Multi write opens will go into __fscache_disable_cookie and cookie->n_active may be zero for a short window. Move this assertion under locking to avoid assert failure for ASSERTCMP(atomic_read(&cookie->n_active), >, 0).

stack is as following:

fscache_disable_cookie include/linux/fscache.h:854 [inline] nfs_fscache_open_file+0x3ba/0x430 fs/nfs/fscache.c:319 nfs4_file_open+0x4ff/0x780 fs/nfs/nfs4file.c:90 do_dentry_open+0x6ea/0x1170 fs/open.c:826 do_open.isra.0+0x9dc/0xf50 fs/namei.c:3316 path_openat+0x336/0x810 fs/namei.c:3434 do_filp_open+0x1b9/0x290 fs/namei.c:3461 do_sys_openat2+0x5be/0x9b0 fs/open.c:1231 do_sys_open+0xc8/0x150 fs/open.c:1248 do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x67/0xd1

Signed-off-by: zhangjian zhangjian496@huawei.com --- fs/fscache/cookie.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c index 6104f627c..30f0e2b41 100644 --- a/fs/fscache/cookie.c +++ b/fs/fscache/cookie.c @@ -703,6 +703,9 @@ void __fscache_disable_cookie(struct fscache_cookie *cookie,

_enter("%p,%u", cookie, invalidate);

+ wait_on_bit_lock(&cookie->flags, FSCACHE_COOKIE_ENABLEMENT_LOCK, + TASK_UNINTERRUPTIBLE); + trace_fscache_disable(cookie);

ASSERTCMP(atomic_read(&cookie->n_active), >, 0); @@ -713,9 +716,6 @@ void __fscache_disable_cookie(struct fscache_cookie *cookie, BUG(); }

- wait_on_bit_lock(&cookie->flags, FSCACHE_COOKIE_ENABLEMENT_LOCK, - TASK_UNINTERRUPTIBLE); - fscache_update_aux(cookie, aux_data);

if (!test_and_clear_bit(FSCACHE_COOKIE_ENABLED, &cookie->flags))