kernel_optimize_test/include
Sage Weil b7ed78f565 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>
2011-03-21 00:40:29 -04:00
..
acpi PM: Remove CONFIG_PM_OPS 2011-03-15 00:43:15 +01:00
asm-generic introduce sys_syncfs to sync a single file system 2011-03-21 00:40:29 -04:00
crypto
drm Merge remote branch 'intel/drm-intel-next' of ../drm-next into drm-core-next 2011-03-14 14:15:13 +10:00
keys RxRPC: Fix v1 keys 2011-03-02 22:18:53 -08:00
linux introduce sys_syncfs to sync a single file system 2011-03-21 00:40:29 -04:00
math-emu
media
mtd
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6 2011-03-16 16:29:25 -07:00
pcmcia pcmcia: re-enable Zoomed Video support 2011-02-20 12:47:34 +01:00
rdma
rxrpc
scsi Merge git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6 2011-03-17 17:54:40 -07:00
sound Merge branch 'topic/misc' into for-linus 2011-03-18 07:39:08 +01:00
target [SCSI] target: Fix t_transport_aborted handling in LUN_RESET + active I/O shutdown 2011-02-28 11:23:32 -06:00
trace Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6 2011-03-18 10:46:37 -07:00
video fbdev: sh_mobile_lcdc: Add YUV framebuffer support 2011-03-16 17:27:10 +09:00
xen Merge branch 'stable/xen.pm.bug-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen 2011-03-17 18:37:42 -07:00
Kbuild