Commit c840b8e1 authored by Mike Snitzer's avatar Mike Snitzer Committed by Chuck Lever
Browse files

nfs_common: must not hold RCU while calling nfsd_file_put_local 



Move holding the RCU from nfs_to_nfsd_file_put_local to
nfs_to_nfsd_net_put.  It is the call to nfs_to->nfsd_serv_put that
requires the RCU anyway (the puts for nfsd_file and netns were
combined to avoid an extra indirect reference but that
micro-optimization isn't possible now).

This fixes xfstests generic/013 and it triggering:

"Voluntary context switch within RCU read-side critical section!"

[  143.545738] Call Trace:
[  143.546206]  <TASK>
[  143.546625]  ? show_regs+0x6d/0x80
[  143.547267]  ? __warn+0x91/0x140
[  143.547951]  ? rcu_note_context_switch+0x496/0x5d0
[  143.548856]  ? report_bug+0x193/0x1a0
[  143.549557]  ? handle_bug+0x63/0xa0
[  143.550214]  ? exc_invalid_op+0x1d/0x80
[  143.550938]  ? asm_exc_invalid_op+0x1f/0x30
[  143.551736]  ? rcu_note_context_switch+0x496/0x5d0
[  143.552634]  ? wakeup_preempt+0x62/0x70
[  143.553358]  __schedule+0xaa/0x1380
[  143.554025]  ? _raw_spin_unlock_irqrestore+0x12/0x40
[  143.554958]  ? try_to_wake_up+0x1fe/0x6b0
[  143.555715]  ? wake_up_process+0x19/0x20
[  143.556452]  schedule+0x2e/0x120
[  143.557066]  schedule_preempt_disabled+0x19/0x30
[  143.557933]  rwsem_down_read_slowpath+0x24d/0x4a0
[  143.558818]  ? xfs_efi_item_format+0x50/0xc0 [xfs]
[  143.559894]  down_read+0x4e/0xb0
[  143.560519]  xlog_cil_commit+0x1b2/0xbc0 [xfs]
[  143.561460]  ? _raw_spin_unlock+0x12/0x30
[  143.562212]  ? xfs_inode_item_precommit+0xc7/0x220 [xfs]
[  143.563309]  ? xfs_trans_run_precommits+0x69/0xd0 [xfs]
[  143.564394]  __xfs_trans_commit+0xb5/0x330 [xfs]
[  143.565367]  xfs_trans_roll+0x48/0xc0 [xfs]
[  143.566262]  xfs_defer_trans_roll+0x57/0x100 [xfs]
[  143.567278]  xfs_defer_finish_noroll+0x27a/0x490 [xfs]
[  143.568342]  xfs_defer_finish+0x1a/0x80 [xfs]
[  143.569267]  xfs_bunmapi_range+0x4d/0xb0 [xfs]
[  143.570208]  xfs_itruncate_extents_flags+0x13d/0x230 [xfs]
[  143.571353]  xfs_free_eofblocks+0x12e/0x190 [xfs]
[  143.572359]  xfs_file_release+0x12d/0x140 [xfs]
[  143.573324]  __fput+0xe8/0x2d0
[  143.573922]  __fput_sync+0x1d/0x30
[  143.574574]  nfsd_filp_close+0x33/0x60 [nfsd]
[  143.575430]  nfsd_file_free+0x96/0x150 [nfsd]
[  143.576274]  nfsd_file_put+0xf7/0x1a0 [nfsd]
[  143.577104]  nfsd_file_put_local+0x18/0x30 [nfsd]
[  143.578070]  nfs_close_local_fh+0x101/0x110 [nfs_localio]
[  143.579079]  __put_nfs_open_context+0xc9/0x180 [nfs]
[  143.580031]  nfs_file_clear_open_context+0x4a/0x60 [nfs]
[  143.581038]  nfs_file_release+0x3e/0x60 [nfs]
[  143.581879]  __fput+0xe8/0x2d0
[  143.582464]  __fput_sync+0x1d/0x30
[  143.583108]  __x64_sys_close+0x41/0x80
[  143.583823]  x64_sys_call+0x189a/0x20d0
[  143.584552]  do_syscall_64+0x64/0x170
[  143.585240]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[  143.586185] RIP: 0033:0x7f3c5153efd7

Fixes: 65f2a5c3 ("nfs_common: fix race in NFS calls to nfsd_file_put_local() and nfsd_serv_put()")
Signed-off-by: default avatarMike Snitzer <snitzer@kernel.org>
Reviewed-by: default avatarNeilBrown <neilb@suse.de>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent 07442ec8

fs/nfs_common/nfslocalio.c

+3 −5
Original line number Diff line number Diff line
@@ -155,11 +155,9 @@ struct nfsd_file *nfs_open_local_fh(nfs_uuid_t *uuid, 
	/* We have an implied reference to net thanks to nfsd_serv_try_get */

	localio = nfs_to->nfsd_open_local_fh(net, uuid->dom, rpc_clnt,

					     cred, nfs_fh, fmode);

	if (IS_ERR(localio)) {

		rcu_read_lock();

		nfs_to->nfsd_serv_put(net);

		rcu_read_unlock();

	}

	if (IS_ERR(localio))

		nfs_to_nfsd_net_put(net);



	return localio;

}

EXPORT_SYMBOL_GPL(nfs_open_local_fh);

fs/nfsd/filecache.c

+7 −7
Original line number Diff line number Diff line
@@ -391,19 +391,19 @@ nfsd_file_put(struct nfsd_file *nf) 
}



/**

 * nfsd_file_put_local - put the reference to nfsd_file and local nfsd_serv

 * @nf: nfsd_file of which to put the references

 * nfsd_file_put_local - put nfsd_file reference and arm nfsd_serv_put in caller

 * @nf: nfsd_file of which to put the reference

 *

 * First put the reference of the nfsd_file and then put the

 * reference to the associated nn->nfsd_serv.

 * First save the associated net to return to caller, then put

 * the reference of the nfsd_file.

 */

void

nfsd_file_put_local(struct nfsd_file *nf) __must_hold(rcu)

struct net *

nfsd_file_put_local(struct nfsd_file *nf)

{

	struct net *net = nf->nf_net;



	nfsd_file_put(nf);

	nfsd_serv_put(net);

	return net;

}



/**

fs/nfsd/filecache.h

+1 −1
Original line number Diff line number Diff line
@@ -55,7 +55,7 @@ void nfsd_file_cache_shutdown(void); 
int nfsd_file_cache_start_net(struct net *net);

void nfsd_file_cache_shutdown_net(struct net *net);

void nfsd_file_put(struct nfsd_file *nf);

void nfsd_file_put_local(struct nfsd_file *nf);

struct net *nfsd_file_put_local(struct nfsd_file *nf);

struct nfsd_file *nfsd_file_get(struct nfsd_file *nf);

struct file *nfsd_file_file(struct nfsd_file *nf);

void nfsd_file_close_inode_sync(struct inode *inode);

include/linux/nfslocalio.h

+15 −3
Original line number Diff line number Diff line
@@ -55,7 +55,7 @@ struct nfsd_localio_operations { 
						const struct cred *,

						const struct nfs_fh *,

						const fmode_t);

	void (*nfsd_file_put_local)(struct nfsd_file *);

	struct net *(*nfsd_file_put_local)(struct nfsd_file *);

	struct file *(*nfsd_file_file)(struct nfsd_file *);

} ____cacheline_aligned;
@@ -66,7 +66,7 @@ struct nfsd_file *nfs_open_local_fh(nfs_uuid_t *, 
		   struct rpc_clnt *, const struct cred *,

		   const struct nfs_fh *, const fmode_t);



static inline void nfs_to_nfsd_file_put_local(struct nfsd_file *localio)

static inline void nfs_to_nfsd_net_put(struct net *net)

{

	/*

	 * Once reference to nfsd_serv is dropped, NFSD could be
@@ -74,10 +74,22 @@ static inline void nfs_to_nfsd_file_put_local(struct nfsd_file *localio) 
	 * by always taking RCU.

	 */

	rcu_read_lock();

	nfs_to->nfsd_file_put_local(localio);

	nfs_to->nfsd_serv_put(net);

	rcu_read_unlock();

}



static inline void nfs_to_nfsd_file_put_local(struct nfsd_file *localio)

{

	/*

	 * Must not hold RCU otherwise nfsd_file_put() can easily trigger:

	 * "Voluntary context switch within RCU read-side critical section!"

	 * by scheduling deep in underlying filesystem (e.g. XFS).

	 */

	struct net *net = nfs_to->nfsd_file_put_local(localio);



	nfs_to_nfsd_net_put(net);

}



#else   /* CONFIG_NFS_LOCALIO */

static inline void nfsd_localio_ops_init(void)

{