6.15-stable review patch. If anyone has any objections, please let me know.
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From: Zizhi Wo wozizhi@huawei.com
[ 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 wozizhi@huawei.com Link: https://lore.kernel.org/20250703024418.2809353-1-wozizhi@huaweicloud.com Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 c08e4a66ac07a..3e0576d9db1d2 100644 --- a/fs/cachefiles/io.c +++ b/fs/cachefiles/io.c @@ -347,8 +347,6 @@ 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 d9bc671761282..a7ed86fa98bb8 100644 --- a/fs/cachefiles/ondemand.c +++ b/fs/cachefiles/ondemand.c @@ -83,10 +83,8 @@ 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);