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0c28887493
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Vivek Goyal 0c28887493 ovl: A new xattr OVL_XATTR_METACOPY for file on upper 
Now we will have the capability to have upper inodes which might be only
metadata copy up and data is still on lower inode.  So add a new xattr
OVL_XATTR_METACOPY to distinguish between two cases.

Presence of OVL_XATTR_METACOPY reflects that file has been copied up
metadata only and and data will be copied up later from lower origin.  So
this xattr is set when a metadata copy takes place and cleared when data
copy takes place.

We also use a bit in ovl_inode->flags to cache OVL_UPPERDATA which reflects
whether ovl inode has data or not (as opposed to metadata only copy up).

If a file is copied up metadata only and later when same file is opened for
WRITE, then data copy up takes place.  We copy up data, remove METACOPY
xattr and then set the UPPERDATA flag in ovl_inode->flags.  While all these
operations happen with oi->lock held, read side of oi->flags can be
lockless.  That is another thread on another cpu can check if UPPERDATA
flag is set or not.

So this gives us an ordering requirement w.r.t UPPERDATA flag.  That is, if
another cpu sees UPPERDATA flag set, then it should be guaranteed that
effects of data copy up and remove xattr operations are also visible.

For example.

	CPU1				CPU2
ovl_open()				acquire(oi->lock)
 ovl_open_maybe_copy_up()                ovl_copy_up_data()
  open_open_need_copy_up()		 vfs_removexattr()
   ovl_already_copied_up()
    ovl_dentry_needs_data_copy_up()	 ovl_set_flag(OVL_UPPERDATA)
     ovl_test_flag(OVL_UPPERDATA)       release(oi->lock)

Say CPU2 is copying up data and in the end sets UPPERDATA flag.  But if
CPU1 perceives the effects of setting UPPERDATA flag but not the effects of
preceding operations (ex. upper that is not fully copied up), it will be a
problem.

Hence this patch introduces smp_wmb() on setting UPPERDATA flag operation
and smp_rmb() on UPPERDATA flag test operation.

May be some other lock or barrier is already covering it. But I am not sure
what that is and is it obvious enough that we will not break it in future.

So hence trying to be safe here and introducing barriers explicitly for
UPPERDATA flag/bit.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-07-20 09:56:08 +02:00
..
9p treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
adfs vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
affs affs: fix potential memory leak when parsing option 'prefix' 2018-05-28 12:36:41 +02:00
afs Merge branch 'afs-proc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-06-16 16:32:04 +09:00
autofs autofs: Fix typo s/thenew new/the new/ in AUTOFS4_FS description 2018-06-12 12:31:19 -07:00
befs fix a series of Documentation/ broken file name references 2018-06-15 18:10:01 -03:00
bfs bfs_add_entry: pass name/len as qstr pointer 2018-05-22 14:27:50 -04:00
btrfs vfs: dedupe: rationalize args 2018-07-06 23:57:03 +02:00
cachefiles Merge branch 'hch.procfs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-06-04 10:00:01 -07:00
ceph vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
cifs vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
coda vfs: change inode times to use struct timespec64 2018-06-05 16:57:31 -07:00
configfs vfs: change inode times to use struct timespec64 2018-06-05 16:57:31 -07:00
cramfs vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
crypto f2fs-for-4.18-rc1 2018-06-11 10:16:13 -07:00
debugfs Revert "debugfs: inode: debugfs_create_dir uses mode permission from parent" 2018-06-12 20:52:16 -07:00
devpts
dlm treewide: Use array_size() in vmalloc() 2018-06-12 16:19:22 -07:00
ecryptfs Merge branch 'fixes' of https://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs into aio-base 2018-05-26 09:16:25 +02:00
efivarfs
efs
exofs exofs: avoid VLA in structures 2018-06-15 07:55:24 +09:00
exportfs ovl: do not try to reconnect a disconnected origin dentry 2018-04-12 12:04:49 +02:00
ext2 treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
ext4 vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
f2fs vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
fat Merge branch 'akpm' (patches from Andrew) 2018-06-15 08:51:42 +09:00
freevxfs freevxfs_lookup(): use d_splice_alias() 2018-05-22 14:27:51 -04:00
fscache proc: introduce proc_create_single{,_data} 2018-05-16 07:23:35 +02:00
fuse vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
gfs2 vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
hfs vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
hfsplus vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
hostfs vfs: change inode times to use struct timespec64 2018-06-05 16:57:31 -07:00
hpfs treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
hugetlbfs alloc_file(): switch to passing O_... flags instead of FMODE_... mode 2018-07-12 10:02:57 -04:00
isofs isofs: fix potential memory leak in mount option parsing 2018-04-16 09:47:41 +02:00
jbd2 treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
jffs2 vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
jfs treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
kernfs vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
lockd
minix minix_lookup: use d_splice_alias() 2018-05-22 14:27:52 -04:00
nfs vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
nfs_common
nfsd vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
nilfs2 do d_instantiate/unlock_new_inode combinations safely 2018-05-11 15:36:37 -04:00
nls
notify fsnotify: add fsnotify_add_inode_mark() wrappers 2018-05-18 14:58:22 +02:00
ntfs vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
ocfs2 vfs: dedupe: rationalize args 2018-07-06 23:57:03 +02:00
omfs omfs_lookup(): report IO errors, use d_splice_alias() 2018-05-22 14:27:58 -04:00
openpromfs openpromfs: switch to d_splice_alias() 2018-05-22 14:27:57 -04:00
orangefs Solve a series of broken links for files under Documentation: 2018-06-17 05:25:18 +09:00
overlayfs ovl: A new xattr OVL_XATTR_METACOPY for file on upper 2018-07-20 09:56:08 +02:00
proc proc: add proc_seq_release 2018-06-27 20:44:38 -04:00
pstore pstore: Remove bogus format string definition 2018-06-14 14:57:24 +02:00
qnx4 qnx4_lookup: use d_splice_alias() 2018-05-22 14:27:52 -04:00
qnx6 qnx6_lookup: switch to d_splice_alias() 2018-05-22 14:27:54 -04:00
quota fs: quota: Replace GFP_ATOMIC with GFP_KERNEL in dquot_init 2018-04-09 17:48:54 +02:00
ramfs
reiserfs vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
romfs romfs_lookup: switch to d_splice_alias() 2018-05-22 14:27:55 -04:00
squashfs
sysfs unfuck sysfs_mount() 2018-05-21 14:30:09 -04:00
sysv sysv_lookup: use d_splice_alias() 2018-05-22 14:27:53 -04:00
tracefs
ubifs vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
udf vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
ufs treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
xfs vfs: dedupe: rationalize args 2018-07-06 23:57:03 +02:00
aio.c alloc_file(): switch to passing O_... flags instead of FMODE_... mode 2018-07-12 10:02:57 -04:00
anon_inodes.c alloc_file(): switch to passing O_... flags instead of FMODE_... mode 2018-07-12 10:02:57 -04:00
attr.c vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
bad_inode.c vfs: change inode times to use struct timespec64 2018-06-05 16:57:31 -07:00
binfmt_aout.c exec: introduce finalize_exec() before start_thread() 2018-04-11 10:28:37 -07:00
binfmt_elf_fdpic.c treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
binfmt_elf.c coredump: fix spam with zero VMA process 2018-06-15 07:55:24 +09:00
binfmt_em86.c
binfmt_flat.c exec: introduce finalize_exec() before start_thread() 2018-04-11 10:28:37 -07:00
binfmt_misc.c turn filp_clone_open() into inline wrapper for dentry_open() 2018-07-10 23:29:03 -04:00
binfmt_script.c
block_dev.c treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
buffer.c fs: move page_cache_seek_hole_data to iomap.c 2018-06-01 18:37:33 -07:00
char_dev.c
compat_binfmt_elf.c
compat_ioctl.c autofs: clean up includes 2018-06-07 17:34:40 -07:00
compat.c ncpfs: remove compat functionality 2018-06-05 19:23:26 +02:00
coredump.c
d_path.c
dax.c libnvdimm for 4.18 2018-06-08 17:21:52 -07:00
dcache.c Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-06-04 10:14:28 -07:00
dcookies.c
direct-io.c block: consistently use GFP_NOIO instead of __GFP_NORECLAIM 2018-05-14 08:55:18 -06:00
drop_caches.c
eventfd.c eventfd: only return events requested in poll_mask() 2018-06-14 20:07:38 -04:00
eventpoll.c eventpoll: switch to ->poll_mask 2018-06-14 20:09:28 -04:00
exec.c Merge branch 'core-rseq-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-06-10 10:17:09 -07:00
fcntl.c mm: restructure memfd code 2018-06-07 17:34:35 -07:00
fhandle.c
file_table.c vfs: make open_with_fake_path() not contribute to nr_files 2018-07-18 15:44:40 +02:00
file.c
filesystems.c proc: introduce proc_create_single{,_data} 2018-05-16 07:23:35 +02:00
fs_pin.c
fs_struct.c
fs-writeback.c bdi: Fix oops in wb_workfn() 2018-05-03 16:11:37 -06:00
inode.c Revert "vfs: update ovl inode before relatime check" 2018-07-18 15:44:43 +02:00
internal.h Revert "vfs: update ovl inode before relatime check" 2018-07-18 15:44:43 +02:00
ioctl.c vfs: export vfs_ioctl() to modules 2018-07-18 15:44:40 +02:00
iomap.c Changes since last update: 2018-06-12 15:49:00 -07:00
Kconfig autofs: remove left-over autofs4 stubs 2018-06-11 08:22:34 -07:00
Kconfig.binfmt docs: Fix more broken references 2018-06-15 18:11:26 -03:00
libfs.c
locks.c Partially revert "locks: fix file locking on overlayfs" 2018-07-18 15:44:43 +02:00
Makefile autofs: remove left-over autofs4 stubs 2018-06-11 08:22:34 -07:00
mbcache.c treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
mount.h
mpage.c
namei.c Revert "vfs: update ovl inode before relatime check" 2018-07-18 15:44:43 +02:00
namespace.c vfs: fix freeze protection in mnt_want_write_file() for overlayfs 2018-07-18 15:44:43 +02:00
no-block.c
nsfs.c
open.c Revert "vfs: do get_write_access() on upper layer of overlayfs" 2018-07-18 15:44:43 +02:00
pipe.c alloc_file(): switch to passing O_... flags instead of FMODE_... mode 2018-07-12 10:02:57 -04:00
pnode.c
pnode.h
posix_acl.c
proc_namespace.c
read_write.c vfs: export vfs_dedupe_file_range_one() to modules 2018-07-18 15:44:40 +02:00
readdir.c
select.c treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
seq_file.c proc: fix smaps and meminfo alignment 2018-05-25 18:12:11 -07:00
signalfd.c Merge branch 'work.compat' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-06-16 16:21:50 +09:00
splice.c Merge branch 'work.compat' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-06-16 16:21:50 +09:00
stack.c
stat.c
statfs.c
super.c Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-06-04 10:14:28 -07:00
sync.c Changes for this release: 2018-04-04 12:44:02 -07:00
timerfd.c timerfd: convert to ->poll_mask 2018-05-26 09:16:44 +02:00
userfaultfd.c userfaultfd: prevent non-cooperative events vs mcopy_atomic races 2018-06-07 17:34:38 -07:00
utimes.c
xattr.c Revert "ovl: don't allow writing ioctl on lower layer" 2018-07-18 15:44:43 +02:00