Re: [PATCH 6.6 440/744] fs: move kiocb_start_write() into vfs_iocb_iter_write()

On Thu, Jun 6, 2024 at 5:18 PM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:

6.6-stable review patch. If anyone has any objections, please let me know.

I have objections and I wrote them when Sasha posted the patch for review:

https://lore.kernel.org/stable/CAOQ4uxg1Ce31UDDeb9ADYgEBvr582j4hqmJ-B72iAL+2...

Where did this objection get lost?

Thanks, Amir.

---

From: Amir Goldstein amir73il@gmail.com

[ Upstream commit 6ae654392bb516a0baa47fed1f085d84e8cad739 ]

In vfs code, sb_start_write() is usually called after the permission hook in rw_verify_area(). vfs_iocb_iter_write() is an exception to this rule, where kiocb_start_write() is called by its callers.

Move kiocb_start_write() from the callers into vfs_iocb_iter_write() after the rw_verify_area() checks, to make them "start-write-safe".

The semantics of vfs_iocb_iter_write() is changed, so that the caller is responsible for calling kiocb_end_write() on completion only if async iocb was queued. The completion handlers of both callers were adapted to this semantic change.

This is needed for fanotify "pre content" events.

Suggested-by: Jan Kara jack@suse.cz Suggested-by: Josef Bacik josef@toxicpanda.com Signed-off-by: Amir Goldstein amir73il@gmail.com Link: https://lore.kernel.org/r/20231122122715.2561213-14-amir73il@gmail.com Reviewed-by: Josef Bacik josef@toxicpanda.com Reviewed-by: Jan Kara jack@suse.cz Signed-off-by: Christian Brauner brauner@kernel.org Stable-dep-of: 7c98f7cb8fda ("remove call_{read,write}_iter() functions") Signed-off-by: Sasha Levin sashal@kernel.org

---

fs/cachefiles/io.c | 5 ++--- fs/overlayfs/file.c | 8 ++++---- fs/read_write.c | 7 +++++++ 3 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c index 009d23cd435b5..5857241c59181 100644 --- a/fs/cachefiles/io.c +++ b/fs/cachefiles/io.c @@ -259,7 +259,8 @@ static void cachefiles_write_complete(struct kiocb *iocb, long ret)

    _enter("%ld", ret);

•   kiocb_end_write(iocb);
  

•   if (ki->was_async)
  

•           kiocb_end_write(iocb);
  
    if (ret < 0)
            trace_cachefiles_io_error(object, inode, ret,
  

@@ -319,8 +320,6 @@ int __cachefiles_write(struct cachefiles_object *object, ki->iocb.ki_complete = cachefiles_write_complete; atomic_long_add(ki->b_writing, &cache->b_writing);

•   kiocb_start_write(&ki->iocb);
  

•   get_file(ki->iocb.ki_filp);
    cachefiles_grab_object(object, cachefiles_obj_get_ioreq);
  
  

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c index 9fd88579bfbfb..a1c64c2b8e204 100644 --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -295,10 +295,8 @@ static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req) struct kiocb *iocb = &aio_req->iocb; struct kiocb *orig_iocb = aio_req->orig_iocb;

•   if (iocb->ki_flags & IOCB_WRITE) {
  

•           kiocb_end_write(iocb);
  

•   if (iocb->ki_flags & IOCB_WRITE)
            ovl_file_modified(orig_iocb->ki_filp);
  

•   }
  
    orig_iocb->ki_pos = iocb->ki_pos;
    ovl_aio_put(aio_req);
  

@@ -310,6 +308,9 @@ static void ovl_aio_rw_complete(struct kiocb *iocb, long res) struct ovl_aio_req, iocb); struct kiocb *orig_iocb = aio_req->orig_iocb;

•   if (iocb->ki_flags & IOCB_WRITE)
  

•           kiocb_end_write(iocb);
  

•   ovl_aio_cleanup_handler(aio_req);
    orig_iocb->ki_complete(orig_iocb, res);
  

} @@ -421,7 +422,6 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter) aio_req->iocb.ki_flags = ifl; aio_req->iocb.ki_complete = ovl_aio_rw_complete; refcount_set(&aio_req->ref, 2);

•           kiocb_start_write(&aio_req->iocb);
            ret = vfs_iocb_iter_write(real.file, &aio_req->iocb, iter);
            ovl_aio_put(aio_req);
            if (ret != -EIOCBQUEUED)
  

diff --git a/fs/read_write.c b/fs/read_write.c index 4771701c896ba..9a56949f3b8d1 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -865,6 +865,10 @@ static ssize_t do_iter_write(struct file *file, struct iov_iter *iter, return ret; }

+/*

• • Caller is responsible for calling kiocb_end_write() on completion
• • if async iocb was queued.
• */

ssize_t vfs_iocb_iter_write(struct file *file, struct kiocb *iocb, struct iov_iter *iter) { @@ -885,7 +889,10 @@ ssize_t vfs_iocb_iter_write(struct file *file, struct kiocb *iocb, if (ret < 0) return ret;

•   kiocb_start_write(iocb);
    ret = call_write_iter(file, iocb, iter);
  

•   if (ret != -EIOCBQUEUED)
  

•           kiocb_end_write(iocb);
    if (ret > 0)
            fsnotify_modify(file);
  
  

-- 2.43.0