[PATCH] f2fs: return writeback error from collapse range

[Wenjie Qi]

f2fs_collapse_range() writes back pages moved by f2fs_do_collapse(),
but ignores the return value. If writeback fails, the ioctl can still
truncate page cache, shrink blocks, and report success.

Return the error before truncating page cache or updating the file size.

Fixes: b4ace3370324 ("f2fs: support FALLOC_FL_COLLAPSE_RANGE")
Cc: stable@xxxxxxxxxx
Assisted-by: Codex:gpt-5.5
Signed-off-by: Wenjie Qi <qiwenjie@xxxxxxxxxx>
---
QEMU fault injection:
- baseline: FAULT_WRITE_IO made fallocate(COLLAPSE_RANGE) return 0.
- patched: the same trigger returned -1/EIO.
- no-fault collapse returned 0 and fsck.f2fs core checks were Ok.

 fs/f2fs/file.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index c54897a25981..4bbd89320b00 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1623,11 +1623,14 @@ static int f2fs_collapse_range(struct inode *inode, loff_t offset, loff_t len)
 
 	/* write out all moved pages, if possible */
 	filemap_invalidate_lock(inode->i_mapping);
-	filemap_write_and_wait_range(inode->i_mapping, offset, LLONG_MAX);
+	ret = filemap_write_and_wait_range(inode->i_mapping, offset, LLONG_MAX);
+	if (ret)
+		goto out_unlock;
 	truncate_pagecache(inode, offset);
 
 	new_size = i_size_read(inode) - len;
 	ret = f2fs_truncate_blocks(inode, new_size, true);
+out_unlock:
 	filemap_invalidate_unlock(inode->i_mapping);
 	if (!ret)
 		f2fs_i_size_write(inode, new_size);
-- 
2.43.0