In barebox, the dirty block cache for a given device is flushed when
closing all file descriptors to it, a cached block needs to be evicted
due to pressure or when barebox shuts down.
There are valid uses to do it explicitly however:
- When benchmarking write speed to a block device
- Before forced resets, because a regular reset would run shutdown
code that should be omitted.
Add a sync command that does this. Unlike the userspace variant, we
don't bother to implement a argument-less sync that's global. Users are
supposed to flush the files they are actually interested in, e.g.:
sync /dev/mmc2.0
Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
---
v1 -> v2:
- fix typo in commit message (Sascha)
---
commands/Kconfig | 14 ++++++++++++++
commands/Makefile | 1 +
commands/sync.c | 42 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 57 insertions(+)
create mode 100644 commands/sync.c
diff --git a/commands/Kconfig b/commands/Kconfig
index 5b512f1bbac7..a8b7037618cc 100644
--- a/commands/Kconfig
+++ b/commands/Kconfig
@@ -1871,6 +1871,20 @@ config CMD_DETECT
-e bail out if one device fails to detect
-a detect all devices
+config CMD_SYNC
+ tristate
+ prompt "sync"
+ help
+ sync - flush cached writes
+
+ Usage: sync DEVICE
+
+ Synchronize cached writes to persistent storage of DEVICE
+ immediately instead of waiting for block device to be closed,
+ cache eviction or the regular barebox exit.
+
+ This command is mainly useful for benchmarking.
+
config CMD_FLASH
tristate
prompt "erase, protect and unprotect"
diff --git a/commands/Makefile b/commands/Makefile
index 4ca7ba7eb609..a9dbead4389f 100644
--- a/commands/Makefile
+++ b/commands/Makefile
@@ -41,6 +41,7 @@ obj-$(CONFIG_CMD_REGINFO) += reginfo.o
obj-$(CONFIG_CMD_CRC) += crc.o
obj-$(CONFIG_CMD_CLEAR) += clear.o
obj-$(CONFIG_CMD_TEST) += test.o
+obj-$(CONFIG_CMD_SYNC) += sync.o
obj-$(CONFIG_CMD_FLASH) += flash.o
obj-$(CONFIG_CMD_MEMINFO) += meminfo.o
obj-$(CONFIG_CMD_TIMEOUT) += timeout.o
diff --git a/commands/sync.c b/commands/sync.c
new file mode 100644
index 000000000000..6add67cd0876
--- /dev/null
+++ b/commands/sync.c
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+/* sync - flushing support */
+
+#include <common.h>
+#include <command.h>
+#include <fcntl.h>
+#include <fs.h>
+
+static int do_sync(int argc, char *argv[])
+{
+ int ret, fd;
+
+ if (argc != 2)
+ return COMMAND_ERROR_USAGE;
+
+ fd = open(argv[1], O_WRONLY);
+ if (fd < 0) {
+ printf("open %s: %m\n", argv[1]);
+ return 1;
+ }
+
+ ret = flush(fd);
+
+ close(fd);
+
+ return ret;
+}
+
+BAREBOX_CMD_HELP_START(sync)
+BAREBOX_CMD_HELP_TEXT("Synchronize cached writes to persistent storage of DEVICE")
+BAREBOX_CMD_HELP_TEXT("immediately instead of waiting for block device to be closed,")
+BAREBOX_CMD_HELP_TEXT("cache eviction or the regular barebox exit.")
+BAREBOX_CMD_HELP_END
+
+BAREBOX_CMD_START(sync)
+ .cmd = do_sync,
+ BAREBOX_CMD_DESC("flush cached writes")
+ BAREBOX_CMD_OPTS("DEVICE")
+ BAREBOX_CMD_GROUP(CMD_GRP_HWMANIP)
+ BAREBOX_CMD_HELP(cmd_sync_help)
+BAREBOX_CMD_END
--
2.39.2
