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| author |   Florian Westphal <fw@strlen.de> | 2016-08-09 12:16:07 +0200 |
|---|---|---|
| committer |   Steffen Klassert <steffen.klassert@secunet.com> | 2016-08-10 11:23:24 +0200 |
| commit | b65e3d7be06fd8ff5236439254f338fe1a8d4bbd (patch) | |
| tree | e9831de71641f57f8987811bdfd8b74b9cdbb438 /net/xfrm | |
| parent | xfrm: state: delay freeing until rcu grace period has elapsed (diff) | |
| download | linux-dev-b65e3d7be06fd8ff5236439254f338fe1a8d4bbd.tar.xz linux-dev-b65e3d7be06fd8ff5236439254f338fe1a8d4bbd.zip | |
xfrm: state: add sequence count to detect hash resizes
Once xfrm_state_find is lockless we have to cope with a concurrent
resize opertion.
We use a sequence counter to block in case a resize is in progress
and to detect if we might have missed a state that got moved to
a new hash table.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Diffstat (limited to 'net/xfrm')
| -rw-r--r-- | net/xfrm/xfrm_state.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c index 8e373876924f..ac4037cf6a29 100644 --- a/net/xfrm/xfrm_state.c +++ b/net/xfrm/xfrm_state.c @@ -36,6 +36,7 @@ */ static unsigned int xfrm_state_hashmax __read_mostly = 1 * 1024 * 1024; +static __read_mostly seqcount_t xfrm_state_hash_generation = SEQCNT_ZERO(xfrm_state_hash_generation); static inline bool xfrm_state_hold_rcu(struct xfrm_state __rcu *x) { @@ -127,6 +128,7 @@ static void xfrm_hash_resize(struct work_struct *work) } spin_lock_bh(&net->xfrm.xfrm_state_lock); + write_seqcount_begin(&xfrm_state_hash_generation); nhashmask = (nsize / sizeof(struct hlist_head)) - 1U; for (i = net->xfrm.state_hmask; i >= 0; i--) @@ -143,6 +145,7 @@ static void xfrm_hash_resize(struct work_struct *work) net->xfrm.state_byspi = nspi; net->xfrm.state_hmask = nhashmask; + write_seqcount_end(&xfrm_state_hash_generation); spin_unlock_bh(&net->xfrm.xfrm_state_lock); osize = (ohashmask + 1) * sizeof(struct hlist_head); @@ -787,10 +790,13 @@ xfrm_state_find(const xfrm_address_t *daddr, const xfrm_address_t *saddr, struct xfrm_state *best = NULL; u32 mark = pol->mark.v & pol->mark.m; unsigned short encap_family = tmpl->encap_family; + unsigned int sequence; struct km_event c; to_put = NULL; + sequence = read_seqcount_begin(&xfrm_state_hash_generation); + spin_lock_bh(&net->xfrm.xfrm_state_lock); h = xfrm_dst_hash(net, daddr, saddr, tmpl->reqid, encap_family); hlist_for_each_entry_rcu(x, net->xfrm.state_bydst + h, bydst) { @@ -894,6 +900,15 @@ out: spin_unlock_bh(&net->xfrm.xfrm_state_lock); if (to_put) xfrm_state_put(to_put); + + if (read_seqcount_retry(&xfrm_state_hash_generation, sequence)) { + *err = -EAGAIN; + if (x) { + xfrm_state_put(x); + x = NULL; + } + } + return x; } |