[PATCH 0/2 v5] Fixups for l_pid

From: Benjamin Coddington
Date: Mon Jun 19 2017 - 09:24:33 EST

LTP fcntl tests (fcntl11 fcntl14 fcntl17 fcntl19 fcntl20 fcntl21) have been
failing for NFSv4 mounts due to an unexpected l_pid. What follows are some

v2: - Rebase onto linux-next
- Revert back to using the stack in locks_mandatory_area(), and fixup
patch description for 1/3

v3: - The lkp-robot found some serious per_thread_ops performance
regressions for v1 and v2, so this version changes things around to not
acquire a reference to struct pid in fl_nspid for every lock. Instead,
it drops fl_nspid altogether, and defers the lookup of the
namespace-translated pid until it actually needed.

v4: - Instead of looking up the virtual pid by way of referencing the struct
task of the that pid, instead use find_pid_ns() and pid_nr_ns(), which
avoids a the problem where we race to get a reference to the struct task
while it may be freed.

v5: - Squash previous 2/3 and 3/3 to avoid regression where F_GETLK would
return the init_ns pid instead of a translated pid.

Benjamin Coddington (2):
fs/locks: Use allocation rather than the stack in fcntl_getlk()
fs/locks: Remove fl_nspid and use fs-specific l_pid for remote locks

fs/locks.c | 116 ++++++++++++++++++++++++++++++++---------------------
include/linux/fs.h | 2 +-
2 files changed, 72 insertions(+), 46 deletions(-)