net/9p: use a dedicated spinlock for trans_fd

Shamelessly copying the explanation from Tetsuo Handa's suggested
patch[1] (slightly reworded):
syzbot is reporting inconsistent lock state in p9_req_put()[2],
for p9_tag_remove() from p9_req_put() from IRQ context is using
spin_lock_irqsave() on "struct p9_client"->lock but trans_fd
(not from IRQ context) is using spin_lock().

Since the locks actually protect different things in client.c and in
trans_fd.c, just replace trans_fd.c's lock by a new one specific to the
transport (client.c's protect the idr for fid/tag allocations,
while trans_fd.c's protects its own req list and request status field
that acts as the transport's state machine)

Link: https://lore.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected] [1]
Link: https://syzkaller.appspot.com/bug?extid=2f20b523930c32c160cc [2]
Reported-by: syzbot <[email protected]>
Reported-by: Tetsuo Handa <[email protected]>
Reviewed-by: Christian Schoenebeck <[email protected]>
Signed-off-by: Dominique Martinet <[email protected]>

0 files changed, 0 insertions, 0 deletions