fs: add iomap_file_dirty

Originally-From: Christoph Hellwig <hch@lst.de>

This function uses the iomap infrastructure to re-write all pages
in a given range.  This is useful for doing a copy-up of COW ranges,
and might be useful for scrubbing in the future.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/fs/iomap.c b/fs/iomap.c
index 706270f..e9b3f99 100644 (file)
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -252,6 +252,88 @@ iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *iter,
 }
 EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
 
+static struct page *
+__iomap_read_page(struct inode *inode, loff_t offset)
+{
+       struct address_space *mapping = inode->i_mapping;
+       struct page *page;
+
+       page = read_mapping_page(mapping, offset >> PAGE_SHIFT, NULL);
+       if (IS_ERR(page))
+               return page;
+       if (!PageUptodate(page)) {
+               put_page(page);
+               return ERR_PTR(-EIO);
+       }
+       return page;
+}
+
+static loff_t
+iomap_dirty_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
+               struct iomap *iomap)
+{
+       long status = 0;
+       ssize_t written = 0;
+
+       do {
+               struct page *page, *rpage;
+               unsigned long offset;   /* Offset into pagecache page */
+               unsigned long bytes;    /* Bytes to write to page */
+
+               offset = (pos & (PAGE_SIZE - 1));
+               bytes = min_t(unsigned long, PAGE_SIZE - offset, length);
+
+               rpage = __iomap_read_page(inode, pos);
+               if (IS_ERR(rpage))
+                       return PTR_ERR(rpage);
+
+               status = iomap_write_begin(inode, pos, bytes,
+                               AOP_FLAG_NOFS | AOP_FLAG_UNINTERRUPTIBLE,
+                               &page, iomap);
+               put_page(rpage);
+               if (unlikely(status))
+                       return status;
+
+               WARN_ON_ONCE(!PageUptodate(page));
+
+               status = iomap_write_end(inode, pos, bytes, bytes, page);
+               if (unlikely(status <= 0)) {
+                       if (WARN_ON_ONCE(status == 0))
+                               return -EIO;
+                       return status;
+               }
+
+               cond_resched();
+
+               pos += status;
+               written += status;
+               length -= status;
+
+               balance_dirty_pages_ratelimited(inode->i_mapping);
+       } while (length);
+
+       return written;
+}
+
+int
+iomap_file_dirty(struct inode *inode, loff_t pos, loff_t len,
+               struct iomap_ops *ops)
+{
+       loff_t ret;
+
+       while (len) {
+               ret = iomap_apply(inode, pos, len, IOMAP_WRITE, ops, NULL,
+                               iomap_dirty_actor);
+               if (ret <= 0)
+                       return ret;
+               pos += ret;
+               len -= ret;
+       }
+
+       return 0;
+}
+EXPORT_SYMBOL_GPL(iomap_file_dirty);
+
 static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
                unsigned bytes, struct iomap *iomap)
 {

diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 3d70ece..3a56212 100644 (file)
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -64,6 +64,8 @@ struct iomap_ops {
 
 ssize_t iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *from,
                struct iomap_ops *ops);
+int iomap_file_dirty(struct inode *inode, loff_t pos, loff_t len,
+               struct iomap_ops *ops);
 int iomap_zero_range(struct inode *inode, loff_t pos, loff_t len,
                bool *did_zero, struct iomap_ops *ops);
 int iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,