1 files changed, 63 insertions, 0 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 7c54ae5fcbd4..a569b66103a3 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -31,6 +31,7 @@
 #include <linux/writeback.h>
 #include <linux/pagevec.h>
 #include <linux/mpage.h>
+#include <linux/rmap.h>
 #include <linux/namei.h>
 #include <linux/uio.h>
 #include <linux/bio.h>
@@ -3902,6 +3903,68 @@ int ext4_update_disksize_before_punch(struct inode *inode, loff_t offset,
 	return ret;
 }
 
+static inline void ext4_truncate_folio(struct inode *inode,
+				       loff_t start, loff_t end)
+{
+	unsigned long blocksize = i_blocksize(inode);
+	struct folio *folio;
+
+	/* Nothing to be done if no complete block needs to be truncated. */
+	if (round_up(start, blocksize) >= round_down(end, blocksize))
+		return;
+
+	folio = filemap_lock_folio(inode->i_mapping, start >> PAGE_SHIFT);
+	if (IS_ERR(folio))
+		return;
+
+	if (folio_mkclean(folio))
+		folio_mark_dirty(folio);
+	folio_unlock(folio);
+	folio_put(folio);
+}
+
+int ext4_truncate_page_cache_block_range(struct inode *inode,
+					 loff_t start, loff_t end)
+{
+	unsigned long blocksize = i_blocksize(inode);
+	int ret;
+
+	/*
+	 * For journalled data we need to write (and checkpoint) pages
+	 * before discarding page cache to avoid inconsitent data on disk
+	 * in case of crash before freeing or unwritten converting trans
+	 * is committed.
+	 */
+	if (ext4_should_journal_data(inode)) {
+		ret = filemap_write_and_wait_range(inode->i_mapping, start,
+						   end - 1);
+		if (ret)
+			return ret;
+		goto truncate_pagecache;
+	}
+
+	/*
+	 * If the block size is less than the page size, the file's mapped
+	 * blocks within one page could be freed or converted to unwritten.
+	 * So it's necessary to remove writable userspace mappings, and then
+	 * ext4_page_mkwrite() can be called during subsequent write access
+	 * to these partial folios.
+	 */
+	if (!IS_ALIGNED(start | end, PAGE_SIZE) &&
+	    blocksize < PAGE_SIZE && start < inode->i_size) {
+		loff_t page_boundary = round_up(start, PAGE_SIZE);
+
+		ext4_truncate_folio(inode, start, min(page_boundary, end));
+		if (end > page_boundary)
+			ext4_truncate_folio(inode,
+					    round_down(end, PAGE_SIZE), end);
+	}
+
+truncate_pagecache:
+	truncate_pagecache_range(inode, start, end - 1);
+	return 0;
+}
+
 static void ext4_wait_dax_page(struct inode *inode)
 {
 	filemap_invalidate_unlock(inode->i_mapping);