fs: introduce SB_INLINECRYPT

Introduce SB_INLINECRYPT, which is set by filesystems that wish to use
blk-crypto for file content en/decryption. This flag maps to the
'-o inlinecrypt' mount option which multiple filesystems will implement,
and code in fs/crypto/ needs to be able to check for this mount option
in a filesystem-independent way.

Signed-off-by: Satya Tangirala <[email protected]>
Reviewed-by: Jaegeuk Kim <[email protected]>
Reviewed-by: Eric Biggers <[email protected]>
Reviewed-by: Theodore Ts'o <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Eric Biggers <[email protected]>

Author: Satya Tangirala

include/linux/fs.h

@@ -1380,6 +1380,7 @@ extern int send_sigurg(struct fown_struct *fown);
 #define SB_NODIRATIME	2048	/* Do not update directory access times */
 #define SB_SILENT	32768
 #define SB_POSIXACL	(1<<16)	/* VFS does not apply the umask */
+#define SB_INLINECRYPT	(1<<17)	/* Use blk-crypto for encrypted files */
 #define SB_KERNMOUNT	(1<<22) /* this is a kern_mount call */
 #define SB_I_VERSION	(1<<23) /* Update inode I_version field */
 #define SB_LAZYTIME	(1<<25) /* Update the on-disk [acm]times lazily */