netfs: Fix partial invalidation of streaming-write folio

In netfs_invalidate_folio(), if the region of a partial invalidation
overlaps the front (but not all) of a dirty write cached in a streaming
write page (dirty, but not uptodate, with the dirty region tracked by a
netfs_folio struct), the function modifies the dirty region - but
incorrectly as it moves the region forward by setting the start to the
start, not the end, of the invalidation region.

Fix this by setting finfo->dirty_offset to the end of the invalidation
region (iend).

Fixes: cce6bfa6ca0e ("netfs: Fix trimming of streaming-write folios in netfs_inval_folio()")
Closes: https://sashiko.dev/#/patchset/20260414082004.3756080-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://patch.msgid.link/20260512123404.719402-21-dhowells@redhat.com
cc: Paulo Alcantara <pc@manguebit.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c
index 24b20e80e9a8a5178dfe89ebc9377c70977a9e19..5d554512ed23a24ea94290134e8ec7c4cc6a2a38 100644 (file)
--- a/fs/netfs/misc.c
+++ b/fs/netfs/misc.c
@@ -262,7 +262,7 @@ void netfs_invalidate_folio(struct folio *folio, size_t offset, size_t length)
                                goto erase_completely;
                        /* Move the start of the data. */
                        finfo->dirty_len = fend - iend;
-                       finfo->dirty_offset = offset;
+                       finfo->dirty_offset = iend;
                        trace_netfs_folio(folio, netfs_folio_trace_invalidate_front);
                        return;
                }