nvmet: use i_size_read() to set size for file-ns

Instead of calling vfs_getattr() use i_size_read() to read the size of
file so we can read the size of not only file type but also block type
with one call. This is needed to implement buffered_io support for the
NVMeOF block device backend.

We also change return type of function nvmet_file_ns_revalidate() from
int to void, since this function does not return any meaning value.
Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/target/io-cmd-file.c

@@ -14,16 +14,9 @@
 #define NVMET_MAX_MPOOL_BVEC		16
 #define NVMET_MIN_MPOOL_OBJ		16
 
-int nvmet_file_ns_revalidate(struct nvmet_ns *ns)
+void nvmet_file_ns_revalidate(struct nvmet_ns *ns)
 {
-	struct kstat stat;
-	int ret;
-
-	ret = vfs_getattr(&ns->file->f_path, &stat, STATX_SIZE,
-			  AT_STATX_FORCE_SYNC);
-	if (!ret)
-		ns->size = stat.size;
-	return ret;
+	ns->size = i_size_read(ns->file->f_mapping->host);
 }
 
 void nvmet_file_ns_disable(struct nvmet_ns *ns)
@@ -43,7 +36,7 @@ void nvmet_file_ns_disable(struct nvmet_ns *ns)
 int nvmet_file_ns_enable(struct nvmet_ns *ns)
 {
 	int flags = O_RDWR | O_LARGEFILE;
-	int ret;
+	int ret = 0;
 
 	if (!ns->buffered_io)
 		flags |= O_DIRECT;
@@ -57,9 +50,7 @@ int nvmet_file_ns_enable(struct nvmet_ns *ns)
 		return ret;
 	}
 
-	ret = nvmet_file_ns_revalidate(ns);
-	if (ret)
-		goto err;
+	nvmet_file_ns_revalidate(ns);
 
 	/*
 	 * i_blkbits can be greater than the universally accepted upper bound,

drivers/nvme/target/nvmet.h

@@ -541,7 +541,7 @@ u16 nvmet_bdev_flush(struct nvmet_req *req);
 u16 nvmet_file_flush(struct nvmet_req *req);
 void nvmet_ns_changed(struct nvmet_subsys *subsys, u32 nsid);
 void nvmet_bdev_ns_revalidate(struct nvmet_ns *ns);
-int nvmet_file_ns_revalidate(struct nvmet_ns *ns);
+void nvmet_file_ns_revalidate(struct nvmet_ns *ns);
 void nvmet_ns_revalidate(struct nvmet_ns *ns);
 u16 blk_to_nvme_status(struct nvmet_req *req, blk_status_t blk_sts);