1 files changed, 50 insertions, 2 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 7875a2dd54b9..b1a6a7373f07 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2458,6 +2458,33 @@ out_writepages:
         return ret;
 }
 
+#define FALL_BACK_TO_NONDELALLOC 1
+static int ext4_nonda_switch(struct super_block *sb)
+{
+        s64 free_blocks, dirty_blocks;
+        struct ext4_sb_info *sbi = EXT4_SB(sb);
+
+        /*
+         * switch to non delalloc mode if we are running low
+         * on free block. The free block accounting via percpu
+         * counters can get slightly wrong with FBC_BATCH getting
+         * accumulated on each CPU without updating global counters
+         * Delalloc need an accurate free block accounting. So switch
+         * to non delalloc when we are near to error range.
+         */
+        free_blocks  = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
+        dirty_blocks = percpu_counter_read_positive(&sbi->s_dirtyblocks_counter);
+        if (2 * free_blocks < 3 * dirty_blocks ||
+                free_blocks < (dirty_blocks + EXT4_FREEBLOCKS_WATERMARK)) {
+                /*
+                 * free block count is less that 150% of dirty blocks
+                 * or free blocks is less that watermark
+                 */
+                return 1;
+        }
+        return 0;
+}
+
 static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
                                 loff_t pos, unsigned len, unsigned flags,
                                 struct page **pagep, void **fsdata)
@@ -2472,6 +2499,13 @@ static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
         index = pos >> PAGE_CACHE_SHIFT;
         from = pos & (PAGE_CACHE_SIZE - 1);
         to = from + len;
+
+        if (ext4_nonda_switch(inode->i_sb)) {
+                *fsdata = (void *)FALL_BACK_TO_NONDELALLOC;
+                return ext4_write_begin(file, mapping, pos,
+                                        len, flags, pagep, fsdata);
+        }
+        *fsdata = (void *)0;
 retry:
         /*
          * With delayed allocation, we don't log the i_disksize update
@@ -2540,6 +2574,19 @@ static int ext4_da_write_end(struct file *file,
         handle_t *handle = ext4_journal_current_handle();
         loff_t new_i_size;
         unsigned long start, end;
+        int write_mode = (int)(unsigned long)fsdata;
+
+        if (write_mode == FALL_BACK_TO_NONDELALLOC) {
+                if (ext4_should_order_data(inode)) {
+                        return ext4_ordered_write_end(file, mapping, pos,
+                                        len, copied, page, fsdata);
+                } else if (ext4_should_writeback_data(inode)) {
+                        return ext4_writeback_write_end(file, mapping, pos,
+                                        len, copied, page, fsdata);
+                } else {
+                        BUG();
+                }
+        }
 
         start = pos & (PAGE_CACHE_SIZE - 1);
         end = start + copied - 1;
@@ -4877,6 +4924,7 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct page *page)
         loff_t size;
         unsigned long len;
         int ret = -EINVAL;
+        void *fsdata;
         struct file *file = vma->vm_file;
         struct inode *inode = file->f_path.dentry->d_inode;
         struct address_space *mapping = inode->i_mapping;
@@ -4915,11 +4963,11 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct page *page)
          * on the same page though
          */
         ret = mapping->a_ops->write_begin(file, mapping, page_offset(page),
-                        len, AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
+                        len, AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
         if (ret < 0)
                 goto out_unlock;
         ret = mapping->a_ops->write_end(file, mapping, page_offset(page),
-                        len, len, page, NULL);
+                        len, len, page, fsdata);
         if (ret < 0)
                 goto out_unlock;
         ret = 0;