mm: bdi: add separate writeback accounting capability

Add a new BDI capability flag: BDI_CAP_NO_ACCT_WB.  If this flag is
set, then don't update the per-bdi writeback stats from
test_set_page_writeback() and test_clear_page_writeback().

Misc cleanups:

 - convert bdi_cap_writeback_dirty() and friends to static inline functions
 - create a flag that includes all three dirty/writeback related flags,
   since almst all users will want to have them toghether

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

10 files changed, 67 insertions, 30 deletions

diff --git a/fs/configfs/inode.c b/fs/configfs/inode.c
index 4c1ebff778ee..b9a1d810346d 100644
--- a/fs/configfs/inode.c
+++ b/fs/configfs/inode.c
@@ -47,7 +47,7 @@ static const struct address_space_operations configfs_aops = {
 
 static struct backing_dev_info configfs_backing_dev_info = {
         .ra_pages       = 0,    /* No readahead */
-        .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
+        .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
 };
 
 static const struct inode_operations configfs_inode_operations ={
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 9783723e8ffe..aeabf80f81a5 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -45,7 +45,7 @@ static const struct inode_operations hugetlbfs_inode_operations;
 
 static struct backing_dev_info hugetlbfs_backing_dev_info = {
         .ra_pages       = 0,    /* No readahead */
-        .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
+        .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
 };
 
 int sysctl_hugetlb_shm_group;
diff --git a/fs/ocfs2/dlm/dlmfs.c b/fs/ocfs2/dlm/dlmfs.c
index 61a000f8524c..e48aba698b77 100644
--- a/fs/ocfs2/dlm/dlmfs.c
+++ b/fs/ocfs2/dlm/dlmfs.c
@@ -327,7 +327,7 @@ clear_fields:
 
 static struct backing_dev_info dlmfs_backing_dev_info = {
         .ra_pages       = 0,    /* No readahead */
-        .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
+        .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
 };
 
 static struct inode *dlmfs_get_root_inode(struct super_block *sb)
diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
index 8428d5b2711d..b13123424e49 100644
--- a/fs/ramfs/inode.c
+++ b/fs/ramfs/inode.c
@@ -44,7 +44,7 @@ static const struct inode_operations ramfs_dir_inode_operations;
 
 static struct backing_dev_info ramfs_backing_dev_info = {
         .ra_pages       = 0,    /* No readahead */
-        .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK |
+        .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK |
                           BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY |
                           BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP,
 };
diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index d9262f74f94e..f8b82e73b3bf 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -30,7 +30,7 @@ static const struct address_space_operations sysfs_aops = {
 
 static struct backing_dev_info sysfs_backing_dev_info = {
         .ra_pages       = 0,    /* No readahead */
-        .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
+        .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
 };
 
 static const struct inode_operations sysfs_inode_operations ={
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index c49a2d045e11..13ab79d99268 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -12,6 +12,7 @@
 #include <linux/log2.h>
 #include <linux/proportions.h>
 #include <linux/kernel.h>
+#include <linux/fs.h>
 #include <asm/atomic.h>
 
 struct page;
@@ -151,22 +152,43 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
 
 /*
  * Flags in backing_dev_info::capability
- * - The first two flags control whether dirty pages will contribute to the
- *   VM's accounting and whether writepages() should be called for dirty pages
- *   (something that would not, for example, be appropriate for ramfs)
- * - These flags let !MMU mmap() govern direct device mapping vs immediate
- *   copying more easily for MAP_PRIVATE, especially for ROM filesystems
+ *
+ * The first three flags control whether dirty pages will contribute to the
+ * VM's accounting and whether writepages() should be called for dirty pages
+ * (something that would not, for example, be appropriate for ramfs)
+ *
+ * WARNING: these flags are closely related and should not normally be
+ * used separately.  The BDI_CAP_NO_ACCT_AND_WRITEBACK combines these
+ * three flags into a single convenience macro.
+ *
+ * BDI_CAP_NO_ACCT_DIRTY:  Dirty pages shouldn't contribute to accounting
+ * BDI_CAP_NO_WRITEBACK:   Don't write pages back
+ * BDI_CAP_NO_ACCT_WB:     Don't automatically account writeback pages
+ *
+ * These flags let !MMU mmap() govern direct device mapping vs immediate
+ * copying more easily for MAP_PRIVATE, especially for ROM filesystems.
+ *
+ * BDI_CAP_MAP_COPY:       Copy can be mapped (MAP_PRIVATE)
+ * BDI_CAP_MAP_DIRECT:     Can be mapped directly (MAP_SHARED)
+ * BDI_CAP_READ_MAP:       Can be mapped for reading
+ * BDI_CAP_WRITE_MAP:      Can be mapped for writing
+ * BDI_CAP_EXEC_MAP:       Can be mapped for execution
  */
-#define BDI_CAP_NO_ACCT_DIRTY   0x00000001      /* Dirty pages shouldn't contribute to accounting */
-#define BDI_CAP_NO_WRITEBACK    0x00000002      /* Don't write pages back */
-#define BDI_CAP_MAP_COPY        0x00000004      /* Copy can be mapped (MAP_PRIVATE) */
-#define BDI_CAP_MAP_DIRECT      0x00000008      /* Can be mapped directly (MAP_SHARED) */
-#define BDI_CAP_READ_MAP        0x00000010      /* Can be mapped for reading */
-#define BDI_CAP_WRITE_MAP       0x00000020      /* Can be mapped for writing */
-#define BDI_CAP_EXEC_MAP        0x00000040      /* Can be mapped for execution */
+#define BDI_CAP_NO_ACCT_DIRTY   0x00000001
+#define BDI_CAP_NO_WRITEBACK    0x00000002
+#define BDI_CAP_MAP_COPY        0x00000004
+#define BDI_CAP_MAP_DIRECT      0x00000008
+#define BDI_CAP_READ_MAP        0x00000010
+#define BDI_CAP_WRITE_MAP       0x00000020
+#define BDI_CAP_EXEC_MAP        0x00000040
+#define BDI_CAP_NO_ACCT_WB      0x00000080
+
 #define BDI_CAP_VMFLAGS \
         (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
 
+#define BDI_CAP_NO_ACCT_AND_WRITEBACK \
+        (BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB)
+
 #if defined(VM_MAYREAD) && \
         (BDI_CAP_READ_MAP != VM_MAYREAD || \
          BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
@@ -206,17 +228,32 @@ void clear_bdi_congested(struct backing_dev_info *bdi, int rw);
 void set_bdi_congested(struct backing_dev_info *bdi, int rw);
 long congestion_wait(int rw, long timeout);
 
-#define bdi_cap_writeback_dirty(bdi) \
-        (!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
 
-#define bdi_cap_account_dirty(bdi) \
-        (!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY))
+static inline bool bdi_cap_writeback_dirty(struct backing_dev_info *bdi)
+{
+        return !(bdi->capabilities & BDI_CAP_NO_WRITEBACK);
+}
+
+static inline bool bdi_cap_account_dirty(struct backing_dev_info *bdi)
+{
+        return !(bdi->capabilities & BDI_CAP_NO_ACCT_DIRTY);
+}
 
-#define mapping_cap_writeback_dirty(mapping) \
-        bdi_cap_writeback_dirty((mapping)->backing_dev_info)
+static inline bool bdi_cap_account_writeback(struct backing_dev_info *bdi)
+{
+        /* Paranoia: BDI_CAP_NO_WRITEBACK implies BDI_CAP_NO_ACCT_WB */
+        return !(bdi->capabilities & (BDI_CAP_NO_ACCT_WB |
+                                      BDI_CAP_NO_WRITEBACK));
+}
 
-#define mapping_cap_account_dirty(mapping) \
-        bdi_cap_account_dirty((mapping)->backing_dev_info)
+static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
+{
+        return bdi_cap_writeback_dirty(mapping->backing_dev_info);
+}
 
+static inline bool mapping_cap_account_dirty(struct address_space *mapping)
+{
+        return bdi_cap_account_dirty(mapping->backing_dev_info);
+}
 
 #endif          /* _LINUX_BACKING_DEV_H */
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index b9d467d83fc1..fbc6fc8949b4 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -575,7 +575,7 @@ static struct inode_operations cgroup_dir_inode_operations;
 static struct file_operations proc_cgroupstats_operations;
 
 static struct backing_dev_info cgroup_backing_dev_info = {
-        .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
+        .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
 };
 
 static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 2a9942f5387c..bbcb916190c9 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1246,7 +1246,7 @@ int test_clear_page_writeback(struct page *page)
                         radix_tree_tag_clear(&mapping->page_tree,
                                                 page_index(page),
                                                 PAGECACHE_TAG_WRITEBACK);
-                        if (bdi_cap_writeback_dirty(bdi)) {
+                        if (bdi_cap_account_writeback(bdi)) {
                                 __dec_bdi_stat(bdi, BDI_WRITEBACK);
                                 __bdi_writeout_inc(bdi);
                         }
@@ -1275,7 +1275,7 @@ int test_set_page_writeback(struct page *page)
                         radix_tree_tag_set(&mapping->page_tree,
                                                 page_index(page),
                                                 PAGECACHE_TAG_WRITEBACK);
-                        if (bdi_cap_writeback_dirty(bdi))
+                        if (bdi_cap_account_writeback(bdi))
                                 __inc_bdi_stat(bdi, BDI_WRITEBACK);
                 }
                 if (!PageDirty(page))
diff --git a/mm/shmem.c b/mm/shmem.c
index e6d9298aa22a..e2a6ae1a44e9 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -201,7 +201,7 @@ static struct vm_operations_struct shmem_vm_ops;
 
 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
         .ra_pages       = 0,    /* No readahead */
-        .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
+        .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
         .unplug_io_fn   = default_unplug_io_fn,
 };
 
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 50757ee3f9f3..d8aadaf2a0ba 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -33,7 +33,7 @@ static const struct address_space_operations swap_aops = {
 };
 
 static struct backing_dev_info swap_backing_dev_info = {
-        .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
+        .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
         .unplug_io_fn   = swap_unplug_io_fn,
 };