diff options
| -rw-r--r-- | fs/nfsd/nfs4state.c | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index c0d45cec9958..2204e1fe5725 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -41,6 +41,7 @@ #include <linux/ratelimit.h> #include <linux/sunrpc/svcauth_gss.h> #include <linux/sunrpc/addr.h> +#include <linux/hash.h> #include "xdr4.h" #include "xdr4cb.h" #include "vfs.h" @@ -364,6 +365,79 @@ static struct nfs4_ol_stateid * nfs4_alloc_stateid(struct nfs4_client *clp) return openlockstateid(nfs4_alloc_stid(clp, stateid_slab)); } +/* + * When we recall a delegation, we should be careful not to hand it + * out again straight away. + * To ensure this we keep a pair of bloom filters ('new' and 'old') + * in which the filehandles of recalled delegations are "stored". + * If a filehandle appear in either filter, a delegation is blocked. + * When a delegation is recalled, the filehandle is stored in the "new" + * filter. + * Every 30 seconds we swap the filters and clear the "new" one, + * unless both are empty of course. + * + * Each filter is 256 bits. We hash the filehandle to 32bit and use the + * low 3 bytes as hash-table indices. + * + * 'state_lock', which is always held when block_delegations() is called, + * is used to manage concurrent access. Testing does not need the lock + * except when swapping the two filters. + */ +static struct bloom_pair { + int entries, old_entries; + time_t swap_time; + int new; /* index into 'set' */ + DECLARE_BITMAP(set[2], 256); +} blocked_delegations; + +static int delegation_blocked(struct knfsd_fh *fh) +{ + u32 hash; + struct bloom_pair *bd = &blocked_delegations; + + if (bd->entries == 0) + return 0; + if (seconds_since_boot() - bd->swap_time > 30) { + spin_lock(&state_lock); + if (seconds_since_boot() - bd->swap_time > 30) { + bd->entries -= bd->old_entries; + bd->old_entries = bd->entries; + memset(bd->set[bd->new], 0, + sizeof(bd->set[0])); + bd->new = 1-bd->new; + bd->swap_time = seconds_since_boot(); + } + spin_unlock(&state_lock); + } + hash = arch_fast_hash(&fh->fh_base, fh->fh_size, 0); + if (test_bit(hash&255, bd->set[0]) && + test_bit((hash>>8)&255, bd->set[0]) && + test_bit((hash>>16)&255, bd->set[0])) + return 1; + + if (test_bit(hash&255, bd->set[1]) && + test_bit((hash>>8)&255, bd->set[1]) && + test_bit((hash>>16)&255, bd->set[1])) + return 1; + + return 0; +} + +static void block_delegations(struct knfsd_fh *fh) +{ + u32 hash; + struct bloom_pair *bd = &blocked_delegations; + + hash = arch_fast_hash(&fh->fh_base, fh->fh_size, 0); + + __set_bit(hash&255, bd->set[bd->new]); + __set_bit((hash>>8)&255, bd->set[bd->new]); + __set_bit((hash>>16)&255, bd->set[bd->new]); + if (bd->entries == 0) + bd->swap_time = seconds_since_boot(); + bd->entries += 1; +} + static struct nfs4_delegation * alloc_init_deleg(struct nfs4_client *clp, struct nfs4_ol_stateid *stp, struct svc_fh *current_fh) { @@ -372,6 +446,8 @@ alloc_init_deleg(struct nfs4_client *clp, struct nfs4_ol_stateid *stp, struct sv dprintk("NFSD alloc_init_deleg\n"); if (num_delegations > max_delegations) return NULL; + if (delegation_blocked(¤t_fh->fh_handle)) + return NULL; dp = delegstateid(nfs4_alloc_stid(clp, deleg_slab)); if (dp == NULL) return dp; @@ -2770,6 +2846,8 @@ static void nfsd_break_one_deleg(struct nfs4_delegation *dp) /* Only place dl_time is set; protected by i_lock: */ dp->dl_time = get_seconds(); + block_delegations(&dp->dl_fh); + nfsd4_cb_recall(dp); } |