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ac89b2ef9b
linux/fs
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Eryu Guan ac89b2ef9b 9p: don't maintain dir i_nlink if the exported fs doesn't either 
If the exported filesystem dir on 9p server doesn't maintain accurate
i_nlink count, e.g.  always reports i_nlink as 1, then 9p should not
maintain nlink count either, otherwise drop_link would report warning
with i_nlink being zero.

For example:

 - overlayfs sets nlink to 1 for merged dir

 - ext4 (with dir_nlink feature enabled) sets nlink to 1 if a dir has
   more than EXT4_LINK_MAX (65000) links.

In this case, everytime a stat(2) call (getattr) on such exported dirs
on 9p client side, the i_nlink gets reset to 1, then operations like
rmdir(2), unlink(2) and rename(2) would cause the dir nlink to go to
zero (then negative), which results in warnings in drop_nlink() and/or
inc_nlink() calls.

This can be reproduced easily as the following steps:

 - export a merged overlayfs dir via qemu virtfs to guest

 - mount the exported virtfs in guest

 - create two sub-directories in the root dir of the mounted 9pfs

 - stat the root dir of 9pfs, this resets nlink to 1

 - remove all subdirs, the second unlink/rmdir would trigger warning

  ------------[ cut here ]------------
  WARNING: CPU: 3 PID: 1284 at fs/inode.c:282 drop_nlink+0x3e/0x50
  ...
  Call Trace:
    dump_stack+0x63/0x81
    __warn+0xcb/0xf0
    warn_slowpath_null+0x1d/0x20
    drop_nlink+0x3e/0x50
    v9fs_remove+0xaa/0x130 [9p]
    v9fs_vfs_rmdir+0x13/0x20 [9p]
    vfs_rmdir+0xb7/0x130
    do_rmdir+0x1b8/0x230
    SyS_unlinkat+0x22/0x30
    do_syscall_64+0x67/0x180
  ---[ end trace 43758d8ba91e603b ]---

Fix it by leaving i_nlink to be 1 and don't drop nlink if a directory
has nlink <= 2, which indicates that the underlying exported fs doesn't
maintain nlink count accurately.  This follows what ext4 does in
ext4_dec_count().

Link: http://lkml.kernel.org/r/20180312053829.4367-1-eguan@linux.alibaba.com
Signed-off-by: Eryu Guan <eguan@linux.alibaba.com>
Reviewed-by: Yiwen Jiang <jiangyiwen@huawei.com>
Tested-by: Roman Kapl <code@rkapl.cz>
Cc: Caspar Zhang <caspar@linux.alibaba.com>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Ron Minnich <rminnich@sandia.gov>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Cc: <v9fs-developer@lists.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-04-05 21:36:22 -07:00
..
9p 9p: don't maintain dir i_nlink if the exported fs doesn't either 2018-04-05 21:36:22 -07:00
adfs Rename superblock flags (MS_xyz -> SB_xyz) 2017-11-27 13:05:09 -08:00
affs iversion: Rename make inode_cmp_iversion{+raw} to inode_eq_iversion{+raw} 2018-02-01 08:15:25 -05:00
afs Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-04-03 14:04:18 -07:00
autofs4 fs: add ksys_close() wrapper; remove in-kernel calls to sys_close() 2018-04-02 20:16:00 +02:00
befs befs: Define usercopy region in befs_inode_cache slab cache 2018-01-15 12:07:54 -08:00
bfs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
btrfs for-4.17-tag 2018-04-04 13:03:38 -07:00
cachefiles vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
ceph ceph: only dirty ITER_IOVEC pages for direct read 2018-03-30 11:17:48 +02:00
cifs cifs: Add minor debug message during negprot 2018-04-02 13:11:15 -05:00
coda vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
configfs configfs: make ci_type field, some pointers and function arguments const 2017-10-19 16:15:16 +02:00
cramfs cramfs: better MTD dependency expression 2018-02-08 11:37:31 -08:00
crypto fscrypt: fix build with pre-4.6 gcc versions 2018-02-01 10:51:18 -05:00
debugfs debugfs_lookup(): switch to lookup_one_len_unlocked() 2018-03-29 15:07:47 -04:00
devpts devpts: comment devpts_mntget() 2018-03-14 13:31:23 +01:00
dlm net: make getname() functions return length rather than use int* parameter 2018-02-12 14:15:04 -05:00
ecryptfs vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
efivarfs efivarfs: Limit the rate for non-root to read files 2018-02-22 10:21:02 -08:00
efs Rename superblock flags (MS_xyz -> SB_xyz) 2017-11-27 13:05:09 -08:00
exofs iversion.h related cleanup for v4.16 2018-02-07 14:25:22 -08:00
exportfs
ext2 iversion.h related cleanup for v4.16 2018-02-07 14:25:22 -08:00
ext4 ext4: force revalidation of directory pointer after seekdir(2) 2018-04-01 23:21:03 -04:00
f2fs Refactor support for encrypted symlinks to move common code to fscrypt. 2018-02-04 10:43:12 -08:00
fat iversion: Rename make inode_cmp_iversion{+raw} to inode_eq_iversion{+raw} 2018-02-01 08:15:25 -05:00
freevxfs vxfs: Define usercopy region in vxfs_inode slab cache 2018-01-15 12:07:57 -08:00
fscache sched/wait, fs/fscache: Convert wait_on_atomic_t() usage to the new wait_var_event() API 2018-03-20 08:23:21 +01:00
fuse vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
gfs2 gfs2: time journal recovery steps accurately 2018-03-29 10:41:27 -07:00
hfs Rename superblock flags (MS_xyz -> SB_xyz) 2017-11-27 13:05:09 -08:00
hfsplus hfsplus: honor setgid flag on directories 2018-02-06 18:32:45 -08:00
hostfs hostfs: rename do_rmdir() to hostfs_do_rmdir() 2018-04-02 20:15:53 +02:00
hpfs hpfs: don't bother with the i_version counter or f_version 2017-12-10 12:58:18 -08:00
hugetlbfs hugetlbfs: fix bug in pgoff overflow checking 2018-04-05 21:36:21 -07:00
isofs Rename superblock flags (MS_xyz -> SB_xyz) 2017-11-27 13:05:09 -08:00
jbd2 jbd2: if the journal is aborted then don't allow update of the log tail 2018-02-19 12:22:53 -05:00
jffs2 Documentation updates for 4.16. New stuff includes refcount_t 2018-01-31 19:25:25 -08:00
jfs Currently, hardened usercopy performs dynamic bounds checking on slab 2018-02-03 16:25:42 -08:00
kernfs vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
lockd net: Drop pernet_operations::async 2018-03-27 13:18:09 -04:00
minix treewide: simplify Kconfig dependencies for removed archs 2018-03-26 15:55:57 +02:00
nfs Merge branch 'sched-wait-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-04-02 16:50:39 -07:00
nfs_common net: Drop pernet_operations::async 2018-03-27 13:18:09 -04:00
nfsd net: Drop pernet_operations::async 2018-03-27 13:18:09 -04:00
nilfs2 nilfs2: use time64_t internally 2018-02-06 18:32:45 -08:00
nls License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
notify fanotify: add do_fanotify_mark() helper; remove in-kernel call to syscall 2018-04-02 20:15:45 +02:00
ntfs ntfs: remove i_version handling 2018-01-01 10:09:33 -05:00
ocfs2 ocfs2/dlm: clean up unused variable in dlm_process_recovery_data 2018-04-05 21:36:22 -07:00
omfs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
openpromfs Rename superblock flags (MS_xyz -> SB_xyz) 2017-11-27 13:05:09 -08:00
orangefs vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
overlayfs ovl: update Kconfig texts 2018-03-07 11:47:15 +01:00
proc net: Drop pernet_operations::async 2018-03-27 13:18:09 -04:00
pstore fs: pstore: remove unused hardirq.h 2017-11-28 16:39:09 -08:00
qnx4 Rename superblock flags (MS_xyz -> SB_xyz) 2017-11-27 13:05:09 -08:00
qnx6 Rename superblock flags (MS_xyz -> SB_xyz) 2017-11-27 13:05:09 -08:00
quota fs/quota: use COMPAT_SYSCALL_DEFINE for sys32_quotactl() 2018-04-02 20:15:47 +02:00
ramfs mm: make pagevec_lookup() update index 2017-09-06 17:27:26 -07:00
reiserfs fs/*/Kconfig: drop links to 404-compliant http://acl.bestbits.at 2018-01-01 12:45:37 -07:00
romfs Rename superblock flags (MS_xyz -> SB_xyz) 2017-11-27 13:05:09 -08:00
squashfs Rename superblock flags (MS_xyz -> SB_xyz) 2017-11-27 13:05:09 -08:00
sysfs sysfs: symlink: export sysfs_create_link_nowarn() 2018-03-19 21:14:26 -04:00
sysv Rename superblock flags (MS_xyz -> SB_xyz) 2017-11-27 13:05:09 -08:00
tracefs
ubifs Refactor support for encrypted symlinks to move common code to fscrypt. 2018-02-04 10:43:12 -08:00
udf udf: Sanitize nanoseconds for time stamps 2017-12-19 08:11:01 +01:00
ufs iversion.h related cleanup for v4.16 2018-02-07 14:25:22 -08:00
xfs xfs: do not log/recover swapext extent owner changes for deleted inodes 2018-03-29 10:19:15 -07:00
aio.c fs/aio: Use rcu_work instead of explicit rcu and work item 2018-03-19 10:12:03 -07:00
anon_inodes.c
attr.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
bad_inode.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
binfmt_aout.c fs: fix kernel_read prototype 2017-09-04 19:05:15 -04:00
binfmt_elf_fdpic.c Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-11-17 12:54:01 -08:00
binfmt_elf.c elf: fix NT_FILE integer overflow 2018-02-06 18:32:45 -08:00
binfmt_em86.c
binfmt_flat.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
binfmt_misc.c fs: add ksys_close() wrapper; remove in-kernel calls to sys_close() 2018-04-02 20:16:00 +02:00
binfmt_script.c exec: load_script: kill the onstack interp[BINPRM_BUF_SIZE] array 2017-10-03 17:54:25 -07:00
block_dev.c blockdev: Avoid two active bdev inodes for one device 2018-02-26 09:48:42 -07:00
buffer.c Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-01-31 09:25:20 -08:00
char_dev.c block, char_dev: Use correct format specifier for unsigned ints 2018-03-15 17:59:24 +01:00
compat_binfmt_elf.c
compat_ioctl.c fs: compat_ioctl: add new DVB demux ioctls 2017-12-28 11:17:29 -05:00
compat.c
coredump.c Merge branch 'misc.compat' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-11-17 11:54:55 -08:00
d_path.c split d_path() and friends into a separate file 2018-03-29 15:07:46 -04:00
dax.c Only miscellaneous cleanups and bug fixes for ext4 this cycle. 2018-02-03 13:49:22 -08:00
dcache.c d_genocide: move export to definition 2018-03-29 15:08:21 -04:00
dcookies.c fs: add do_lookup_dcookie() helper; remove in-kernel call to syscall 2018-04-02 20:15:39 +02:00
direct-io.c direct-io: Fix sleep in atomic due to sync AIO 2018-02-26 09:05:35 -07:00
drop_caches.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
eventfd.c fs: add do_eventfd() helper; remove internal call to sys_eventfd() 2018-04-02 20:15:39 +02:00
eventpoll.c fs: add do_epoll_*() helpers; remove internal calls to sys_epoll_*() 2018-04-02 20:15:37 +02:00
exec.c exec: Weaken dumpability for secureexec 2018-01-03 10:13:36 -08:00
fcntl.c fs: add do_compat_fcntl64() helper; remove in-kernel call to compat syscall 2018-04-02 20:15:42 +02:00
fhandle.c vfs: Copy struct mount.mnt_id to userspace using put_user() 2018-01-15 12:07:51 -08:00
file_table.c vfs: remove unused hardirq.h 2017-12-07 14:23:30 -05:00
file.c fs: add ksys_close() wrapper; remove in-kernel calls to sys_close() 2018-04-02 20:16:00 +02:00
filesystems.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fs_pin.c Merge branch 'linus' into locking/core, to resolve conflicts 2017-11-07 10:32:44 +01:00
fs_struct.c
fs-writeback.c writeback: update comment in inode_io_list_move_locked 2018-01-06 09:18:00 -07:00
inode.c inode: don't memset the inode address space twice 2018-03-11 20:27:56 -07:00
internal.h fs: add ksys_ftruncate() wrapper; remove in-kernel calls to sys_ftruncate() 2018-04-02 20:16:00 +02:00
ioctl.c fs: add ksys_ioctl() helper; remove in-kernel calls to sys_ioctl() 2018-04-02 20:16:03 +02:00
iomap.c iomap: warn on zero-length mappings 2018-01-29 07:27:24 -08:00
Kconfig libnvdimm for 4.16 2018-02-06 10:41:33 -08:00
Kconfig.binfmt treewide: simplify Kconfig dependencies for removed archs 2018-03-26 15:55:57 +02:00
libfs.c Rename superblock flags (MS_xyz -> SB_xyz) 2017-11-27 13:05:09 -08:00
locks.c This request is late, apologies. 2018-02-08 15:18:32 -08:00
Makefile split d_path() and friends into a separate file 2018-03-29 15:07:46 -04:00
mbcache.c mbcache: make sure c_entry_count is not decremented past zero 2018-01-09 23:57:52 -05:00
mount.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mpage.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
namei.c Merge branch 'work.dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-04-04 12:05:25 -07:00
namespace.c fs: add ksys_umount() helper; remove in-kernel call to sys_umount() 2018-04-02 20:15:48 +02:00
no-block.c
nsfs.c net: Export open_related_ns() 2018-02-15 15:34:42 -05:00
open.c fs: add ksys_fallocate() wrapper; remove in-kernel calls to sys_fallocate() 2018-04-02 20:16:09 +02:00
pipe.c fs: add do_pipe2() helper; remove internal call to sys_pipe2() 2018-04-02 20:15:35 +02:00
pnode.c
pnode.h
posix_acl.c posix_acl: convert posix_acl.a_refcount from atomic_t to refcount_t 2018-01-02 19:27:28 -08:00
proc_namespace.c vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
read_write.c fs: add ksys_p{read,write}64() helpers; remove in-kernel calls to syscalls 2018-04-02 20:16:09 +02:00
readdir.c fs: add ksys_getdents64() helper; remove in-kernel calls to sys_getdents64() 2018-04-02 20:16:02 +02:00
select.c fs: add do_compat_select() helper; remove in-kernel call to compat syscall 2018-04-02 20:15:42 +02:00
seq_file.c seq_file: fix incomplete reset on read from zero offset 2018-01-20 02:31:15 -05:00
signalfd.c fs: add do_compat_signalfd4() helper; remove in-kernel call to compat syscall 2018-04-02 20:15:43 +02:00
splice.c fs: add do_vmsplice() helper; remove in-kernel call to syscall 2018-04-02 20:15:40 +02:00
stack.c
stat.c fs: add do_readlinkat() helper; remove internal call to sys_readlinkat() 2018-04-02 20:15:34 +02:00
statfs.c Rename superblock flags (MS_xyz -> SB_xyz) 2017-11-27 13:05:09 -08:00
super.c Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-01-31 09:25:20 -08:00
sync.c Changes for this release: 2018-04-04 12:44:02 -07:00
timerfd.c vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
userfaultfd.c vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
utimes.c fs: add do_compat_futimesat() helper; remove in-kernel call to compat syscall 2018-04-02 20:15:44 +02:00
xattr.c lsm: fix smack_inode_removexattr and xattr_getsecurity memleak 2017-10-04 18:03:15 +11:00