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>

2 files changed, 84 insertions, 0 deletions

diff --git a/fs/iomap.c b/fs/iomap.c
index 706270f21b35..e9b3f991c2d8 100644
--- 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 3d70ece10313..3a56212a0a8d 100644
--- 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,