From bc016b7842f65cc7fab76fb6326f5109b2e1bb38 Mon Sep 17 00:00:00 2001 From: Zizhi Wo Date: Thu, 3 Jul 2025 10:44:18 +0800 Subject: [PATCH] cachefiles: Fix the incorrect return value in __cachefiles_write() [ Upstream commit 6b89819b06d8d339da414f06ef3242f79508be5e ] In __cachefiles_write(), if the return value of the write operation > 0, it is set to 0. This makes it impossible to distinguish scenarios where a partial write has occurred, and will affect the outer calling functions: 1) cachefiles_write_complete() will call "term_func" such as netfs_write_subrequest_terminated(). When "ret" in __cachefiles_write() is used as the "transferred_or_error" of this function, it can not distinguish the amount of data written, makes the WARN meaningless. 2) cachefiles_ondemand_fd_write_iter() can only assume all writes were successful by default when "ret" is 0, and unconditionally return the full length specified by user space. Fix it by modifying "ret" to reflect the actual number of bytes written. Furthermore, returning a value greater than 0 from __cachefiles_write() does not affect other call paths, such as cachefiles_issue_write() and fscache_write(). Fixes: 047487c947e8 ("cachefiles: Implement the I/O routines") Signed-off-by: Zizhi Wo Link: https://lore.kernel.org/20250703024418.2809353-1-wozizhi@huaweicloud.com Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin --- fs/cachefiles/io.c | 2 -- fs/cachefiles/ondemand.c | 4 +--- 2 files changed, 1 insertion(+), 5 deletions(-) diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c index 009d23cd435b..239a6002083d 100644 --- a/fs/cachefiles/io.c +++ b/fs/cachefiles/io.c @@ -346,8 +346,6 @@ int __cachefiles_write(struct cachefiles_object *object, default: ki->was_async = false; cachefiles_write_complete(&ki->iocb, ret); - if (ret > 0) - ret = 0; break; } diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c index 3389a373faf6..cfa8f23fdfb6 100644 --- a/fs/cachefiles/ondemand.c +++ b/fs/cachefiles/ondemand.c @@ -84,10 +84,8 @@ static ssize_t cachefiles_ondemand_fd_write_iter(struct kiocb *kiocb, trace_cachefiles_ondemand_fd_write(object, file_inode(file), pos, len); ret = __cachefiles_write(object, file, pos, iter, NULL, NULL); - if (!ret) { - ret = len; + if (ret > 0) kiocb->ki_pos += ret; - } out: fput(file);