[PATCH v2] coda: honor the append state of each write

[Hungyu Lin <dennylin0707@gmail.com>]

coda_open() adds O_APPEND to the container file's f_flags after it has
been opened, without updating its cached f_iocb_flags. An O_APPEND write
can therefore overwrite existing data instead of appending. For example,
writing "Z" to a file containing "abc" produces "Zbc" rather than "abcZ".

Pass RWF_APPEND or RWF_NOAPPEND to vfs_iter_write() according to the
incoming IOCB_APPEND state. This also honors changes made with F_SETFL
and per-write append overrides instead of relying on the container's
open-time flags.

Fixes: 164f4064ca81 ("keep iocb_flags() result cached in struct file")
Cc: stable@vger.kernel.org # 6.9+
Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>
---
Changes in v2:
- Keep cfi->cfi_container as the vfs_iter_write() argument.

 fs/coda/file.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/coda/file.c b/fs/coda/file.c
index 6ca8bfcb58f2..c9fba41f7cea 100644
--- a/fs/coda/file.c
+++ b/fs/coda/file.c
@@ -71,6 +71,7 @@ coda_file_write_iter(struct kiocb *iocb, struct iov_iter *to)
 	struct file *host_file = cfi->cfi_container;
 	loff_t ki_pos = iocb->ki_pos;
 	size_t count = iov_iter_count(to);
+	rwf_t flags = (iocb->ki_flags & IOCB_APPEND) ? RWF_APPEND : RWF_NOAPPEND;
 	ssize_t ret;
 
 	ret = venus_access_intent(coda_inode->i_sb, coda_i2f(coda_inode),
@@ -80,7 +81,7 @@ coda_file_write_iter(struct kiocb *iocb, struct iov_iter *to)
 		goto finish_write;
 
 	inode_lock(coda_inode);
-	ret = vfs_iter_write(cfi->cfi_container, to, &iocb->ki_pos, 0);
+	ret = vfs_iter_write(cfi->cfi_container, to, &iocb->ki_pos, flags);
 	coda_inode->i_size = file_inode(host_file)->i_size;
 	coda_inode->i_blocks = (coda_inode->i_size + 511) >> 9;
 	inode_set_mtime_to_ts(coda_inode, inode_set_ctime_current(coda_inode));

base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
-- 
2.43.0