vfs: Provide S_KERNEL_FILE inode flag

Provide an S_KERNEL_FILE inode flag that a kernel service, e.g. cachefiles,
can set to ward off other kernel services and drivers (including itself)
from using files it is actively using.

Signed-off-by: David Howells <dhowells@redhat.com>

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 473ea3ff0ad4edcf8d8553590c9201dcdee916ca..d4ec20f51129ec78eb4ef94a1962149c29a6336e 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2249,6 +2249,7 @@ struct super_operations {
 #define S_ENCRYPTED    (1 << 14) /* Encrypted file (using fs/crypto/) */
 #define S_CASEFOLD     (1 << 15) /* Casefolded file */
 #define S_VERITY       (1 << 16) /* Verity file (using fs/verity/) */
+#define S_KERNEL_FILE  (1 << 17) /* File is in use by the kernel (eg. fs/cachefiles) */
 
 /*
  * Note that nosuid etc flags are inode-specific: setting some file-system