5 files changed, 43 insertions, 20 deletions

diff --git a/fs/dax.c b/fs/dax.c
index 1a2bdbfa3ea9..69c3126a05b4 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -20,8 +20,45 @@
 #include <linux/fs.h>
 #include <linux/genhd.h>
 #include <linux/mutex.h>
+#include <linux/sched.h>
 #include <linux/uio.h>
 
+int dax_clear_blocks(struct inode *inode, sector_t block, long size)
+{
+        struct block_device *bdev = inode->i_sb->s_bdev;
+        sector_t sector = block << (inode->i_blkbits - 9);
+
+        might_sleep();
+        do {
+                void *addr;
+                unsigned long pfn;
+                long count;
+
+                count = bdev_direct_access(bdev, sector, &addr, &pfn, size);
+                if (count < 0)
+                        return count;
+                BUG_ON(size < count);
+                while (count > 0) {
+                        unsigned pgsz = PAGE_SIZE - offset_in_page(addr);
+                        if (pgsz > count)
+                                pgsz = count;
+                        if (pgsz < PAGE_SIZE)
+                                memset(addr, 0, pgsz);
+                        else
+                                clear_page(addr);
+                        addr += pgsz;
+                        size -= pgsz;
+                        count -= pgsz;
+                        BUG_ON(pgsz & 511);
+                        sector += pgsz / 512;
+                        cond_resched();
+                }
+        } while (size);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(dax_clear_blocks);
+
 static long dax_get_addr(struct buffer_head *bh, void **addr, unsigned blkbits)
 {
         unsigned long pfn;
diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 3ccd5fd47d66..52978b853226 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -733,10 +733,12 @@ static int ext2_get_blocks(struct inode *inode,
 
         if (IS_DAX(inode)) {
                 /*
-                 * we need to clear the block
+                 * block must be initialised before we put it in the tree
+                 * so that it's not found by another thread before it's
+                 * initialised
                  */
-                err = ext2_clear_xip_target (inode,
-                        le32_to_cpu(chain[depth-1].key));
+                err = dax_clear_blocks(inode, le32_to_cpu(chain[depth-1].key),
+                                                1 << inode->i_blkbits);
                 if (err) {
                         mutex_unlock(&ei->truncate_mutex);
                         goto cleanup;
diff --git a/fs/ext2/xip.c b/fs/ext2/xip.c
index bbc5fec6ff7f..8cfca3a4cd58 100644
--- a/fs/ext2/xip.c
+++ b/fs/ext2/xip.c
@@ -42,20 +42,6 @@ __ext2_get_block(struct inode *inode, pgoff_t pgoff, int create,
         return rc;
 }
 
-int
-ext2_clear_xip_target(struct inode *inode, sector_t block)
-{
-        void *kaddr;
-        unsigned long pfn;
-        long size;
-
-        size = __inode_direct_access(inode, block, &kaddr, &pfn, PAGE_SIZE);
-        if (size < 0)
-                return size;
-        clear_page(kaddr);
-        return 0;
-}
-
 void ext2_xip_verify_sb(struct super_block *sb)
 {
         struct ext2_sb_info *sbi = EXT2_SB(sb);
diff --git a/fs/ext2/xip.h b/fs/ext2/xip.h
index 29be73781419..b2592f2f3c9d 100644
--- a/fs/ext2/xip.h
+++ b/fs/ext2/xip.h
@@ -7,8 +7,6 @@
 
 #ifdef CONFIG_EXT2_FS_XIP
 extern void ext2_xip_verify_sb (struct super_block *);
-extern int ext2_clear_xip_target (struct inode *, sector_t);
-
 static inline int ext2_use_xip (struct super_block *sb)
 {
         struct ext2_sb_info *sbi = EXT2_SB(sb);
@@ -19,6 +17,5 @@ int ext2_get_xip_mem(struct address_space *, pgoff_t, int,
 #else
 #define ext2_xip_verify_sb(sb)                  do { } while (0)
 #define ext2_use_xip(sb)                        0
-#define ext2_clear_xip_target(inode, chain)     0
 #define ext2_get_xip_mem                        NULL
 #endif
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 241c3c030fb5..8084934a5676 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2589,6 +2589,7 @@ extern int nonseekable_open(struct inode * inode, struct file * filp);
 
 ssize_t dax_do_io(int rw, struct kiocb *, struct inode *, struct iov_iter *,
                 loff_t, get_block_t, dio_iodone_t, int flags);
+int dax_clear_blocks(struct inode *, sector_t block, long size);
 
 #ifdef CONFIG_FS_XIP
 extern int xip_file_mmap(struct file * file, struct vm_area_struct * vma);