This is a note to let you know that I've just added the patch titled
nfs_common: must not hold RCU while calling nfsd_file_put_local
to the 6.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nfs_common-must-not-hold-rcu-while-calling-nfsd_file.patch
and it can be found in the queue-6.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 1872d3d40b818f422f3f5efa9add0f9e8eb4bf56
Author: Mike Snitzer <snitzer@xxxxxxxxxx>
Date: Wed Nov 13 22:59:38 2024 -0500
nfs_common: must not hold RCU while calling nfsd_file_put_local
[ Upstream commit c840b8e1f039e90f97ca55525667eb961422f86c ]
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: 65f2a5c36635 ("nfs_common: fix race in NFS calls to nfsd_file_put_local() and nfsd_serv_put()")
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Reviewed-by: NeilBrown <neilb@xxxxxxx>
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/nfs_common/nfslocalio.c b/fs/nfs_common/nfslocalio.c
index 09404d142d1ae..a74ec08f6c96d 100644
--- a/fs/nfs_common/nfslocalio.c
+++ b/fs/nfs_common/nfslocalio.c
@@ -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);
diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index 2e6783f637124..146a9463c3c23 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -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;
}
/**
diff --git a/fs/nfsd/filecache.h b/fs/nfsd/filecache.h
index cadf3c2689c44..d5db6b34ba302 100644
--- a/fs/nfsd/filecache.h
+++ b/fs/nfsd/filecache.h
@@ -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);
diff --git a/include/linux/nfslocalio.h b/include/linux/nfslocalio.h
index 3982fea799195..9202f4b24343d 100644
--- a/include/linux/nfslocalio.h
+++ b/include/linux/nfslocalio.h
@@ -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)
{
