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[PATCH v3] NFSd: fix locking in nfsd_forget_delegations() [message #47062] Tue, 03 July 2012 13:01
Stanislav Kinsbursky is currently offline  Stanislav Kinsbursky
Messages: 683
Registered: October 2011
Senior Member
From: *parallels.com
v3: rebased on 3.5-rc3 kernel

v2: dl_recall_lru list is used for delegations collect because it's modified
both in unhash_delegation() and nfsd_break_one_deleg().

This patch adds recall_lock hold to nfsd_forget_delegations() to protect
nfsd_process_n_delegations() call.
Also, looks like it would be better to collect delegations to some local
on-stack list, and then unhash collected list. This split allows to
simplify locking, because delegation traversing is protected by recall_lock,
when delegation unhash is protected by client_mutex.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
---
fs/nfsd/nfs4state.c | 21 +++++++++++++++++----
1 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 59b9efc..33eccee 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4579,7 +4579,7 @@ void nfsd_forget_openowners(u64 num)
printk(KERN_INFO "NFSD: Forgot %d open owners", count);
}

-int nfsd_process_n_delegations(u64 num, void (*deleg_func)(struct nfs4_delegation *))
+int nfsd_process_n_delegations(u64 num, struct list_head *list)
{
int i, count = 0;
struct nfs4_file *fp, *fnext;
@@ -4588,7 +4588,7 @@ int nfsd_process_n_delegations(u64 num, void (*deleg_func)(struct nfs4_delegatio
for (i = 0; i < FILE_HASH_SIZE; i++) {
list_for_each_entry_safe(fp, fnext, &file_hashtbl[i], fi_hash) {
list_for_each_entry_safe(dp, dnext, &fp->fi_delegations, dl_perfile) {
- deleg_func(dp);
+ list_move(&dp->dl_recall_lru, list);
if (++count == num)
return count;
}
@@ -4601,9 +4601,16 @@ int nfsd_process_n_delegations(u64 num, void (*deleg_func)(struct nfs4_delegatio
void nfsd_forget_delegations(u64 num)
{
unsigned int count;
+ LIST_HEAD(victims);
+ struct nfs4_delegation *dp, *dnext;
+
+ spin_lock(&recall_lock);
+ count = nfsd_process_n_delegations(num, &victims);
+ spin_unlock(&recall_lock);

nfs4_lock_state();
- count = nfsd_process_n_delegations(num, unhash_delegation);
+ list_for_each_entry_safe(dp, dnext, &victims, dl_recall_lru)
+ unhash_delegation(dp);
nfs4_unlock_state();

printk(KERN_INFO "NFSD: Forgot %d delegations", count);
@@ -4612,10 +4619,16 @@ void nfsd_forget_delegations(u64 num)
void nfsd_recall_delegations(u64 num)
{
unsigned int count;
+ LIST_HEAD(victims);
+ struct nfs4_delegation *dp, *dnext;

nfs4_lock_state();
spin_lock(&recall_lock);
- count = nfsd_process_n_delegations(num, nfsd_break_one_deleg);
+ count = nfsd_process_n_delegations(num, &victims);
+ list_for_each_entry_safe(dp, dnext, &victims, dl_recall_lru) {
+ list_del(&dp->dl_recall_lru);
+ nfsd_break_one_deleg(dp);
+ }
spin_unlock(&recall_lock);
nfs4_unlock_state();
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