[PATCH v2 1/1] efivarfs: fix statfs() on efivarfs

[Heinrich Schuchardt]

Some firmware (notably U-Boot) provides GetVariable() and
GetNextVariableName() but not QueryVariableInfo().

With commit d86ff3333cb1 ("efivarfs: expose used and total size") the
statfs syscall was broken for such firmware.

If QueryVariableInfo() does not exist or returns an error, just report the
file-system size as 0 as statfs_simple() previously did.

Fixes: d86ff3333cb1 ("efivarfs: expose used and total size")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@xxxxxxxxxxxxx>
---
v2:
	initialize remaining_space to 0
---
 fs/efivarfs/super.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c
index e028fafa04f3..3893aae6a9be 100644
--- a/fs/efivarfs/super.c
+++ b/fs/efivarfs/super.c
@@ -29,14 +29,9 @@ static int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	const u32 attr = EFI_VARIABLE_NON_VOLATILE |
 			 EFI_VARIABLE_BOOTSERVICE_ACCESS |
 			 EFI_VARIABLE_RUNTIME_ACCESS;
-	u64 storage_space, remaining_space, max_variable_size;
+	u64 storage_space, remaining_space = 0, max_variable_size;
 	efi_status_t status;
 
-	status = efivar_query_variable_info(attr, &storage_space, &remaining_space,
-					    &max_variable_size);
-	if (status != EFI_SUCCESS)
-		return efi_status_to_err(status);
-
 	/*
 	 * This is not a normal filesystem, so no point in pretending it has a block
 	 * size; we declare f_bsize to 1, so that we can then report the exact value
@@ -44,10 +39,19 @@ static int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	 */
 	buf->f_bsize	= 1;
 	buf->f_namelen	= NAME_MAX;
-	buf->f_blocks	= storage_space;
-	buf->f_bfree	= remaining_space;
 	buf->f_type	= dentry->d_sb->s_magic;
 
+	/* Some UEFI firmware does not implement QueryVariable() */
+	if (efi_rt_services_supported(EFI_RT_SUPPORTED_QUERY_VARIABLE_INFO)) {
+		status = efivar_query_variable_info(attr, &storage_space,
+						    &remaining_space,
+						    &max_variable_size);
+		if (status == EFI_SUCCESS) {
+			buf->f_blocks	= storage_space;
+			buf->f_bfree	= remaining_space;
+		}
+	}
+
 	/*
 	 * In f_bavail we declare the free space that the kernel will allow writing
 	 * when the storage_paranoia x86 quirk is active. To use more, users
-- 
2.40.1