Fixes for 5.16-rc2:

- Fix an accounting problem where unaligned inline data reads can run
    off the end of the read iomap iterator.  iomap has historically
    required that inline data mappings only exist at the end of a file,
    though this wasn't documented anywhere.
  - Document iomap_read_inline_data and change its return type to be
    appropriate for the information that it's actually returning.
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Merge tag 'iomap-5.16-fixes-1' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux

Pull iomap fixes from Darrick Wong:
 "A single iomap bug fix and a cleanup for 5.16-rc2.

  The bug fix changes how iomap deals with reading from an inline data
  region -- whereas the current code (incorrectly) lets the iomap read
  iter try for more bytes after reading the inline region (which zeroes
  the rest of the page!) and hopes the next iteration terminates, we
  surveyed the inlinedata implementations and realized that all
  inlinedata implementations also require that the inlinedata region end
  at EOF, so we can simply terminate the read.

  The second patch documents these assumptions in the code so that
  they're not subtle implications anymore, and cleans up some of the
  grosser parts of that function.

  Summary:

   - Fix an accounting problem where unaligned inline data reads can run
     off the end of the read iomap iterator. iomap has historically
     required that inline data mappings only exist at the end of a file,
     though this wasn't documented anywhere.

   - Document iomap_read_inline_data and change its return type to be
     appropriate for the information that it's actually returning"

* tag 'iomap-5.16-fixes-1' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  iomap: iomap_read_inline_data cleanup
  iomap: Fix inline extent handling in iomap_readpage

fs/iomap/buffered-io.c

@@ -205,7 +205,16 @@ struct iomap_readpage_ctx {
 	struct readahead_control *rac;
 };
 
-static loff_t iomap_read_inline_data(const struct iomap_iter *iter,
+/**
+ * iomap_read_inline_data - copy inline data into the page cache
+ * @iter: iteration structure
+ * @page: page to copy to
+ *
+ * Copy the inline data in @iter into @page and zero out the rest of the page.
+ * Only a single IOMAP_INLINE extent is allowed at the end of each file.
+ * Returns zero for success to complete the read, or the usual negative errno.
+ */
+static int iomap_read_inline_data(const struct iomap_iter *iter,
 		struct page *page)
 {
 	const struct iomap *iomap = iomap_iter_srcmap(iter);
@@ -214,7 +223,7 @@ static loff_t iomap_read_inline_data(const struct iomap_iter *iter,
 	void *addr;
 
 	if (PageUptodate(page))
-		return PAGE_SIZE - poff;
+		return 0;
 
 	if (WARN_ON_ONCE(size > PAGE_SIZE - poff))
 		return -EIO;
@@ -231,7 +240,7 @@ static loff_t iomap_read_inline_data(const struct iomap_iter *iter,
 	memset(addr + size, 0, PAGE_SIZE - poff - size);
 	kunmap_local(addr);
 	iomap_set_range_uptodate(page, poff, PAGE_SIZE - poff);
-	return PAGE_SIZE - poff;
+	return 0;
 }
 
 static inline bool iomap_block_needs_zeroing(const struct iomap_iter *iter,
@@ -257,7 +266,7 @@ static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
 	sector_t sector;
 
 	if (iomap->type == IOMAP_INLINE)
-		return min(iomap_read_inline_data(iter, page), length);
+		return iomap_read_inline_data(iter, page);
 
 	/* zero post-eof blocks as the page may be mapped */
 	iop = iomap_page_create(iter->inode, page);
@@ -370,6 +379,8 @@ static loff_t iomap_readahead_iter(const struct iomap_iter *iter,
 			ctx->cur_page_in_bio = false;
 		}
 		ret = iomap_readpage_iter(iter, ctx, done);
+		if (ret <= 0)
+			return ret;
 	}
 
 	return done;
@@ -580,15 +591,10 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
 static int iomap_write_begin_inline(const struct iomap_iter *iter,
 		struct page *page)
 {
-	int ret;
-
 	/* needs more work for the tailpacking case; disable for now */
 	if (WARN_ON_ONCE(iomap_iter_srcmap(iter)->offset != 0))
 		return -EIO;
-	ret = iomap_read_inline_data(iter, page);
-	if (ret < 0)
-		return ret;
-	return 0;
+	return iomap_read_inline_data(iter, page);
 }
 
 static int iomap_write_begin(const struct iomap_iter *iter, loff_t pos,