Re: [PATCH] fs: move the bdex_statx call to vfs_getattr_nosec

["Darrick J. Wong" <djwong@kernel.org>]

On Thu, Apr 17, 2025 at 08:40:42AM +0200, Christoph Hellwig wrote:
> Currently bdex_statx is only called from the very high-level
> vfs_statx_path function, and thus bypassing it for in-kernel calls
> to vfs_getattr or vfs_getattr_nosec.
> 
> This breaks querying the block ѕize of the underlying device in the
> loop driver and also is a pitfall for any other new kernel caller.
> 
> Move the call into the lowest level helper to ensure all callers get
> the right results.
> 
> Fixes: 2d985f8c6b91 ("vfs: support STATX_DIOALIGN on block devices")
> Fixes: f4774e92aab8 ("loop: take the file system minimum dio alignment into account")
> Reported-by: Darrick J. Wong <djwong@kernel.org>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

This appears to solve the problem as well.

Tested-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  block/bdev.c           |  3 +--
>  fs/stat.c              | 32 ++++++++++++++++++--------------
>  include/linux/blkdev.h |  6 +++---
>  3 files changed, 22 insertions(+), 19 deletions(-)
> 
> diff --git a/block/bdev.c b/block/bdev.c
> index 4844d1e27b6f..6a34179192c9 100644
> --- a/block/bdev.c
> +++ b/block/bdev.c
> @@ -1272,8 +1272,7 @@ void sync_bdevs(bool wait)
>  /*
>   * Handle STATX_{DIOALIGN, WRITE_ATOMIC} for block devices.
>   */
> -void bdev_statx(struct path *path, struct kstat *stat,
> -		u32 request_mask)
> +void bdev_statx(const struct path *path, struct kstat *stat, u32 request_mask)
>  {
>  	struct inode *backing_inode;
>  	struct block_device *bdev;
> diff --git a/fs/stat.c b/fs/stat.c
> index f13308bfdc98..3d9222807214 100644
> --- a/fs/stat.c
> +++ b/fs/stat.c
> @@ -204,12 +204,25 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat,
>  				  STATX_ATTR_DAX);
>  
>  	idmap = mnt_idmap(path->mnt);
> -	if (inode->i_op->getattr)
> -		return inode->i_op->getattr(idmap, path, stat,
> -					    request_mask,
> -					    query_flags);
> +	if (inode->i_op->getattr) {
> +		int ret;
> +
> +		ret = inode->i_op->getattr(idmap, path, stat, request_mask,
> +				query_flags);
> +		if (ret)
> +			return ret;
> +	} else {
> +		generic_fillattr(idmap, request_mask, inode, stat);
> +	}
> +
> +	/*
> +	 * If this is a block device inode, override the filesystem attributes
> +	 * with the block device specific parameters that need to be obtained
> +	 * from the bdev backing inode.
> +	 */
> +	if (S_ISBLK(stat->mode))
> +		bdev_statx(path, stat, request_mask);
>  
> -	generic_fillattr(idmap, request_mask, inode, stat);
>  	return 0;
>  }
>  EXPORT_SYMBOL(vfs_getattr_nosec);
> @@ -295,15 +308,6 @@ static int vfs_statx_path(struct path *path, int flags, struct kstat *stat,
>  	if (path_mounted(path))
>  		stat->attributes |= STATX_ATTR_MOUNT_ROOT;
>  	stat->attributes_mask |= STATX_ATTR_MOUNT_ROOT;
> -
> -	/*
> -	 * If this is a block device inode, override the filesystem
> -	 * attributes with the block device specific parameters that need to be
> -	 * obtained from the bdev backing inode.
> -	 */
> -	if (S_ISBLK(stat->mode))
> -		bdev_statx(path, stat, request_mask);
> -
>  	return 0;
>  }
>  
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index e39c45bc0a97..678dc38442bf 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -1685,7 +1685,7 @@ int sync_blockdev(struct block_device *bdev);
>  int sync_blockdev_range(struct block_device *bdev, loff_t lstart, loff_t lend);
>  int sync_blockdev_nowait(struct block_device *bdev);
>  void sync_bdevs(bool wait);
> -void bdev_statx(struct path *, struct kstat *, u32);
> +void bdev_statx(const struct path *path, struct kstat *stat, u32 request_mask);
>  void printk_all_partitions(void);
>  int __init early_lookup_bdev(const char *pathname, dev_t *dev);
>  #else
> @@ -1703,8 +1703,8 @@ static inline int sync_blockdev_nowait(struct block_device *bdev)
>  static inline void sync_bdevs(bool wait)
>  {
>  }
> -static inline void bdev_statx(struct path *path, struct kstat *stat,
> -				u32 request_mask)
> +static inline void bdev_statx(const struct path *path, struct kstat *stat,
> +		u32 request_mask)
>  {
>  }
>  static inline void printk_all_partitions(void)
> -- 
> 2.47.2
> 
>