lib/genalloc: introduce chunk owners

The p2pdma facility enables a provider to publish a pool of dma
addresses for a consumer to allocate.  A genpool is used internally by
p2pdma to collect dma resources, 'chunks', to be handed out to
consumers.  Whenever a consumer allocates a resource it needs to pin the
'struct dev_pagemap' instance that backs the chunk selected by
pci_alloc_p2pmem().

Currently that reference is taken globally on the entire provider
device.  That sets up a lifetime mismatch whereby the p2pdma core needs
to maintain hacks to make sure the percpu_ref is not released twice.

This lifetime mismatch also stands in the way of a fix to
devm_memremap_pages() whereby devm_memremap_pages_release() must wait for
the percpu_ref ->release() callback to complete before it can proceed to
teardown pages.

So, towards fixing this situation, introduce the ability to store a 'chunk
owner' at gen_pool_add() time, and a facility to retrieve the owner at
gen_pool_{alloc,free}() time.  For p2pdma this will be used to store and
recall individual dev_pagemap reference counter instances per-chunk.

Link: http://lkml.kernel.org/r/155727338118.292046.13407378933221579644.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 74 insertions, 32 deletions

diff --git a/include/linux/genalloc.h b/include/linux/genalloc.h
index dd0a452373e7..a337313e064f 100644
--- a/include/linux/genalloc.h
+++ b/include/linux/genalloc.h
@@ -75,6 +75,7 @@ struct gen_pool_chunk {
         struct list_head next_chunk;    /* next chunk in pool */
         atomic_long_t avail;
         phys_addr_t phys_addr;          /* physical starting address of memory chunk */
+        void *owner;                    /* private data to retrieve at alloc time */
         unsigned long start_addr;       /* start address of memory chunk */
         unsigned long end_addr;         /* end address of memory chunk (inclusive) */
         unsigned long bits[0];          /* bitmap for allocating memory chunk */
@@ -96,8 +97,15 @@ struct genpool_data_fixed {
 
 extern struct gen_pool *gen_pool_create(int, int);
 extern phys_addr_t gen_pool_virt_to_phys(struct gen_pool *pool, unsigned long);
-extern int gen_pool_add_virt(struct gen_pool *, unsigned long, phys_addr_t,
-                             size_t, int);
+extern int gen_pool_add_owner(struct gen_pool *, unsigned long, phys_addr_t,
+                             size_t, int, void *);
+
+static inline int gen_pool_add_virt(struct gen_pool *pool, unsigned long addr,
+                phys_addr_t phys, size_t size, int nid)
+{
+        return gen_pool_add_owner(pool, addr, phys, size, nid, NULL);
+}
+
 /**
  * gen_pool_add - add a new chunk of special memory to the pool
  * @pool: pool to add new memory chunk to
@@ -116,12 +124,47 @@ static inline int gen_pool_add(struct gen_pool *pool, unsigned long addr,
         return gen_pool_add_virt(pool, addr, -1, size, nid);
 }
 extern void gen_pool_destroy(struct gen_pool *);
-extern unsigned long gen_pool_alloc(struct gen_pool *, size_t);
-extern unsigned long gen_pool_alloc_algo(struct gen_pool *, size_t,
-                genpool_algo_t algo, void *data);
+unsigned long gen_pool_alloc_algo_owner(struct gen_pool *pool, size_t size,
+                genpool_algo_t algo, void *data, void **owner);
+
+static inline unsigned long gen_pool_alloc_owner(struct gen_pool *pool,
+                size_t size, void **owner)
+{
+        return gen_pool_alloc_algo_owner(pool, size, pool->algo, pool->data,
+                        owner);
+}
+
+static inline unsigned long gen_pool_alloc_algo(struct gen_pool *pool,
+                size_t size, genpool_algo_t algo, void *data)
+{
+        return gen_pool_alloc_algo_owner(pool, size, algo, data, NULL);
+}
+
+/**
+ * gen_pool_alloc - allocate special memory from the pool
+ * @pool: pool to allocate from
+ * @size: number of bytes to allocate from the pool
+ *
+ * Allocate the requested number of bytes from the specified pool.
+ * Uses the pool allocation function (with first-fit algorithm by default).
+ * Can not be used in NMI handler on architectures without
+ * NMI-safe cmpxchg implementation.
+ */
+static inline unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
+{
+        return gen_pool_alloc_algo(pool, size, pool->algo, pool->data);
+}
+
 extern void *gen_pool_dma_alloc(struct gen_pool *pool, size_t size,
                 dma_addr_t *dma);
-extern void gen_pool_free(struct gen_pool *, unsigned long, size_t);
+extern void gen_pool_free_owner(struct gen_pool *pool, unsigned long addr,
+                size_t size, void **owner);
+static inline void gen_pool_free(struct gen_pool *pool, unsigned long addr,
+                size_t size)
+{
+        gen_pool_free_owner(pool, addr, size, NULL);
+}
+
 extern void gen_pool_for_each_chunk(struct gen_pool *,
         void (*)(struct gen_pool *, struct gen_pool_chunk *, void *), void *);
 extern size_t gen_pool_avail(struct gen_pool *);
diff --git a/lib/genalloc.c b/lib/genalloc.c
index 7e85d1e37a6e..770c769d7cb7 100644
--- a/lib/genalloc.c
+++ b/lib/genalloc.c
@@ -168,20 +168,21 @@ struct gen_pool *gen_pool_create(int min_alloc_order, int nid)
 EXPORT_SYMBOL(gen_pool_create);
 
 /**
- * gen_pool_add_virt - add a new chunk of special memory to the pool
+ * gen_pool_add_owner- add a new chunk of special memory to the pool
  * @pool: pool to add new memory chunk to
  * @virt: virtual starting address of memory chunk to add to pool
  * @phys: physical starting address of memory chunk to add to pool
  * @size: size in bytes of the memory chunk to add to pool
  * @nid: node id of the node the chunk structure and bitmap should be
  *       allocated on, or -1
+ * @owner: private data the publisher would like to recall at alloc time
  *
  * Add a new chunk of special memory to the specified pool.
  *
  * Returns 0 on success or a -ve errno on failure.
  */
-int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phys,
-                 size_t size, int nid)
+int gen_pool_add_owner(struct gen_pool *pool, unsigned long virt, phys_addr_t phys,
+                 size_t size, int nid, void *owner)
 {
         struct gen_pool_chunk *chunk;
         int nbits = size >> pool->min_alloc_order;
@@ -195,6 +196,7 @@ int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phy
         chunk->phys_addr = phys;
         chunk->start_addr = virt;
         chunk->end_addr = virt + size - 1;
+        chunk->owner = owner;
         atomic_long_set(&chunk->avail, size);
 
         spin_lock(&pool->lock);
@@ -203,7 +205,7 @@ int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phy
 
         return 0;
 }
-EXPORT_SYMBOL(gen_pool_add_virt);
+EXPORT_SYMBOL(gen_pool_add_owner);
 
 /**
  * gen_pool_virt_to_phys - return the physical address of memory
@@ -260,35 +262,20 @@ void gen_pool_destroy(struct gen_pool *pool)
 EXPORT_SYMBOL(gen_pool_destroy);
 
 /**
- * gen_pool_alloc - allocate special memory from the pool
- * @pool: pool to allocate from
- * @size: number of bytes to allocate from the pool
- *
- * Allocate the requested number of bytes from the specified pool.
- * Uses the pool allocation function (with first-fit algorithm by default).
- * Can not be used in NMI handler on architectures without
- * NMI-safe cmpxchg implementation.
- */
-unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
-{
-        return gen_pool_alloc_algo(pool, size, pool->algo, pool->data);
-}
-EXPORT_SYMBOL(gen_pool_alloc);
-
-/**
- * gen_pool_alloc_algo - allocate special memory from the pool
+ * gen_pool_alloc_algo_owner - allocate special memory from the pool
  * @pool: pool to allocate from
  * @size: number of bytes to allocate from the pool
  * @algo: algorithm passed from caller
  * @data: data passed to algorithm
+ * @owner: optionally retrieve the chunk owner
  *
  * Allocate the requested number of bytes from the specified pool.
  * Uses the pool allocation function (with first-fit algorithm by default).
  * Can not be used in NMI handler on architectures without
  * NMI-safe cmpxchg implementation.
  */
-unsigned long gen_pool_alloc_algo(struct gen_pool *pool, size_t size,
-                genpool_algo_t algo, void *data)
+unsigned long gen_pool_alloc_algo_owner(struct gen_pool *pool, size_t size,
+                genpool_algo_t algo, void *data, void **owner)
 {
         struct gen_pool_chunk *chunk;
         unsigned long addr = 0;
@@ -299,6 +286,9 @@ unsigned long gen_pool_alloc_algo(struct gen_pool *pool, size_t size,
         BUG_ON(in_nmi());
 #endif
 
+        if (owner)
+                *owner = NULL;
+
         if (size == 0)
                 return 0;
 
@@ -326,12 +316,14 @@ retry:
                 addr = chunk->start_addr + ((unsigned long)start_bit << order);
                 size = nbits << order;
                 atomic_long_sub(size, &chunk->avail);
+                if (owner)
+                        *owner = chunk->owner;
                 break;
         }
         rcu_read_unlock();
         return addr;
 }
-EXPORT_SYMBOL(gen_pool_alloc_algo);
+EXPORT_SYMBOL(gen_pool_alloc_algo_owner);
 
 /**
  * gen_pool_dma_alloc - allocate special memory from the pool for DMA usage
@@ -367,12 +359,14 @@ EXPORT_SYMBOL(gen_pool_dma_alloc);
  * @pool: pool to free to
  * @addr: starting address of memory to free back to pool
  * @size: size in bytes of memory to free
+ * @owner: private data stashed at gen_pool_add() time
  *
  * Free previously allocated special memory back to the specified
  * pool.  Can not be used in NMI handler on architectures without
  * NMI-safe cmpxchg implementation.
  */
-void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
+void gen_pool_free_owner(struct gen_pool *pool, unsigned long addr, size_t size,
+                void **owner)
 {
         struct gen_pool_chunk *chunk;
         int order = pool->min_alloc_order;
@@ -382,6 +376,9 @@ void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
         BUG_ON(in_nmi());
 #endif
 
+        if (owner)
+                *owner = NULL;
+
         nbits = (size + (1UL << order) - 1) >> order;
         rcu_read_lock();
         list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
@@ -392,6 +389,8 @@ void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
                         BUG_ON(remain);
                         size = nbits << order;
                         atomic_long_add(size, &chunk->avail);
+                        if (owner)
+                                *owner = chunk->owner;
                         rcu_read_unlock();
                         return;
                 }
@@ -399,7 +398,7 @@ void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
         rcu_read_unlock();
         BUG();
 }
-EXPORT_SYMBOL(gen_pool_free);
+EXPORT_SYMBOL(gen_pool_free_owner);
 
 /**
  * gen_pool_for_each_chunk - call func for every chunk of generic memory pool