task_struct {
unsigned in_memstall:1;
#endif
unsigned memalloc_noio:1;
+ unsigned memalloc_nofs:1;

unsigned long atomic_flags; /* Flags requiring atomic access. */

@@ -1505,7 +1506,6 @@ extern struct pid *cad_pid;
#define PF_NOFREEZE 0x00008000 /* This thread should not be frozen */
#define PF_FROZEN 0x00010000 /* Frozen for system suspend */
#define PF_KSWAPD 0x00020000 /* I am kswapd */
-#define PF_MEMALLOC_NOFS 0x00040000 /* All allocation requests will inherit GFP_NOFS */
#define PF_LOCAL_THROTTLE 0x00100000 /* Throttle writes only against the bdi I write to,
* I am cleaning dirty pages from some other bdi. */
#define PF_KTHREAD 0x00200000 /* I am a kernel thread */
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index b0089eadc367..08bc9d0606a8 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -175,20 +175,19 @@ static inline bool in_vfork(struct task_struct *tsk)

/*
* Applies per-task gfp context to the given allocation flags.
- * PF_MEMALLOC_NOFS implies GFP_NOFS
* PF_MEMALLOC_NOCMA implies no allocation from CMA region.
*/
static inline gfp_t current_gfp_context(gfp_t flags)
{
- if (unlikely(current->flags & (PF_MEMALLOC_NOFS | PF_MEMALLOC_NOCMA) ||
- current->memalloc_noio)) {
+ if (unlikely((current->flags & PF_MEMALLOC_NOCMA) ||
+ current->memalloc_noio || current->memalloc_nofs)) {
/*
* NOIO implies both NOIO and NOFS and it is a weaker context
* so always make sure it makes precedence
*/
if (current->memalloc_noio)
flags &= ~(__GFP_IO | __GFP_FS);
- else if (current->flags & PF_MEMALLOC_NOFS)
+ else if (current->memalloc_nofs)
flags &= ~__GFP_FS;
#ifdef CONFIG_CMA
if (current->flags & PF_MEMALLOC_NOCMA)
@@ -254,8 +253,8 @@ static inline void memalloc_noio_restore(unsigned int flags)
*/
static inline unsigned int memalloc_nofs_save(void)
{
- unsigned int flags = current->flags & PF_MEMALLOC_NOFS;
- current->flags |= PF_MEMALLOC_NOFS;
+ unsigned int flags = current->memalloc_nofs;
+ current->memalloc_nofs = 1;
return flags;
}

@@ -269,7 +268,7 @@ static inline unsigned int memalloc_nofs_save(void)
*/
static inline void memalloc_nofs_restore(unsigned int flags)
{
- current->flags = (current->flags & ~PF_MEMALLOC_NOFS) | flags;
+ current->memalloc_nofs = flags ? 1 : 0;
}

static inline unsigned int memalloc_noreclaim_save(void)
--
2.27.0