aufs: fhsm (file-based hierarchical storage management)

This feature automatically handles MVDOWN in other commits.
In user-space, a daemon monitors the free space of the branch and issues
MVDOWN ioctl automatically when necessary. The main role is in
user-space and several options are implemented.
For a branch to join the FHSM circle, a new attribute 'fhsm' should be
specified.

See also the document in this commit.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

include/uapi/linux/aufs_type.h

@@ -81,6 +81,7 @@ typedef int16_t aufs_bindex_t;
 #define AUFS_WKQ_NAME		AUFS_NAME "d"
 #define AUFS_MFS_DEF_SEC	30 /* seconds */
 #define AUFS_MFS_MAX_SEC	3600 /* seconds */
+#define AUFS_FHSM_CACHE_DEF_SEC	30 /* seconds */
 #define AUFS_PLINK_WARN		50 /* number of plinks in a single bucket */
 
 /* pseudo-link maintenace under /proc */
@@ -113,6 +114,7 @@ typedef int16_t aufs_bindex_t;
 #define AUFS_BRPERM_RR		"rr"
 #define AUFS_BRATTR_COO_REG	"coo_reg"
 #define AUFS_BRATTR_COO_ALL	"coo_all"
+#define AUFS_BRATTR_FHSM	"fhsm"
 #define AUFS_BRATTR_ICEX	"icex"
 #define AUFS_BRATTR_ICEX_SEC	"icexsec"
 #define AUFS_BRATTR_ICEX_SYS	"icexsys"
@@ -132,6 +134,8 @@ typedef int16_t aufs_bindex_t;
 #define AuBrAttr_COO_ALL	(1 << 4)
 #define AuBrAttr_COO_Mask	(AuBrAttr_COO_REG | AuBrAttr_COO_ALL)
 
+#define AuBrAttr_FHSM		(1 << 5)	/* file-based hsm */
+
 /* ignore error in copying XATTR */
 #define AuBrAttr_ICEX_SEC	(1 << 7)
 #define AuBrAttr_ICEX_SYS	(1 << 8)
@@ -155,6 +159,10 @@ typedef int16_t aufs_bindex_t;
 
 /* #warning test userspace */
 #ifdef __KERNEL__
+#ifndef CONFIG_AUFS_FHSM
+#undef AuBrAttr_FHSM
+#define AuBrAttr_FHSM		0
+#endif
 #ifndef CONFIG_AUFS_XATTR
 #undef	AuBrAttr_ICEX
 #define AuBrAttr_ICEX		0
@@ -174,6 +182,8 @@ typedef int16_t aufs_bindex_t;
 /* the longest combination */
 /* AUFS_BRATTR_ICEX and AUFS_BRATTR_ICEX_TR don't affect here */
 #define AuBrPermStrSz	sizeof(AUFS_BRPERM_RW			\
+			       "+" AUFS_BRATTR_COO_REG		\
+			       "+" AUFS_BRATTR_FHSM		\
 			       "+" AUFS_BRATTR_ICEX_SEC		\
 			       "+" AUFS_BRATTR_ICEX_SYS		\
 			       "+" AUFS_BRATTR_ICEX_USR		\
@@ -204,6 +214,11 @@ static inline int au_br_cmoo(int brperm)
 	return brperm & AuBrAttr_CMOO_Mask;
 }
 
+static inline int au_br_fhsm(int brperm)
+{
+	return brperm & AuBrAttr_FHSM;
+}
+
 /* ---------------------------------------------------------------------- */
 
 /* ioctl */
@@ -215,7 +230,8 @@ enum {
 	AuCtl_WBR_FD,	/* pathconf wrapper */
 	AuCtl_IBUSY,	/* busy inode */
 	AuCtl_MVDOWN,	/* move-down */
-	AuCtl_BR	/* info about branches */
+	AuCtl_BR,	/* info about branches */
+	AuCtl_FHSM_FD	/* connection for fhsm */
 };
 
 /* borrowed from linux/include/linux/kernel.h */
@@ -409,5 +425,6 @@ union aufs_brinfo {
 #define AUFS_CTL_MVDOWN		_IOWR(AuCtlType, AuCtl_MVDOWN, \
 				      struct aufs_mvdown)
 #define AUFS_CTL_BRINFO		_IOW(AuCtlType, AuCtl_BR, union aufs_brinfo)
+#define AUFS_CTL_FHSM_FD	_IOW(AuCtlType, AuCtl_FHSM_FD, int)
 
 #endif /* __AUFS_TYPE_H__ */