fs: move the bdex_statx call to vfs_getattr_nosec

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: 2d985f8 ("vfs: support STATX_DIOALIGN on block devices")
Fixes: f4774e9 ("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>
Link: https://lore.kernel.org/20250417064042.712140-1-hch@lst.de
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Christoph Hellwig

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;

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;
 }
 

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)