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Greg Kurz 2d82ab251e virtiofs: propagate sync() to file server 
Even if POSIX doesn't mandate it, linux users legitimately expect sync() to
flush all data and metadata to physical storage when it is located on the
same system.  This isn't happening with virtiofs though: sync() inside the
guest returns right away even though data still needs to be flushed from
the host page cache.

This is easily demonstrated by doing the following in the guest:

$ dd if=/dev/zero of=/mnt/foo bs=1M count=5K ; strace -T -e sync sync
5120+0 records in
5120+0 records out
5368709120 bytes (5.4 GB, 5.0 GiB) copied, 5.22224 s, 1.0 GB/s
sync()                                  = 0 <0.024068>

and start the following in the host when the 'dd' command completes
in the guest:

$ strace -T -e fsync /usr/bin/sync virtiofs/foo
fsync(3)                                = 0 <10.371640>

There are no good reasons not to honor the expected behavior of sync()
actually: it gives an unrealistic impression that virtiofs is super fast
and that data has safely landed on HW, which isn't the case obviously.

Implement a ->sync_fs() superblock operation that sends a new FUSE_SYNCFS
request type for this purpose.  Provision a 64-bit placeholder for possible
future extensions.  Since the file server cannot handle the wait == 0 case,
we skip it to avoid a gratuitous roundtrip.  Note that this is
per-superblock: a FUSE_SYNCFS is send for the root mount and for each
submount.

Like with FUSE_FSYNC and FUSE_FSYNCDIR, lack of support for FUSE_SYNCFS in
the file server is treated as permanent success.  This ensures
compatibility with older file servers: the client will get the current
behavior of sync() not being propagated to the file server.

Note that such an operation allows the file server to DoS sync().  Since a
typical FUSE file server is an untrusted piece of software running in
userspace, this is disabled by default.  Only enable it with virtiofs for
now since virtiofsd is supposedly trusted by the guest kernel.

Reported-by: Robert Krawitz <rlk@redhat.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2021-06-22 09:15:35 +02:00
..
9p 9p for 5.13-rc1 2021-05-07 11:18:52 -07:00
adfs fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
affs idmapped-mounts-v5.12 2021-02-23 13:39:45 -08:00
afs afs: Fix the nlink handling of dir-over-dir rename 2021-05-27 06:23:58 -10:00
autofs autofs: should_expire() argument is guaranteed to be positive 2021-03-24 14:14:27 -04:00
befs fs/befs: Delete obsolete TODO file 2021-03-30 16:54:49 -07:00
bfs fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
btrfs for-5.13-rc4-tag 2021-06-03 11:37:14 -07:00
cachefiles fscache, cachefiles: Add alternate API to use kiocb for read/write to cache 2021-04-23 10:14:32 +01:00
ceph Notable items here are a series to take advantage of David Howells' 2021-05-06 10:27:02 -07:00
cifs cifs: change format of CIFS_FULL_KEY_DUMP ioctl 2021-05-27 15:26:32 -05:00
coda coda: fix reference counting in coda_file_mmap error path 2021-04-23 14:42:39 -07:00
configfs treewide: remove editor modelines and cruft 2021-05-07 00:26:34 -07:00
cramfs cramfs: use %pD instead of messing with file_dentry()->d_name 2021-01-05 23:02:47 -05:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2021-04-26 08:51:23 -07:00
debugfs debugfs: fix security_locked_down() call for SELinux 2021-05-18 18:05:59 +02:00
devpts
dlm fs: dlm: fix missing unlock on error in accept_from_sock() 2021-03-29 13:28:18 -05:00
ecryptfs fs: ecryptfs: remove BUG_ON from crypt_scatterlist 2021-05-13 18:32:26 +02:00
efivarfs efivars: convert to fileattr 2021-04-12 15:04:29 +02:00
efs [PATCH] reduce boilerplate in fsid handling 2020-09-18 16:45:50 -04:00
erofs erofs: fix 1 lcluster-sized pcluster for big pcluster 2021-05-13 15:58:46 +08:00
exfat exfat: speed up iterate/lookup by fixing start point of traversing cluster chain 2021-04-27 20:45:07 +09:00
exportfs exportfs: Add a function to return the raw output from fh_to_dentry() 2020-12-09 09:39:38 -05:00
ext2 Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2021-05-02 09:14:01 -07:00
ext4 Miscellaneous ext4 bug fixes for v5.13 2021-06-06 14:24:13 -07:00
f2fs f2fs: return EINVAL for hole cases in swap file 2021-05-12 07:38:00 -07:00
fat fs: fat: fix spelling typo of values 2021-05-07 00:26:34 -07:00
freevxfs
fscache fscache, cachefiles: Add alternate API to use kiocb for read/write to cache 2021-04-23 10:14:32 +01:00
fuse virtiofs: propagate sync() to file server 2021-06-22 09:15:35 +02:00
gfs2 Revert "gfs2: Fix mmap locking for write faults" 2021-06-01 23:16:42 +02:00
hfs fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
hfsplus hfsplus: prevent corruption in shrinking truncate 2021-05-14 19:41:32 -07:00
hostfs Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2021-05-02 09:14:01 -07:00
hpfs hpfs: replace one-element array with flexible-array member 2021-05-06 19:24:13 -07:00
hugetlbfs userfaultfd: hugetlbfs: fix new flag usage in error path 2021-05-22 15:09:07 -10:00
iomap mm/filemap: fix readahead return types 2021-05-14 19:41:32 -07:00
isofs isofs: fix fall-through warnings for Clang 2021-05-06 19:24:13 -07:00
jbd2 ext4: fix debug format string warning 2021-04-09 23:32:16 -04:00
jffs2 This pull request contains changes for JFFS2, UBI and UBIFS 2021-05-04 18:08:40 -07:00
jfs jfs: convert to fileattr 2021-04-12 15:04:29 +02:00
kernfs idmapped-mounts-v5.12 2021-02-23 13:39:45 -08:00
lockd SUNRPC: Make trace_svc_process() display the RPC procedure symbolically 2021-01-25 09:36:23 -05:00
minix fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
netfs netfs: Make CONFIG_NETFS_SUPPORT auto-selected rather than manual 2021-05-25 13:48:04 +01:00
nfs nfs: Remove trailing semicolon in macros 2021-05-27 09:19:33 -04:00
nfs_common NFSD: Add an xdr_stream-based encoder for NFSv2/3 ACLs 2021-03-22 10:19:00 -04:00
nfsd NFS client updates for Linux 5.13 2021-05-07 11:23:41 -07:00
nilfs2 Merge branch 'akpm' (patches from Andrew) 2021-05-07 00:34:51 -07:00
nls
notify fanotify: fix permission model of unprivileged group 2021-05-25 12:21:14 +02:00
ntfs ntfs: check for valid standard information attribute 2021-02-24 13:38:26 -08:00
ocfs2 ocfs2: fix data corruption by fallocate 2021-06-05 08:58:12 -07:00
omfs fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
openpromfs openpromfs: don't do unlock_new_inode() until the new inode is set up 2021-03-12 22:15:22 -05:00
orangefs orangefs: leave files in the page cache for a few micro seconds at least 2021-04-29 08:06:05 -04:00
overlayfs overlayfs update for 5.13 2021-04-30 15:17:08 -07:00
proc proc: Check /proc/$pid/attr/ writes against file opener 2021-05-25 10:24:41 -10:00
pstore printk changes for 5.13 2021-04-27 18:09:44 -07:00
qnx4 [PATCH] reduce boilerplate in fsid handling 2020-09-18 16:45:50 -04:00
qnx6 [PATCH] reduce boilerplate in fsid handling 2020-09-18 16:45:50 -04:00
quota quota: Use 'hlist_for_each_entry' to simplify code 2021-05-10 16:27:49 +02:00
ramfs ramfs: support O_TMPFILE 2021-02-24 13:38:26 -08:00
reiserfs treewide: remove editor modelines and cruft 2021-05-07 00:26:34 -07:00
romfs Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-10-24 12:26:05 -07:00
squashfs squashfs: fix divide error in calculate_skip() 2021-05-14 19:41:32 -07:00
sysfs sysfs: Support zapping of binary attr mmaps 2021-01-12 14:26:31 +01:00
sysv fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
tracefs tracing: Fix various typos in comments 2021-03-23 14:08:18 -04:00
ubifs This pull request contains changes for JFFS2, UBI and UBIFS 2021-05-04 18:08:40 -07:00
udf useful constants: struct qstr for ".." 2021-04-15 22:36:45 -04:00
ufs useful constants: struct qstr for ".." 2021-04-15 22:36:45 -04:00
unicode .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
vboxsf vboxsf: don't allow to change the inode type 2021-03-12 22:15:00 -05:00
verity fsverity: relax build time dependency on CRYPTO_SHA256 2021-04-22 17:31:32 +10:00
xfs xfs: bunmapi has unnecessary AG lock ordering issues 2021-05-27 08:11:24 -07:00
zonefs \n 2021-04-29 11:06:13 -07:00
aio.c Revert "mremap: don't allow MREMAP_DONTUNMAP on special_mappings and aio" 2021-04-30 11:20:39 -07:00
anon_inodes.c fs: anon_inodes: rephrase to appropriate kernel-doc 2021-01-15 12:17:25 -05:00
attr.c ima: handle idmapped mounts 2021-01-24 14:27:20 +01:00
bad_inode.c fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
binfmt_aout.c
binfmt_elf.c coredump: don't bother with do_truncate() 2021-03-08 10:21:11 -05:00
binfmt_elf_fdpic.c coredump: don't bother with do_truncate() 2021-03-08 10:21:11 -05:00
binfmt_em86.c
binfmt_flat.c binfmt_flat: allow not offsetting data start 2021-04-19 09:56:37 +10:00
binfmt_misc.c binfmt_misc: fix possible deadlock in bm_register_write 2021-03-13 11:27:30 -08:00
binfmt_script.c
block_dev.c block-5.13-2021-05-22 2021-05-22 07:40:34 -10:00
buffer.c Merge branch 'akpm' (patches from Andrew) 2021-05-05 13:50:15 -07:00
char_dev.c
compat_binfmt_elf.c get rid of COMPAT_ELF_EXEC_PAGESIZE 2021-01-06 08:42:51 -05:00
coredump.c coredump: don't bother with do_truncate() 2021-03-08 10:21:11 -05:00
d_path.c constify dentry argument of dentry_path()/dentry_path_raw() 2021-03-21 11:43:58 -04:00
dax.c dax fixes for 5.13-rc2 2021-05-15 08:28:08 -07:00
dcache.c useful constants: struct qstr for ".." 2021-04-15 22:36:45 -04:00
direct-io.c fs: direct-io: fix missing sdio->boundary 2021-04-09 14:54:23 -07:00
drop_caches.c
eventfd.c eventfd: Export eventfd_ctx_do_read() 2020-11-15 09:49:10 -05:00
eventpoll.c fs/epoll: restore waking from ep_done_scan() 2021-05-06 19:24:13 -07:00
exec.c fs: delete repeated words in comments 2021-02-24 13:38:26 -08:00
fcntl.c idmapped-mounts-v5.12 2021-02-23 13:39:45 -08:00
fhandle.c fs: delete repeated words in comments 2021-02-24 13:38:26 -08:00
file.c Merge branch 'work.file' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2021-05-03 11:05:28 -07:00
file_table.c epoll: take epitem list out of struct file 2020-10-25 20:02:08 -04:00
filesystems.c
fs-writeback.c fs: improve comments for writeback_single_inode() 2021-01-13 17:26:50 +01:00
fs_context.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
fs_parser.c vfs: fs_parser: clean up kernel-doc warnings 2021-04-30 11:20:35 -07:00
fs_pin.c
fs_struct.c
fs_types.c
fsopen.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
init.c init: handle idmapped mounts 2021-01-24 14:27:19 +01:00
inode.c mm: remove nrexceptional from inode: remove BUG_ON 2021-05-05 11:27:20 -07:00
internal.h idmapped-mounts-v5.12 2021-02-23 13:39:45 -08:00
io-wq.c io-wq: Fix UAF when wakeup wqe in hash waitqueue 2021-05-26 09:03:56 -06:00
io-wq.h io_uring/io-wq: close io-wq full-stop gap 2021-05-25 19:39:58 -06:00
io_uring.c io_uring: fix misaccounting fix buf pinned pages 2021-05-29 19:27:21 -06:00
ioctl.c vfs: add fileattr ops 2021-04-12 15:04:23 +02:00
Kconfig NFS client updates for Linux 5.13 2021-05-07 11:23:41 -07:00
Kconfig.binfmt binfmt_flat: allow not offsetting data start 2021-04-19 09:56:37 +10:00
kernel_read_file.c fs/kernel_file_read: Add "offset" arg for partial reads 2020-10-05 13:37:04 +02:00
libfs.c libfs: fix kernel-doc for mnt_userns 2021-03-23 11:20:25 +01:00
locks.c Additional fixes and clean-ups for NFSD since tags/nfsd-5.13, 2021-05-05 13:44:19 -07:00
Makefile netfs: Provide readahead and readpage netfs helpers 2021-04-23 10:14:32 +01:00
mbcache.c
mount.h mount: make {lock,unlock}_mount_hash() static 2021-01-24 14:29:34 +01:00
mpage.c block: rename BIO_MAX_PAGES to BIO_MAX_VECS 2021-03-11 07:47:48 -07:00
namei.c fs.idmapped.helpers.v5.13 2021-04-27 12:49:42 -07:00
namespace.c fs/mount_setattr: tighten permission checks 2021-05-12 14:13:16 +02:00
no-block.c
nsfs.c
open.c idmapped-mounts-v5.12 2021-02-23 13:39:45 -08:00
pipe.c fs: delete repeated words in comments 2021-02-24 13:38:26 -08:00
pnode.c
pnode.h mount: fix mounting of detached mounts onto targets that reside on shared mounts 2021-03-08 15:18:43 +01:00
posix_acl.c fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
proc_namespace.c fs: introduce MOUNT_ATTR_IDMAP 2021-01-24 14:43:45 +01:00
read_write.c teach sendfile(2) to handle send-to-pipe directly 2021-01-25 23:29:36 -05:00
readdir.c readdir: make sure to verify directory entry for legacy interfaces too 2021-04-17 11:39:49 -07:00
remap_range.c ioctl: handle idmapped mounts 2021-01-24 14:27:19 +01:00
select.c kernel, fs: Introduce and use set_restart_fn() and arch_set_restart_data() 2021-03-16 22:13:10 +01:00
seq_file.c seq_file: Add a seq_bprintf function 2021-04-27 15:50:15 -07:00
signalfd.c signalfd: Remove SIL_PERF_EVENT fields from signalfd_siginfo 2021-05-18 16:20:54 -05:00
splice.c for-5.12/block-2021-02-17 2021-02-21 11:02:48 -08:00
stack.c
stat.c fs: fix reporting supported extra file attributes for statx() 2021-04-17 23:03:50 -04:00
statfs.c s390,alpha: switch to 64-bit ino_t 2021-02-13 17:17:53 +01:00
super.c fs,security: Add sb_delete hook 2021-04-22 12:22:11 -07:00
sync.c
timerfd.c
userfaultfd.c userfaultfd: add UFFDIO_CONTINUE ioctl 2021-05-05 11:27:22 -07:00
utimes.c utimes: handle idmapped mounts 2021-01-24 14:27:18 +01:00
xattr.c xattr: fix kernel-doc for mnt_userns and vfs xattr helpers 2021-03-23 11:20:26 +01:00