Re: Patch "fs: move kiocb_start_write() into vfs_iocb_iter_write()" has been added to the 6.6-stable tree

On Thu, May 30, 2024 at 10:05 PM Sasha Levin sashal@kernel.org wrote:

This is a note to let you know that I've just added the patch titled

fs: move kiocb_start_write() into vfs_iocb_iter_write()

to the 6.6-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: fs-move-kiocb_start_write-into-vfs_iocb_iter_write.patch and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

commit 17f38d69e7960a2b346db04750b0e4ba867c0b83 Author: Amir Goldstein amir73il@gmail.com Date: Wed Nov 22 14:27:12 2023 +0200

fs: move kiocb_start_write() into vfs_iocb_iter_write()

[ 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 comment about semantics change looks like a clue from my past self that backporting this commit as standalone is risky.

This commit was part of a pretty big shuffle in splice and ovl code. I'd feel much more comfortable with backporting the entire ovl series 14ab6d425e8067..5b02bfc1e7e3 and splice series v6.7..6ae654392bb51 than just 3 individual commits in the middle.

Thanks, Amir.

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>

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);