Re: [PATCH] fuse: invalidate the page cache after direct write

[Bernd Schubert <bernd@bsbernd.com>]

Hi Jingbo,

thanks a lot, I have an internal ticket assigned for that, but never
found the time to look into it.

On 1/6/26 08:52, Jingbo Xu wrote:
> This fixes xfstests generic/451 (for both O_DIRECT and FOPEN_DIRECT_IO
> direct write).
> 
> Commit b359af8275a9 ("fuse: Invalidate the page cache after
> FOPEN_DIRECT_IO write") tries to fix the similar issue for
> FOPEN_DIRECT_IO write, which can be reproduced by xfstests generic/209.
> It only fixes the issue for synchronous direct write, while omitting
> the case for asynchronous direct write (exactly targeted by
> generic/451).
> 
> While for O_DIRECT direct write, it's somewhat more complicated.  For
> synchronous direct write, generic_file_direct_write() will invalidate
> the page cache after the write, and thus it can pass generic/209.  While
> for asynchronous direct write, the invalidation in
> generic_file_direct_write() is bypassed since the invalidation shall be
> done when the asynchronous IO completes.  This is omitted in FUSE and
> generic/451 fails whereby.
> 
> Fix this by conveying the invalidation in both sync and async
> (FUSE_ASYNC_DIO) request submission.  The only side effect is that
> there's a redundant invalidation for synchronous direct write when
> FUSE_ASYNC_DIO is disabled (in fuse_send_write()), given the same
> range has been invalidated once in generic_file_direct_write().

The side effect should only come without FOPEN_DIRECT_IO. Could you add
this diff to avoid it?

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index d6ae3b4652f8..c04296316a82 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1177,7 +1177,13 @@ static ssize_t fuse_send_write(struct fuse_io_args *ia, loff_t pos,
        written = ia->write.out.size;
        if (!err && written > count)
                err = -EIO;
-       if (!err && written && mapping->nrpages) {
+
+       /*
+        * without FOPEN_DIRECT_IO generic_file_direct_write() does the
+        * invalidation for us
+        */
+       if (!err && written && mapping->nrpages &&
+           (ff->open_flags & FOPEN_DIRECT_IO)) {
                /*
                 * As in generic_file_direct_write(), invalidate after the
                 * write, to invalidate read-ahead cache that may have competed


> 
> Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
> ---
>  fs/fuse/file.c | 37 ++++++++++++++++++++++++++-----------
>  1 file changed, 26 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 01bc894e9c2b..d6ae3b4652f8 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -667,6 +667,18 @@ static void fuse_aio_complete(struct fuse_io_priv *io, int err, ssize_t pos)
>  			struct inode *inode = file_inode(io->iocb->ki_filp);
>  			struct fuse_conn *fc = get_fuse_conn(inode);
>  			struct fuse_inode *fi = get_fuse_inode(inode);
> +			struct address_space *mapping = io->iocb->ki_filp->f_mapping;
> +
> +			/*
> +			 * As in generic_file_direct_write(), invalidate after the
> +			 * write, to invalidate read-ahead cache that may have competed
> +			 * with the write.
> +			 */
> +			if (io->write && res && mapping->nrpages) {
> +				invalidate_inode_pages2_range(mapping,
> +						io->offset >> PAGE_SHIFT,
> +						(io->offset + res - 1) >> PAGE_SHIFT);
> +			}
>  
>  			spin_lock(&fi->lock);
>  			fi->attr_version = atomic64_inc_return(&fc->attr_version);
> @@ -1144,9 +1156,11 @@ static ssize_t fuse_send_write(struct fuse_io_args *ia, loff_t pos,
>  {
>  	struct kiocb *iocb = ia->io->iocb;
>  	struct file *file = iocb->ki_filp;
> +	struct address_space *mapping = file->f_mapping;
>  	struct fuse_file *ff = file->private_data;
>  	struct fuse_mount *fm = ff->fm;
>  	struct fuse_write_in *inarg = &ia->write.in;
> +	ssize_t written;
>  	ssize_t err;
>  
>  	fuse_write_args_fill(ia, ff, pos, count);
> @@ -1160,10 +1174,20 @@ static ssize_t fuse_send_write(struct fuse_io_args *ia, loff_t pos,
>  		return fuse_async_req_send(fm, ia, count);
>  
>  	err = fuse_simple_request(fm, &ia->ap.args);
> -	if (!err && ia->write.out.size > count)
> +	written = ia->write.out.size;
> +	if (!err && written > count)
>  		err = -EIO;
> +	if (!err && written && mapping->nrpages) {
> +		/*
> +		 * As in generic_file_direct_write(), invalidate after the
> +		 * write, to invalidate read-ahead cache that may have competed
> +		 * with the write.
> +		 */
> +		invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT,
> +					(pos + written - 1) >> PAGE_SHIFT);
> +	}
>  
> -	return err ?: ia->write.out.size;
> +	return err ?: written;
>  }
>  
>  bool fuse_write_update_attr(struct inode *inode, loff_t pos, ssize_t written)
> @@ -1738,15 +1762,6 @@ ssize_t fuse_direct_io(struct fuse_io_priv *io, struct iov_iter *iter,
>  	if (res > 0)
>  		*ppos = pos;
>  
> -	if (res > 0 && write && fopen_direct_io) {
> -		/*
> -		 * As in generic_file_direct_write(), invalidate after the
> -		 * write, to invalidate read-ahead cache that may have competed
> -		 * with the write.
> -		 */
> -		invalidate_inode_pages2_range(mapping, idx_from, idx_to);
> -	}
> -
>  	return res > 0 ? res : err;
>  }
>  EXPORT_SYMBOL_GPL(fuse_direct_io);

Assuming you apply the diff above, feel free to add for v2
Reviewed-by: Bernd Schubert <bschubert@ddn.com>


Thanks,
Bernd