5 files changed, 18 insertions, 46 deletions
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 5da6012b7a14..e936cea856dc 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -238,8 +238,6 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
 * BDI_CAP_WRITE_MAP:      Can be mapped for writing
 * BDI_CAP_EXEC_MAP:       Can be mapped for execution
 *
- * BDI_CAP_SWAP_BACKED:    Count shmem/tmpfs objects as swap-backed.
- *
 * BDI_CAP_STRICTLIMIT:    Keep number of dirty pages below bdi threshold.
 */
 #define BDI_CAP_NO_ACCT_DIRTY   0x00000001
@@ -250,7 +248,6 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
 #define BDI_CAP_WRITE_MAP       0x00000020
 #define BDI_CAP_EXEC_MAP        0x00000040
 #define BDI_CAP_NO_ACCT_WB      0x00000080
-#define BDI_CAP_SWAP_BACKED     0x00000100
 #define BDI_CAP_STABLE_WRITES   0x00000200
 #define BDI_CAP_STRICTLIMIT     0x00000400
@@ -329,11 +326,6 @@ static inline bool bdi_cap_account_writeback(struct backing_dev_info *bdi)
                                      BDI_CAP_NO_WRITEBACK));
 }
-static inline bool bdi_cap_swap_backed(struct backing_dev_info *bdi)
-{
-        return bdi->capabilities & BDI_CAP_SWAP_BACKED;
-}
 static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
 {
        return bdi_cap_writeback_dirty(mapping->backing_dev_info);
@@ -344,11 +336,6 @@ static inline bool mapping_cap_account_dirty(struct address_space *mapping)
        return bdi_cap_account_dirty(mapping->backing_dev_info);
 }
-static inline bool mapping_cap_swap_backed(struct address_space *mapping)
-{
-        return bdi_cap_swap_backed(mapping->backing_dev_info);
-}
 static inline int bdi_sched_wait(void *word)
 {
        schedule();
diff --git a/mm/madvise.c b/mm/madvise.c
index a271adc93289..1383a8916bc3 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -222,19 +222,22 @@ static long madvise_willneed(struct vm_area_struct *vma,
        struct file *file = vma->vm_file;
 #ifdef CONFIG_SWAP
-        if (!file || mapping_cap_swap_backed(file->f_mapping)) {
+        if (!file) {
                *prev = vma;
-                if (!file)
+                force_swapin_readahead(vma, start, end);
-                        force_swapin_readahead(vma, start, end);
-                else
-                        force_shm_swapin_readahead(vma, start, end,
-                                                file->f_mapping);
                return 0;
        }
-#endif
+        if (shmem_mapping(file->f_mapping)) {
+                *prev = vma;
+                force_shm_swapin_readahead(vma, start, end,
+                                        file->f_mapping);
+                return 0;
+        }
+#else
        if (!file)
                return -EBADF;
+#endif
        if (file->f_mapping->a_ops->get_xip_mem) {
                /* no bad return value, but ignore advice */
diff --git a/mm/shmem.c b/mm/shmem.c
index 73ba1df7c8ba..1b77eaf589fd 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -191,11 +191,6 @@ static const struct inode_operations shmem_dir_inode_operations;
 static const struct inode_operations shmem_special_inode_operations;
 static const 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_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
-};
 static LIST_HEAD(shmem_swaplist);
 static DEFINE_MUTEX(shmem_swaplist_mutex);
@@ -765,11 +760,11 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
                goto redirty;
        /*
-         * shmem_backing_dev_info's capabilities prevent regular writeback or
+         * Our capabilities prevent regular writeback or sync from ever calling
-         * sync from ever calling shmem_writepage; but a stacking filesystem
+         * shmem_writepage; but a stacking filesystem might use ->writepage of
-         * might use ->writepage of its underlying filesystem, in which case
+         * its underlying filesystem, in which case tmpfs should write out to
-         * tmpfs should write out to swap only in response to memory pressure,
+         * swap only in response to memory pressure, and not for the writeback
-         * and not for the writeback threads or sync.
+         * threads or sync.
         */
        if (!wbc->for_reclaim) {
                WARN_ON_ONCE(1);        /* Still happens? Tell us about it! */
@@ -1415,7 +1410,7 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode
                inode->i_ino = get_next_ino();
                inode_init_owner(inode, dir, mode);
                inode->i_blocks = 0;
-                inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
+                inode->i_mapping->backing_dev_info = &noop_backing_dev_info;
                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
                inode->i_generation = get_seconds();
                info = SHMEM_I(inode);
@@ -1461,7 +1456,7 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode
 bool shmem_mapping(struct address_space *mapping)
 {
-        return mapping->backing_dev_info == &shmem_backing_dev_info;
+        return mapping->host->i_sb->s_op == &shmem_ops;
 }
 #ifdef CONFIG_TMPFS
@@ -3226,10 +3221,6 @@ int __init shmem_init(void)
        if (shmem_inode_cachep)
                return 0;
-        error = bdi_init(&shmem_backing_dev_info);
-        if (error)
-                goto out4;
        error = shmem_init_inodecache();
        if (error)
                goto out3;
@@ -3253,8 +3244,6 @@ out1:
 out2:
        shmem_destroy_inodecache();
 out3:
-        bdi_destroy(&shmem_backing_dev_info);
-out4:
        shm_mnt = ERR_PTR(error);
        return error;
 }
diff --git a/mm/swap.c b/mm/swap.c
index 8a12b33936b4..4e0109a2f37b 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -1138,8 +1138,6 @@ void __init swap_setup(void)
 #ifdef CONFIG_SWAP
        int i;
-        if (bdi_init(swapper_spaces[0].backing_dev_info))
-                panic("Failed to init swap bdi");
        for (i = 0; i < MAX_SWAPFILES; i++) {
                spin_lock_init(&swapper_spaces[i].tree_lock);
                INIT_LIST_HEAD(&swapper_spaces[i].i_mmap_nonlinear);
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 9711342987a0..1c137b69ecde 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -32,17 +32,12 @@ static const struct address_space_operations swap_aops = {
 #endif
 };
-static struct backing_dev_info swap_backing_dev_info = {
-        .name           = "swap",
-        .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
-};
 struct address_space swapper_spaces[MAX_SWAPFILES] = {
        [0 ... MAX_SWAPFILES - 1] = {
                .page_tree      = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN),
                .i_mmap_writable = ATOMIC_INIT(0),
                .a_ops          = &swap_aops,
-                .backing_dev_info = &swap_backing_dev_info,
+                .backing_dev_info = &noop_backing_dev_info,
        }
 };