[PATCH 3/6] fs/ntfs3: grow $DATA before publishing i_size in setattr

[Kamil Chojnowski via B4 Relay]

From: Kamil Chojnowski <contact@xxxxxxxxx>

ntfs_setattr() calls truncate_setsize() and then ntfs_set_size().  When
a resident file grows, i_size is updated before the resident attribute,
so a concurrent read gets an inline mapping shorter than i_size:
iomap_read_inline_data() warns and the read fails with -EIO.

  WARNING: fs/iomap/buffered-io.c:431 at iomap_read_inline_data
   iomap_read_folio_iter
   iomap_read_folio
   ntfs_read_folio
   filemap_read_folio

attr_set_size_ex() updates i_size itself once the attribute is resized.
Call truncate_setsize() first only when shrinking; when growing, resize
the attribute first and then call pagecache_isize_extended().

Reproducer: extend a small file with ftruncate(2) in 64-byte steps while
another thread reads it; it fails within seconds.

Fixes: ecbb433f9a8e ("fs/ntfs3: fold file size handling into ntfs_set_size()")
Cc: stable@xxxxxxxxxxxxxxx
Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Kamil Chojnowski <contact@xxxxxxxxx>
---
 fs/ntfs3/file.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/fs/ntfs3/file.c b/fs/ntfs3/file.c
index 384e61a33a84..3b91586c4630 100644
--- a/fs/ntfs3/file.c
+++ b/fs/ntfs3/file.c
@@ -755,7 +755,14 @@ int ntfs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 		newsize = attr->ia_size;
 
 		if (newsize != oldsize) {
-			truncate_setsize(inode, newsize);
+			/*
+			 * Grow the attribute before i_size: read_folio maps
+			 * resident data by the attribute size and fails with
+			 * -EIO if i_size is already beyond it.  ntfs_set_size()
+			 * updates i_size.
+			 */
+			if (newsize < oldsize)
+				truncate_setsize(inode, newsize);
 
 			err = ntfs_set_size(inode, newsize);
 			if (err) {
@@ -763,6 +770,9 @@ int ntfs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 				goto out;
 			}
 
+			if (newsize > oldsize)
+				pagecache_isize_extended(inode, oldsize, newsize);
+
 			ni->std_fa |= FILE_ATTRIBUTE_ARCHIVE;
 			ni->ni_flags |= NI_FLAG_UPDATE_PARENT;
 			inode_set_mtime_to_ts(inode,

-- 
2.56.0