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Miklos Szeredi 8039a47e67 fix shrink_dcache_parent() livelock 
commit eaf5f90735 upstream.

Two (or more) concurrent calls of shrink_dcache_parent() on the same dentry may
cause shrink_dcache_parent() to loop forever.

Here's what appears to happen:

1 - CPU0: select_parent(P) finds C and puts it on dispose list, returns 1

2 - CPU1: select_parent(P) locks P->d_lock

3 - CPU0: shrink_dentry_list() locks C->d_lock
   dentry_kill(C) tries to lock P->d_lock but fails, unlocks C->d_lock

4 - CPU1: select_parent(P) locks C->d_lock,
         moves C from dispose list being processed on CPU0 to the new
dispose list, returns 1

5 - CPU0: shrink_dentry_list() finds dispose list empty, returns

6 - Goto 2 with CPU0 and CPU1 switched

Basically select_parent() steals the dentry from shrink_dentry_list() and thinks
it found a new one, causing shrink_dentry_list() to think it's making progress
and loop over and over.

One way to trigger this is to make udev calls stat() on the sysfs file while it
is going away.

Having a file in /lib/udev/rules.d/ with only this one rule seems to the trick:

ATTR{vendor}=="0x8086", ATTR{device}=="0x10ca", ENV{PCI_SLOT_NAME}="%k", ENV{MATCHADDR}="$attr{address}", RUN+="/bin/true"

Then execute the following loop:

while true; do
        echo -bond0 > /sys/class/net/bonding_masters
        echo +bond0 > /sys/class/net/bonding_masters
        echo -bond1 > /sys/class/net/bonding_masters
        echo +bond1 > /sys/class/net/bonding_masters
done

One fix would be to check all callers and prevent concurrent calls to
shrink_dcache_parent().  But I think a better solution is to stop the
stealing behavior.

This patch adds a new dentry flag that is set when the dentry is added to the
dispose list.  The flag is cleared in dentry_lru_del() in case the dentry gets a
new reference just before being pruned.

If the dentry has this flag, select_parent() will skip it and let
shrink_dentry_list() retry pruning it.  With select_parent() skipping those
dentries there will not be the appearance of progress (new dentries found) when
there is none, hence shrink_dcache_parent() will not loop forever.

Set the flag is also set in prune_dcache_sb() for consistency as suggested by
Linus.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2012-01-25 17:24:51 -08:00
..
9p fs/9p: Use protocol-defined value for lock/getlock 'type' field. 2011-10-03 11:40:22 -07:00
adfs Fix common misspellings 2011-03-31 11:26:23 -03:00
affs affs: remove unnecessary dentry_unhash on rmdir, dir rename 2011-05-28 01:02:53 -04:00
afs AFS: Use i_generation not i_version for the vnode uniquifier 2011-06-16 11:44:48 -04:00
autofs4 autofs4: bogus dentry_unhash() added in ->unlink() 2011-05-30 01:50:53 -04:00
befs befs: Validate length of long symbolic links. 2011-08-29 13:29:06 -07:00
bfs bfs: remove unnecessary dentry_unhash on dir rename 2011-05-28 01:02:50 -04:00
btrfs btrfs: fix d_off in the first dirent 2011-10-03 11:41:03 -07:00
cachefiles Fix common misspellings 2011-03-31 11:26:23 -03:00
ceph ceph analog of cifs build_path_from_dentry() race fix 2011-07-16 23:43:58 -04:00
cifs CIFS: Fix DFS handling in cifs_get_file_info 2011-11-11 09:35:11 -08:00
coda coda_ioctl_permission() is safe in RCU mode 2011-06-20 10:44:19 -04:00
configfs configfs: remove unnecessary dentry_unhash on rmdir, dir rename 2011-05-28 01:02:54 -04:00
cramfs cramfs: get_cramfs_inode() returns ERR_PTR() on failure 2011-07-17 23:22:02 -04:00
debugfs debugfs: move to new strtobool 2011-05-19 16:55:28 +09:30
devpts fs/devpts/inode.c: correctly check d_alloc_name() return code in devpts_pty_new() 2011-03-22 17:44:17 -07:00
dlm Merge branch 'trivial' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6 2011-05-26 13:19:00 -07:00
ecryptfs eCryptfs: Extend array bounds for all filename chars 2011-12-09 08:52:19 -08:00
efs
exofs fix exofs ->get_parent() 2011-07-17 23:20:29 -04:00
exportfs
ext2 ext2: remove unnecessary dentry_unhash on rmdir/rename_dir 2011-05-26 07:26:56 -04:00
ext3 ext3: Don't warn from writepage when readonly inode is spotted after error 2012-01-12 11:35:06 -08:00
ext4 ext4: fix undefined behavior in ext4_fill_flex_info() 2012-01-25 17:24:33 -08:00
fat fat: Fix corrupt inode flags when remove ATTR_SYS flag 2011-05-31 19:42:24 +09:00
freevxfs treewide: fix a few typos in comments 2011-05-10 10:16:21 +02:00
fscache FS-Cache: Fix __fscache_uncache_all_inode_pages()'s outer loop 2011-07-21 10:59:16 -07:00
fuse fuse: fix fuse_retrieve 2011-12-21 12:57:44 -08:00
gfs2 GFS2: Fix mount hang caused by certain access pattern to sysfs files 2011-08-04 21:58:42 -07:00
hfs hfs: fix hfs_find_init() sb->ext_tree NULL ptr oops 2011-12-21 12:57:41 -08:00
hfsplus hfsplus: Fix kfree of wrong pointers in hfsplus_fill_super() error path 2011-10-25 07:10:17 +02:00
hostfs hostfs: remove unnecessary dentry_unhash on rmdir, dir rename 2011-05-28 01:02:52 -04:00
hpfs hpfs: remove unnecessary dentry_unhash on rmdir, dir rename 2011-05-28 01:02:54 -04:00
hppfs hppfs: missing include 2011-11-11 09:35:59 -08:00
hugetlbfs mm: don't access vm_flags as 'int' 2011-05-26 09:20:31 -07:00
isofs isofs: fix bh leak in isofs_fill_super() error case 2011-06-18 07:25:42 -07:00
jbd jbd/jbd2: validate sb->s_first in journal_get_superblock() 2011-12-21 12:57:40 -08:00
jbd2 jbd/jbd2: validate sb->s_first in journal_get_superblock() 2011-12-21 12:57:40 -08:00
jffs2 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2011-05-28 13:03:41 -07:00
jfs jfs: agstart field must be 64 bits 2011-06-20 17:53:24 -05:00
lockd NLM: Don't hang forever on NLM unlock requests 2011-06-15 11:24:27 -04:00
logfs logfs doesn't need ->permission() at all 2011-06-20 10:44:26 -04:00
minix minix: remove unnecessary dentry_unhash on rmdir, dir rename 2011-05-28 01:02:54 -04:00
ncpfs ncpfs: fix rename over directory with dangling references 2011-05-28 01:02:53 -04:00
nfs nfs: fix regression in handling of context= option in NFSv4 2012-01-25 17:24:36 -08:00
nfs_common Fix common misspellings 2011-03-31 11:26:23 -03:00
nfsd nfsd: Fix oops when parsing a 0 length export 2012-01-25 17:24:49 -08:00
nilfs2 nilfs2: unbreak compat ioctl 2012-01-06 14:13:52 -08:00
nls
notify fsnotify: don't BUG in fsnotify_destroy_mark() 2012-01-25 17:24:49 -08:00
ntfs Fix common misspellings 2011-03-31 11:26:23 -03:00
ocfs2 more conservative S_NOSEC handling 2011-06-03 18:24:58 -04:00
omfs Remove unneeded version.h includes from fs/ 2011-06-24 08:34:22 -07:00
openpromfs
partitions Revert "block: Remove extra discard_alignment from hd_struct." 2011-05-30 07:42:51 +02:00
proc fs/proc/meminfo.c: fix compilation error 2011-12-21 12:57:35 -08:00
pstore pstore: fix pstore filesystem mount/remount issue 2011-05-16 11:05:00 -07:00
qnx4
quota VFS: Fix the remaining automounter semantics regressions 2011-11-11 09:36:22 -08:00
ramfs ramfs: fix memleak on no-mmu arch 2011-04-14 16:06:56 -07:00
reiserfs reiserfs: Force inode evictions before umount to avoid crash 2012-01-12 11:35:05 -08:00
romfs romfs: fix romfs_get_unmapped_area() argument check 2011-06-27 18:00:12 -07:00
squashfs Merge git://git.kernel.org/pub/scm/linux/kernel/git/pkl/squashfs-linus 2011-05-29 11:19:45 -07:00
sysfs Delay struct net freeing while there's a sysfs instance refering to it 2011-06-12 17:45:41 -04:00
sysv sysv: remove unnecessary dentry_unhash from rmdir, dir rename 2011-05-28 01:02:50 -04:00
ubifs UBIFS: fix debugging messages 2012-01-25 17:24:45 -08:00
udf udf: Fix deadlock when converting file from in-ICB one to normal one 2012-01-12 11:35:09 -08:00
ufs ufs should use d_splice_alias() 2011-07-17 23:21:35 -04:00
xfs xfs: fix acl count validation in xfs_acl_from_disk() 2012-01-12 11:35:55 -08:00
aio.c Merge branch 'for-2.6.39/core' of git://git.kernel.dk/linux-2.6-block 2011-03-24 10:16:26 -07:00
anon_inodes.c
attr.c Cache xattr security drop check for write v2 2011-05-28 12:02:09 -04:00
bad_inode.c bad_inode_permission() is safe from RCU mode 2011-06-20 10:44:00 -04:00
binfmt_aout.c
binfmt_elf.c binfmt_elf: fix PIE execution with randomization disabled 2011-11-11 09:36:29 -08:00
binfmt_elf_fdpic.c FDPIC: Fix memory leak 2011-07-06 12:15:16 -07:00
binfmt_em86.c
binfmt_flat.c CRED: Fix load_flat_shared_library() to initialise bprm correctly 2011-05-03 10:10:51 +10:00
binfmt_misc.c
binfmt_script.c
binfmt_som.c
bio-integrity.c block: Require subsystems to explicitly allocate bio_set integrity mempool 2011-03-17 11:11:05 +01:00
bio.c block: improve the bio_add_page() and bio_add_pc_page() descriptions 2011-05-28 14:44:46 +02:00
block_dev.c block: make gendisk hold a reference to its queue 2011-11-11 09:37:07 -08:00
buffer.c vfs: Fix data corruption after failed write in __block_write_begin() 2011-06-16 11:44:46 -04:00
char_dev.c
compat.c exec: unify do_execve/compat_do_execve code 2011-04-09 15:53:56 +02:00
compat_binfmt_elf.c
compat_ioctl.c
dcache.c fix shrink_dcache_parent() livelock 2012-01-25 17:24:51 -08:00
dcookies.c oprofile, dcookies: Fix possible circular locking dependency 2011-05-31 16:33:35 +02:00
direct-io.c Merge branch 'for-2.6.39/core' of git://git.kernel.dk/linux-2.6-block 2011-03-24 10:16:26 -07:00
drop_caches.c vmscan: change shrinker API by passing shrink_control struct 2011-05-25 08:39:26 -07:00
eventfd.c
eventpoll.c epoll: fix spurious lockdep warnings 2011-11-11 09:35:29 -08:00
exec.c exec: do not call request_module() twice from search_binary_handler() 2011-10-16 14:14:54 -07:00
fcntl.c userns: rename is_owner_or_cap to inode_owner_or_capable 2011-03-23 19:47:13 -07:00
fhandle.c fs/fhandle.c: add <linux/personality.h> for ia64 2011-04-14 16:06:56 -07:00
fifo.c Filesystem: fifo: Fixed coding style issue. 2011-03-21 00:16:09 -04:00
file.c vfs: avoid large kmalloc()s for the fdtable 2011-04-28 11:28:20 -07:00
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: synchronize_rcu when unregister_filesystem success not failure 2011-04-17 10:42:01 -07:00
fs-writeback.c writeback: update dirtied_when for synced inode to prevent livelock 2011-10-03 11:40:44 -07:00
fs_struct.c
generic_acl.c userns: rename is_owner_or_cap to inode_owner_or_capable 2011-03-23 19:47:13 -07:00
inode.c mm: fix assertion mapping->nrpages == 0 in end_writeback() 2011-06-27 18:00:13 -07:00
internal.h fs: move i_wb_list out from under inode_lock 2011-03-24 21:17:51 -04:00
ioctl.c vfs: cleanup do_vfs_ioctl() 2011-03-21 00:16:08 -04:00
ioprio.c
Kconfig Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 2011-05-26 09:52:14 -07:00
Kconfig.binfmt
libfs.c fs/libfs.c: fix simple_attr_write() on 32bit machines 2011-07-19 22:09:30 -07:00
locks.c fs: fix lock initialization 2011-07-06 10:41:13 -07:00
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
mbcache.c vmscan: change shrinker API by passing shrink_control struct 2011-05-25 08:39:26 -07:00
mpage.c mm/fs: add hooks to support cleancache 2011-05-26 10:01:43 -06:00
namei.c VFS: we need to set LOOKUP_JUMPED on mountpoint crossing 2011-11-11 09:37:08 -08:00
namespace.c fix apparmor dereferencing potentially freed dentry, sanitize __d_path() API 2011-12-21 12:57:36 -08:00
nfsctl.c
no-block.c
open.c fs: Use BUG_ON(!mnt) at dentry_open(). 2011-03-21 01:10:41 -04:00
pipe.c
pnode.c
pnode.h
posix_acl.c
read_write.c
read_write.h
readdir.c
select.c select: remove unused MAX_SELECT_SECONDS 2011-03-21 00:16:08 -04:00
seq_file.c fix apparmor dereferencing potentially freed dentry, sanitize __d_path() API 2011-12-21 12:57:36 -08:00
signalfd.c
splice.c splice: add wakeup_pipe_readers() 2011-05-23 19:58:53 +02:00
stack.c
stat.c readlinkat: ensure we return ENOENT for the empty pathname for normal lookups 2011-11-11 09:36:19 -08:00
statfs.c VFS: fix statfs() automounter semantics regression 2011-11-11 09:37:08 -08:00
super.c more conservative S_NOSEC handling 2011-06-03 18:24:58 -04:00
sync.c Merge branch 'for-2.6.39/core' of git://git.kernel.dk/linux-2.6-block 2011-03-24 10:16:26 -07:00
timerfd.c timerfd: Fix wakeup of processes when timer is cancelled on clock change 2011-06-14 11:46:14 +02:00
utimes.c userns: rename is_owner_or_cap to inode_owner_or_capable 2011-03-23 19:47:13 -07:00
xattr.c Cache xattr security drop check for write v2 2011-05-28 12:02:09 -04:00
xattr_acl.c