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authorSage Weil <sage@newdream.net>2011-03-10 11:31:30 -0800
committerAl Viro <viro@zeniv.linux.org.uk>2011-03-21 00:40:29 -0400
commitb7ed78f56575074f29ec99d8984f347f6c99c914 (patch)
tree7bc901458a9f47b197052e98a25c4a4f10c52607 /include/asm-generic
parent1bef82917c74249ff21982127e57defd6ca2bb1b (diff)
introduce sys_syncfs to sync a single file system
It is frequently useful to sync a single file system, instead of all mounted file systems via sync(2): - On machines with many mounts, it is not at all uncommon for some of them to hang (e.g. unresponsive NFS server). sync(2) will get stuck on those and may never get to the one you do care about (e.g., /). - Some applications write lots of data to the file system and then want to make sure it is flushed to disk. Calling fsync(2) on each file introduces unnecessary ordering constraints that result in a large amount of sub-optimal writeback/flush/commit behavior by the file system. There are currently two ways (that I know of) to sync a single super_block: - BLKFLSBUF ioctl on the block device: That also invalidates the bdev mapping, which isn't usually desirable, and doesn't work for non-block file systems. - 'mount -o remount,rw' will call sync_filesystem as an artifact of the current implemention. Relying on this little-known side effect for something like data safety sounds foolish. Both of these approaches require root privileges, which some applications do not have (nor should they need?) given that sync(2) is an unprivileged operation. This patch introduces a new system call syncfs(2) that takes an fd and syncs only the file system it references. Maybe someday we can $ sync /some/path and not get sync: ignoring all arguments The syscall is motivated by comments by Al and Christoph at the last LSF. syncfs(2) seems like an appropriate name given statfs(2). A similar ioctl was also proposed a while back, see http://marc.info/?l=linux-fsdevel&m=127970513829285&w=2 Signed-off-by: Sage Weil <sage@newdream.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'include/asm-generic')
-rw-r--r--include/asm-generic/unistd.h4
1 files changed, 3 insertions, 1 deletions
diff --git a/include/asm-generic/unistd.h b/include/asm-generic/unistd.h
index d94f447c667a..176b825add52 100644
--- a/include/asm-generic/unistd.h
+++ b/include/asm-generic/unistd.h
@@ -652,9 +652,11 @@ __SYSCALL(__NR_name_to_handle_at, sys_name_to_handle_at)
__SYSCALL(__NR_open_by_handle_at, sys_open_by_handle_at)
#define __NR_clock_adjtime 266
__SYSCALL(__NR_clock_adjtime, sys_clock_adjtime)
+#define __NR_syncfs 264
+__SYSCALL(__NR_syncfs, sys_syncfs)
#undef __NR_syscalls
-#define __NR_syscalls 267
+#define __NR_syscalls 268
/*
* All syscalls below here should go away really,