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authorJens Axboe <axboe@kernel.dk>2017-06-27 20:47:04 +0300
committerJens Axboe <axboe@kernel.dk>2017-06-27 21:05:22 +0300
commitc75b1d9421f80f4143e389d2d50ddfc8a28c8c35 (patch)
tree6fe665d5e9f8cfab50b764d418e732617a5d5129 /include/uapi
parent12e9a6d62236dacb87a6b2dd84dd9c29bb5be1de (diff)
downloadlinux-c75b1d9421f80f4143e389d2d50ddfc8a28c8c35.tar.xz
fs: add fcntl() interface for setting/getting write life time hints
Define a set of write life time hints: RWH_WRITE_LIFE_NOT_SET No hint information set RWH_WRITE_LIFE_NONE No hints about write life time RWH_WRITE_LIFE_SHORT Data written has a short life time RWH_WRITE_LIFE_MEDIUM Data written has a medium life time RWH_WRITE_LIFE_LONG Data written has a long life time RWH_WRITE_LIFE_EXTREME Data written has an extremely long life time The intent is for these values to be relative to each other, no absolute meaning should be attached to these flag names. Add an fcntl interface for querying these flags, and also for setting them as well: F_GET_RW_HINT Returns the read/write hint set on the underlying inode. F_SET_RW_HINT Set one of the above write hints on the underlying inode. F_GET_FILE_RW_HINT Returns the read/write hint set on the file descriptor. F_SET_FILE_RW_HINT Set one of the above write hints on the file descriptor. The user passes in a 64-bit pointer to get/set these values, and the interface returns 0/-1 on success/error. Sample program testing/implementing basic setting/getting of write hints is below. Add support for storing the write life time hint in the inode flags and in struct file as well, and pass them to the kiocb flags. If both a file and its corresponding inode has a write hint, then we use the one in the file, if available. The file hint can be used for sync/direct IO, for buffered writeback only the inode hint is available. This is in preparation for utilizing these hints in the block layer, to guide on-media data placement. /* * writehint.c: get or set an inode write hint */ #include <stdio.h> #include <fcntl.h> #include <stdlib.h> #include <unistd.h> #include <stdbool.h> #include <inttypes.h> #ifndef F_GET_RW_HINT #define F_LINUX_SPECIFIC_BASE 1024 #define F_GET_RW_HINT (F_LINUX_SPECIFIC_BASE + 11) #define F_SET_RW_HINT (F_LINUX_SPECIFIC_BASE + 12) #endif static char *str[] = { "RWF_WRITE_LIFE_NOT_SET", "RWH_WRITE_LIFE_NONE", "RWH_WRITE_LIFE_SHORT", "RWH_WRITE_LIFE_MEDIUM", "RWH_WRITE_LIFE_LONG", "RWH_WRITE_LIFE_EXTREME" }; int main(int argc, char *argv[]) { uint64_t hint; int fd, ret; if (argc < 2) { fprintf(stderr, "%s: file <hint>\n", argv[0]); return 1; } fd = open(argv[1], O_RDONLY); if (fd < 0) { perror("open"); return 2; } if (argc > 2) { hint = atoi(argv[2]); ret = fcntl(fd, F_SET_RW_HINT, &hint); if (ret < 0) { perror("fcntl: F_SET_RW_HINT"); return 4; } } ret = fcntl(fd, F_GET_RW_HINT, &hint); if (ret < 0) { perror("fcntl: F_GET_RW_HINT"); return 3; } printf("%s: hint %s\n", argv[1], str[hint]); close(fd); return 0; } Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'include/uapi')
-rw-r--r--include/uapi/linux/fcntl.h21
1 files changed, 21 insertions, 0 deletions
diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h
index 813afd6eee71..ec69d55bcec7 100644
--- a/include/uapi/linux/fcntl.h
+++ b/include/uapi/linux/fcntl.h
@@ -43,6 +43,27 @@
/* (1U << 31) is reserved for signed error codes */
/*
+ * Set/Get write life time hints. {GET,SET}_RW_HINT operate on the
+ * underlying inode, while {GET,SET}_FILE_RW_HINT operate only on
+ * the specific file.
+ */
+#define F_GET_RW_HINT (F_LINUX_SPECIFIC_BASE + 11)
+#define F_SET_RW_HINT (F_LINUX_SPECIFIC_BASE + 12)
+#define F_GET_FILE_RW_HINT (F_LINUX_SPECIFIC_BASE + 13)
+#define F_SET_FILE_RW_HINT (F_LINUX_SPECIFIC_BASE + 14)
+
+/*
+ * Valid hint values for F_{GET,SET}_RW_HINT. 0 is "not set", or can be
+ * used to clear any hints previously set.
+ */
+#define RWF_WRITE_LIFE_NOT_SET 0
+#define RWH_WRITE_LIFE_NONE 1
+#define RWH_WRITE_LIFE_SHORT 2
+#define RWH_WRITE_LIFE_MEDIUM 3
+#define RWH_WRITE_LIFE_LONG 4
+#define RWH_WRITE_LIFE_EXTREME 5
+
+/*
* Types of directory notifications that may be requested.
*/
#define DN_ACCESS 0x00000001 /* File accessed */