mm: Add memalloc_nowait

Similar to memalloc_noio() and memalloc_nofs(), memalloc_nowait()
guarantees we will not sleep to reclaim memory.  Use it to simplify
dm-bufio's allocations.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index 6d1565021d74ccbe795d2e0338f5a8f8b15fb558..140ada9a2c8f71d48267d2f3cb99a73cb355166b 100644 (file)
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -412,23 +412,6 @@ static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,
 
        *data_mode = DATA_MODE_VMALLOC;
 
-       /*
-        * __vmalloc allocates the data pages and auxiliary structures with
-        * gfp_flags that were specified, but pagetables are always allocated
-        * with GFP_KERNEL, no matter what was specified as gfp_mask.
-        *
-        * Consequently, we must set per-process flag PF_MEMALLOC_NOIO so that
-        * all allocations done by this process (including pagetables) are done
-        * as if GFP_NOIO was specified.
-        */
-       if (gfp_mask & __GFP_NORETRY) {
-               unsigned noio_flag = memalloc_noio_save();
-               void *ptr = __vmalloc(c->block_size, gfp_mask);
-
-               memalloc_noio_restore(noio_flag);
-               return ptr;
-       }
-
        return __vmalloc(c->block_size, gfp_mask);
 }
 
@@ -866,9 +849,6 @@ static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client
         * dm-bufio is resistant to allocation failures (it just keeps
         * one buffer reserved in cases all the allocations fail).
         * So set flags to not try too hard:
-        *      GFP_NOWAIT: don't wait; if we need to sleep we'll release our
-        *                  mutex and wait ourselves.
-        *      __GFP_NORETRY: don't retry and rather return failure
         *      __GFP_NOMEMALLOC: don't use emergency reserves
         *      __GFP_NOWARN: don't print a warning in case of failure
         *
@@ -877,7 +857,9 @@ static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client
         */
        while (1) {
                if (dm_bufio_cache_size_latch != 1) {
-                       b = alloc_buffer(c, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
+                       unsigned nowait_flag = memalloc_nowait_save();
+                       b = alloc_buffer(c, GFP_KERNEL | __GFP_NOMEMALLOC | __GFP_NOWARN);
+                       memalloc_nowait_restore(nowait_flag);
                        if (b)
                                return b;
                }
@@ -886,8 +868,12 @@ static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client
                        return NULL;
 
                if (dm_bufio_cache_size_latch != 1 && !tried_noio_alloc) {
+                       unsigned noio_flag;
+
                        dm_bufio_unlock(c);
-                       b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
+                       noio_flag = memalloc_noio_save();
+                       b = alloc_buffer(c, GFP_KERNEL | __GFP_NOMEMALLOC | __GFP_NOWARN);
+                       memalloc_noio_restore(noio_flag);
                        dm_bufio_lock(c);
                        if (b)
                                return b;

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 90336850e9401e53c1872a12e935382626551daf..b1c2cddd366c66f4b0a401251ee1bdd8e93bb5c4 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -803,6 +803,7 @@ struct task_struct {
 #endif
        unsigned                        memalloc_noio:1;
        unsigned                        memalloc_nofs:1;
+       unsigned                        memalloc_nowait:1;
        unsigned                        memalloc_nocma:1;
 
        unsigned long                   atomic_flags; /* Flags requiring atomic access. */

diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index 6f7b59a848a6932a31c380682c48f789aa530a18..6484569f50df928984d83b3b2946aa118af7f615 100644 (file)
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -179,12 +179,16 @@ static inline bool in_vfork(struct task_struct *tsk)
 static inline gfp_t current_gfp_context(gfp_t flags)
 {
        if (unlikely(current->memalloc_noio || current->memalloc_nofs ||
-                    current->memalloc_nocma)) {
+                    current->memalloc_nocma) || current->memalloc_nowait) {
                /*
-                * NOIO implies both NOIO and NOFS and it is a weaker context
-                * so always make sure it makes precedence
+                * Clearing DIRECT_RECLAIM means we won't get to the point
+                * of testing IO or FS, so we don't need to bother clearing
+                * them.  noio implies neither IO nor FS and it is a weaker
+                * context so always make sure it takes precedence.
                 */
-               if (current->memalloc_noio)
+               if (current->memalloc_nowait)
+                       flags &= ~__GFP_DIRECT_RECLAIM;
+               else if (current->memalloc_noio)
                        flags &= ~(__GFP_IO | __GFP_FS);
                else if (current->memalloc_nofs)
                        flags &= ~__GFP_FS;