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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
..
9p fs/9p: Make the writeback_fid owned by root 2011-03-15 09:57:42 -05:00
adfs adfs: remove the big kernel lock 2011-03-02 00:02:38 +01:00
affs fs: change to new flag variable 2011-03-17 14:02:57 +01:00
afs afs: Fix oops in afs_unlink_writeback 2011-02-25 11:12:37 -08:00
autofs4 lose 'mounting_here' argument in ->d_manage() 2011-03-18 10:01:59 -04:00
befs befs: don't pass huge structs by value 2011-01-13 08:03:15 -08:00
bfs fs: icache RCU free inodes 2011-01-07 17:50:26 +11:00
btrfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-03-18 10:37:40 -07:00
cachefiles CacheFiles: Add calls to path-based security hooks 2011-01-24 10:49:45 +11:00
ceph ceph: fix d_revalidate oopsen on NFS exports 2011-03-10 03:44:05 -05:00
cifs [CIFS] update cifs version 2011-02-21 22:31:47 +00:00
coda fs: change to new flag variable 2011-03-17 14:02:57 +01:00
configfs configfs: change depends -> select SYSFS 2011-01-16 21:22:29 +00:00
cramfs cramfs: generate unique inode number for better inode cache usage 2011-01-13 08:03:23 -08:00
debugfs debugfs: Fix filesystem reference counting on debugfs_remove() failure 2011-02-18 08:07:18 -08:00
devpts
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dlm dlm: use alloc_workqueue function 2011-03-10 13:22:34 -06:00
ecryptfs eCryptfs: Copy up lower inode attrs in getattr 2011-02-21 14:46:36 -06:00
efs fs: icache RCU free inodes 2011-01-07 17:50:26 +11:00
exofs exofs: i_nlink races in rename() 2011-03-03 01:28:17 -05:00
exportfs vfs: Add open by file handle support 2011-03-15 02:21:44 -04:00
ext2 Merge branch 'master' of git://git.infradead.org/users/eparis/selinux into next 2011-03-08 11:38:10 +11:00
ext3 Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs-2.6 2011-03-17 17:41:19 -07:00
ext4 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-03-18 10:37:40 -07:00
fat exportfs: Return the minimum required handle size 2011-03-14 09:15:28 -04:00
freevxfs fs: icache RCU free inodes 2011-01-07 17:50:26 +11:00
fscache FS-Cache: Fix operation handling 2011-01-14 09:23:36 -08:00
fuse Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-03-18 10:37:40 -07:00
gfs2 Merge branch 'trivial' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6 2011-03-20 18:14:55 -07:00
hfs hfs: fix rename() over non-empty directory 2011-03-03 01:28:40 -05:00
hfsplus hfsplus: fix up a comparism in hfsplus_file_extend 2011-02-03 16:34:18 -07:00
hostfs switch hostfs 2011-01-12 20:03:42 -05:00
hpfs hpfs: remove the BKL 2011-03-02 22:27:36 +01:00
hppfs fs: icache RCU free inodes 2011-01-07 17:50:26 +11:00
hugetlbfs fs: icache RCU free inodes 2011-01-07 17:50:26 +11:00
isofs exportfs: Return the minimum required handle size 2011-03-14 09:15:28 -04:00
jbd jbd: Remove one to many n's in a word. 2011-02-28 21:55:58 +01:00
jbd2 jbd: Remove one to many n's in a word. 2011-02-28 21:55:58 +01:00
jffs2 Merge branch 'master' of git://git.infradead.org/users/eparis/selinux into next 2011-03-08 11:38:10 +11:00
jfs Merge branch 'trivial' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6 2011-03-20 18:14:55 -07:00
lockd NLM: Fix "kernel BUG at fs/lockd/host.c:417!" or ".../host.c:283!" 2011-01-25 15:24:47 -05:00
logfs Merge branch 'for-2.6.38/core' of git://git.kernel.dk/linux-2.6-block 2011-01-13 10:45:01 -08:00
minix minix: i_nlink races in rename() 2011-03-03 01:28:16 -05:00
ncpfs fs: change to new flag variable 2011-03-17 14:02:57 +01:00
nfs Merge branch 'nfs-for-2.6.39' of git://git.linux-nfs.org/projects/trondmy/nfs-2.6 2011-03-17 17:40:00 -07:00
nfs_common NFS: Prevent memory allocation failure in nfsacl_encode() 2011-01-25 15:24:47 -05:00
nfsd don't pass 'mounting_here' flag to follow_down() 2011-03-18 09:04:20 -04:00
nilfs2 nilfs2: get rid of nilfs_sb_info structure 2011-03-09 11:54:26 +09:00
nls
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notify Remove one to many n's in a word 2011-03-01 15:47:58 +01:00
ntfs fs: change to new flag variable 2011-03-17 14:02:57 +01:00
ocfs2 Merge branch 'trivial' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6 2011-03-20 18:14:55 -07:00
omfs omfs: make readdir stop when filldir says so 2011-03-05 16:24:12 -05:00
openpromfs fs: icache RCU free inodes 2011-01-07 17:50:26 +11:00
partitions Increase OSF partition limit from 8 to 18 2011-03-16 08:04:07 -07:00
proc Merge branch 'next' into for-linus 2011-03-16 09:41:17 +11:00
pstore Some fixes for pstore 2011-03-17 22:08:13 -04:00
qnx4 fs: icache RCU free inodes 2011-01-07 17:50:26 +11:00
quota quota: return -ENOMEM when memory allocation fails 2011-02-24 11:42:44 +01:00
ramfs
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reiserfs Merge branch 'trivial' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6 2011-03-20 18:14:55 -07:00
romfs fs: icache RCU free inodes 2011-01-07 17:50:26 +11:00
squashfs squashfs: fix use of uninitialised variable in zlib & xz decompressors 2011-01-26 10:50:05 +10:00
sysfs kconfig: rename CONFIG_EMBEDDED to CONFIG_EXPERT 2011-01-20 17:02:05 -08:00
sysv sysv: i_nlink races in rename() 2011-03-03 01:28:16 -05:00
ubifs Merge branch 'linux-next' of git://git.infradead.org/ubifs-2.6 2011-03-18 10:50:27 -07:00
udf Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-udf-2.6 2011-03-17 17:29:38 -07:00
ufs Merge branch 'config' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/bkl 2011-03-16 17:21:00 -07:00
xfs Merge branch 'trivial' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6 2011-03-20 18:14:55 -07:00
Kconfig Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-2.6 2011-03-16 19:01:29 -07:00
Kconfig.binfmt
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Makefile Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-2.6 2011-03-16 19:01:29 -07:00
aio.c Merge branch 'for-2.6.39' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2011-03-16 08:20:19 -07:00
anon_inodes.c sanitize vfsmount refcounting changes 2011-01-16 13:47:07 -05:00
attr.c
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bad_inode.c fs: provide rcu-walk aware permission i_ops 2011-01-07 17:50:29 +11:00
binfmt_aout.c
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binfmt_elf.c binfmt_elf: cleanups 2011-01-13 08:03:12 -08:00
binfmt_elf_fdpic.c
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binfmt_em86.c
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binfmt_flat.c
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binfmt_misc.c
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binfmt_script.c
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binfmt_som.c
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bio-integrity.c bio-integrity: mark kintegrityd_wq highpri and CPU intensive 2011-01-03 15:01:48 +01:00
bio.c bio: take care not overflow page count when mapping/copying user data 2010-11-10 14:40:43 +01:00
block_dev.c fs/block_dev.c: fix new kernel-doc warning 2011-02-28 18:08:31 -08:00
buffer.c fs: Use this_cpu_inc_return in buffer.c 2010-12-17 15:18:05 +01:00
char_dev.c Merge branch 'for-2.6.38/core' of git://git.kernel.dk/linux-2.6-block 2011-01-13 10:45:01 -08:00
compat.c select: remove unused MAX_SELECT_SECONDS 2011-03-21 00:16:08 -04:00
compat_binfmt_elf.c
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compat_ioctl.c Merge branch 'tty-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty-2.6 2011-01-07 14:39:20 -08:00
dcache.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2011-03-18 10:51:11 -07:00
dcookies.c
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direct-io.c Merge branch 'master' into for-next 2011-02-15 10:24:31 +01:00
drop_caches.c
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eventfd.c Docbook: add fs/eventfd.c and fix typos in it 2011-02-21 15:07:04 -08:00
eventpoll.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-03-18 10:37:40 -07:00
exec.c Small typo fix... 2011-03-21 00:16:09 -04:00
fcntl.c New kind of open files - "location only". 2011-03-15 02:21:45 -04:00
fhandle.c vfs: Add open by file handle support 2011-03-15 02:21:44 -04:00
fifo.c Filesystem: fifo: Fixed coding style issue. 2011-03-21 00:16:09 -04:00
file.c
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file_table.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2011-03-16 13:26:17 -07:00
filesystems.c fs: rcu-walk for path lookup 2011-01-07 17:50:27 +11:00
fs-writeback.c fs/fs-writeback.c: fix sync_inodes_sb() return value kernel-doc 2011-01-13 17:32:48 -08:00
fs_struct.c sanitize vfsmount refcounting changes 2011-01-16 13:47:07 -05:00
generic_acl.c fs: provide simple rcu-walk generic_check_acl implementation 2011-01-07 17:50:29 +11:00
inode.c fs/inode: Fix kernel-doc format for inode_init_owner 2011-03-21 00:16:08 -04:00
internal.h vfs: split off vfsmount-related parts of vfs_kern_mount() 2011-03-17 22:10:41 -04:00
ioctl.c vfs: cleanup do_vfs_ioctl() 2011-03-21 00:16:08 -04:00
ioprio.c ioprio: grab rcu_read_lock in sys_ioprio_{set,get}() 2010-11-15 10:23:31 +01:00
libfs.c pass default dentry_operations to mount_pseudo() 2011-01-12 20:03:43 -05:00
locks.c fs/locks.c: Remove stale FIXME left over from BKL conversion 2011-03-05 10:55:59 +01:00
mbcache.c ext2: Resolve 'dereferencing pointer to incomplete type' when enabling EXT2_XATTR_DEBUG 2011-01-10 19:04:08 +01:00
mpage.c fs/mpage.c: consolidate code 2011-01-13 17:32:32 -08:00
namei.c lose 'mounting_here' argument in ->d_manage() 2011-03-18 10:01:59 -04:00
namespace.c change the locking order for namespace_sem 2011-03-18 08:55:38 -04:00
nfsctl.c open-style analog of vfs_path_lookup() 2011-03-14 09:15:28 -04:00
no-block.c
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open.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/security-testing-2.6 2011-03-16 09:15:43 -07:00
pipe.c Fix broken "pipe: use event aware wakeups" optimization 2011-01-20 16:21:59 -08:00
pnode.c fs: scale mntget/mntput 2011-01-07 17:50:33 +11:00
pnode.h
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posix_acl.c NFS: Prevent memory allocation failure in nfsacl_encode() 2011-01-25 15:24:47 -05:00
read_write.c fix signedness mess in rw_verify_area() on 64bit architectures 2011-01-12 20:06:58 -05:00
read_write.h
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readdir.c
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select.c select: remove unused MAX_SELECT_SECONDS 2011-03-21 00:16:08 -04:00
seq_file.c
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signalfd.c
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splice.c Merge branch 'for-2.6.38/core' of git://git.kernel.dk/linux-2.6-block 2011-01-13 10:45:01 -08:00
stack.c
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stat.c readlinkat(), fchownat() and fstatat() with empty relative pathnames 2011-03-15 02:21:45 -04:00
statfs.c clean statfs-like syscalls up 2011-03-14 09:15:28 -04:00
super.c vfs: split off vfsmount-related parts of vfs_kern_mount() 2011-03-17 22:10:41 -04:00
sync.c introduce sys_syncfs to sync a single file system 2011-03-21 00:40:29 -04:00
timerfd.c
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utimes.c
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xattr.c
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xattr_acl.c
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