Re: [PATCH RESEND V12 1/8] fs: Generic function to convert iocb to rw flags

[Rokudo Yan]

On 1/26/21 12:46 AM, Alessio Balsini wrote:
> On Mon, Jan 25, 2021 at 03:30:50PM +0000, Alessio Balsini wrote:
> > OverlayFS implements its own function to translate iocb flags into rw
> > flags, so that they can be passed into another vfs call.
> > With commit ce71bfea207b4 ("fs: align IOCB_* flags with RWF_* flags")
> > Jens created a 1:1 matching between the iocb flags and rw flags,
> > simplifying the conversion.
> >
> > Reduce the OverlayFS code by making the flag conversion function generic
> > and reusable.
> >
> > Signed-off-by: Alessio Balsini <balsini@xxxxxxxxxxx>
> > ---
> >   fs/overlayfs/file.c | 23 +++++------------------
> >   include/linux/fs.h  |  5 +++++
> >   2 files changed, 10 insertions(+), 18 deletions(-)
> >
> > diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> > index bd9dd38347ae..56be2ffc5a14 100644
> > --- a/fs/overlayfs/file.c
> > +++ b/fs/overlayfs/file.c
> > @@ -15,6 +15,8 @@
> >   #include <linux/fs.h>
> >   #include "overlayfs.h"
> >   
> > +#define OVL_IOCB_MASK (IOCB_DSYNC | IOCB_HIPRI | IOCB_NOWAIT | IOCB_SYNC)
> > +
> >   struct ovl_aio_req {
> >   	struct kiocb iocb;
> >   	struct kiocb *orig_iocb;
> > @@ -236,22 +238,6 @@ static void ovl_file_accessed(struct file *file)
> >   	touch_atime(&file->f_path);
> >   }
> >   
> > -static rwf_t ovl_iocb_to_rwf(int ifl)
> > -{
> > -	rwf_t flags = 0;
> > -
> > -	if (ifl & IOCB_NOWAIT)
> > -		flags |= RWF_NOWAIT;
> > -	if (ifl & IOCB_HIPRI)
> > -		flags |= RWF_HIPRI;
> > -	if (ifl & IOCB_DSYNC)
> > -		flags |= RWF_DSYNC;
> > -	if (ifl & IOCB_SYNC)
> > -		flags |= RWF_SYNC;
> > -
> > -	return flags;
> > -}
> > -
> >   static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
> >   {
> >   	struct kiocb *iocb = &aio_req->iocb;
> > @@ -299,7 +285,8 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
> >   	old_cred = ovl_override_creds(file_inode(file)->i_sb);
> >   	if (is_sync_kiocb(iocb)) {
> >   		ret = vfs_iter_read(real.file, iter, &iocb->ki_pos,
> > -				    ovl_iocb_to_rwf(iocb->ki_flags));
> > +				    iocb_to_rw_flags(iocb->ki_flags,
> > +						     OVL_IOCB_MASK));
> >   	} else {
> >   		struct ovl_aio_req *aio_req;
> >   
> > @@ -356,7 +343,7 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
> >   	if (is_sync_kiocb(iocb)) {
> >   		file_start_write(real.file);
> >   		ret = vfs_iter_write(real.file, iter, &iocb->ki_pos,
> > -				     ovl_iocb_to_rwf(ifl));
> > +				     iocb_to_rw_flags(ifl, OVL_IOCB_MASK));
> >   		file_end_write(real.file);
> >   		/* Update size */
> >   		ovl_copyattr(ovl_inode_real(inode), inode);
> > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > index fd47deea7c17..647c35423545 100644
> > --- a/include/linux/fs.h
> > +++ b/include/linux/fs.h
> > @@ -3275,6 +3275,11 @@ static inline int kiocb_set_rw_flags(struct kiocb *ki, rwf_t flags)
> >   	return 0;
> >   }
> >   
> > +static inline rwf_t iocb_to_rw_flags(int ifl, int iocb_mask)
> > +{
> > +	return ifl & iocb_mask;
> > +}
> > +
> >   static inline ino_t parent_ino(struct dentry *dentry)
> >   {
> >   	ino_t res;
> > --
> > 2.30.0.280.ga3ce27912f-goog
>
> For some reason lkml.org and lore.kernel.org are not showing this change
> as part of the thread.
> Let's see if replying to the email fixes the indexing.
>
> Regards,
> Alessio

Hi, Alessio

This change imply IOCB_* and RWF_* flags are properly aligned, which is 
not true for kernel version 5.4/4.19/4.14. As the patch ("fs: align 
IOCB_* flags with RWF_* flags") is not back-ported to these stable 
kernel branches. The issue was found when applying these patches
to kernel-5.4(files open with passthrough enabled can't do append 
write). I think the issue exists in AOSP common kernel too.
Could you please fix this?

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ce71bfea207b4d7c21d36f24ec37618ffcea1da8

https://android-review.googlesource.com/c/kernel/common/+/1556243

Thanks
yanwu