Hi Song,
Paulo Alcantara <pc@xxxxxxxxxxxxx> writes:
> Song Liu <song@xxxxxxxxxx> writes:
>
>> When testing a special config:
>>
>> CONFIG_NETFS_SUPPORTS=y
>> CONFIG_PROC_FS=n
>>
>> The system crashes with something like:
>>
>> [ 3.766197] ------------[ cut here ]------------
>> [ 3.766484] kernel BUG at mm/mempool.c:560!
>> [ 3.766789] Oops: invalid opcode: 0000 [#1] SMP NOPTI
>> [ 3.767123] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Tainted: G W
>> [ 3.767777] Tainted: [W]=WARN
>> [ 3.767968] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
>> [ 3.768523] RIP: 0010:mempool_alloc_slab.cold+0x17/0x19
>> [ 3.768847] Code: 50 fe ff 58 5b 5d 41 5c 41 5d 41 5e 41 5f e9 93 95 13 00
>> [ 3.769977] RSP: 0018:ffffc90000013998 EFLAGS: 00010286
>> [ 3.770315] RAX: 000000000000002f RBX: ffff888100ba8640 RCX: 0000000000000000
>> [ 3.770749] RDX: 0000000000000000 RSI: 0000000000000003 RDI: 00000000ffffffff
>> [ 3.771217] RBP: 0000000000092880 R08: 0000000000000000 R09: ffffc90000013828
>> [ 3.771664] R10: 0000000000000001 R11: 00000000ffffffea R12: 0000000000092cc0
>> [ 3.772117] R13: 0000000000000400 R14: ffff8881004b1620 R15: ffffea0004ef7e40
>> [ 3.772554] FS: 0000000000000000(0000) GS:ffff8881b5f3c000(0000) knlGS:0000000000000000
>> [ 3.773061] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [ 3.773443] CR2: ffffffff830901b4 CR3: 0000000004296001 CR4: 0000000000770ef0
>> [ 3.773884] PKRU: 55555554
>> [ 3.774058] Call Trace:
>> [ 3.774232] <TASK>
>> [ 3.774371] mempool_alloc_noprof+0x6a/0x190
>> [ 3.774649] ? _printk+0x57/0x80
>> [ 3.774862] netfs_alloc_request+0x85/0x2ce
>> [ 3.775147] netfs_readahead+0x28/0x170
>> [ 3.775395] read_pages+0x6c/0x350
>> [ 3.775623] ? srso_alias_return_thunk+0x5/0xfbef5
>> [ 3.775928] page_cache_ra_unbounded+0x1bd/0x2a0
>> [ 3.776247] filemap_get_pages+0x139/0x970
>> [ 3.776510] ? srso_alias_return_thunk+0x5/0xfbef5
>> [ 3.776820] filemap_read+0xf9/0x580
>> [ 3.777054] ? srso_alias_return_thunk+0x5/0xfbef5
>> [ 3.777368] ? srso_alias_return_thunk+0x5/0xfbef5
>> [ 3.777674] ? find_held_lock+0x32/0x90
>> [ 3.777929] ? netfs_start_io_read+0x19/0x70
>> [ 3.778221] ? netfs_start_io_read+0x19/0x70
>> [ 3.778489] ? srso_alias_return_thunk+0x5/0xfbef5
>> [ 3.778800] ? lock_acquired+0x1e6/0x450
>> [ 3.779054] ? srso_alias_return_thunk+0x5/0xfbef5
>> [ 3.779379] netfs_buffered_read_iter+0x57/0x80
>> [ 3.779670] __kernel_read+0x158/0x2c0
>> [ 3.779927] bprm_execve+0x300/0x7a0
>> [ 3.780185] kernel_execve+0x10c/0x140
>> [ 3.780423] ? __pfx_kernel_init+0x10/0x10
>> [ 3.780690] kernel_init+0xd5/0x150
>> [ 3.780910] ret_from_fork+0x2d/0x50
>> [ 3.781156] ? __pfx_kernel_init+0x10/0x10
>> [ 3.781414] ret_from_fork_asm+0x1a/0x30
>> [ 3.781677] </TASK>
>> [ 3.781823] Modules linked in:
>> [ 3.782065] ---[ end trace 0000000000000000 ]---
>>
>> This is caused by the following error path in netfs_init():
>>
>> if (!proc_mkdir("fs/netfs", NULL))
>> goto error_proc;
>>
>> Fix this by letting netfs depends on PROC_FS.
>>
>> Signed-off-by: Song Liu <song@xxxxxxxxxx>
>> ---
>> fs/netfs/Kconfig | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> Reviewed-by: Paulo Alcantara (Red Hat) <pc@xxxxxxxxxxxxx>
Sorry, I take it back. Reviewed it way too soon :-/
It wouldn't make sense to make it depend on PROC_FS.
I see two problems here:
(1) We shouldn't be creating /proc/fs/netfs if CONFIG_PROC_FS=n
(2) There's a wrong assumption in the API that @netfs_request_pool and
@netfs_subrequest_pool will always be initialized. For example, we
should return an error from netfs_alloc_[sub]rquest() functions in case
@mempool == NULL.
Dave, any thoughts?
