fat: additions to support fat_fallocate

[karo-tx-linux.git] / fs / fat / inode.c

diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 5d4513cb1b3c03604792f145125b21fb338a3101..99a76c274ff59dd47697ad67b5ae67cf117a8f1b 100644 (file)
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -152,11 +152,64 @@ static void fat_write_failed(struct address_space *mapping, loff_t to)
        }
 }
 
+static int fat_zero_falloc_area(struct file *file,
+                               struct address_space *mapping, loff_t pos)
+{
+       struct page *page;
+       struct inode *inode = mapping->host;
+       loff_t curpos = i_size_read(inode);
+       size_t count = pos - curpos;
+       int err;
+
+       do {
+               unsigned offset, bytes;
+               void *fsdata;
+
+               offset = (curpos & (PAGE_CACHE_SIZE - 1));
+               bytes = PAGE_CACHE_SIZE - offset;
+               bytes = min(bytes, count);
+
+               err = pagecache_write_begin(NULL, mapping, curpos, bytes,
+                                       AOP_FLAG_UNINTERRUPTIBLE,
+                                       &page, &fsdata);
+               if (err)
+                       break;
+
+               zero_user(page, offset, bytes);
+
+               err = pagecache_write_end(NULL, mapping, curpos, bytes, bytes,
+                                       page, fsdata);
+               if (err < 0)
+                       break;
+               curpos += bytes;
+               count -= bytes;
+               err = 0;
+       } while (count);
+
+       return err;
+}
+
 static int fat_write_begin(struct file *file, struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned flags,
                        struct page **pagep, void **fsdata)
 {
        int err;
+       loff_t mmu_private_ideal, mmu_private_actual;
+       loff_t size;
+       struct inode *inode = mapping->host;
+       struct super_block *sb = inode->i_sb;
+
+       size = i_size_read(inode);
+       mmu_private_actual = MSDOS_I(inode)->mmu_private;
+       mmu_private_ideal = round_up(size, sb->s_blocksize);
+       if ((mmu_private_actual > mmu_private_ideal) && (pos > size)) {
+               err = fat_zero_falloc_area(file, mapping, pos);
+               if (err) {
+                       fat_msg(sb, KERN_ERR,
+                               "Error (%d) zeroing fallocated area", err);
+                       return err;
+               }
+       }
 
        *pagep = NULL;
        err = cont_write_begin(file, mapping, pos, len, flags,