On Thu, 10 Mar 2011 11:31:30 -0800 (PST), Sage Weil <sage@xxxxxxxxxxxx> wrote: > 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@xxxxxxxxxxxx> Reviewed-by: Aneesh Kumar <aneesh.kumar@xxxxxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
