Return-Path: Received: from mx2.netapp.com ([216.240.18.37]:7880 "EHLO mx2.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751455Ab0LVEA7 (ORCPT ); Tue, 21 Dec 2010 23:00:59 -0500 From: Fred Isaman To: linux-nfs@vger.kernel.org Cc: Trond Myklebust Subject: [PATCH 05/15] pnfs: change layout state seqlock to a spinlock Date: Tue, 21 Dec 2010 23:00:39 -0500 Message-Id: <1292990449-20057-6-git-send-email-iisaman@netapp.com> In-Reply-To: <1292990449-20057-1-git-send-email-iisaman@netapp.com> References: <1292990449-20057-1-git-send-email-iisaman@netapp.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: Content-Type: text/plain MIME-Version: 1.0 This prepares for future changes, where the layout state needs to change atomically with several other variables. In particular, it will need to know if lo->segs is empty, as we test that instead of manipulating the NFS_LAYOUT_STATEID_SET bit. Moreover, the layoutstateid is not really a read-mostly structure, as it is written almost as often as it is read. The behavior of pnfs_get_layout_stateid is also slightly changed, so that it no longer changes the stateid. Its name is changed to +pnfs_choose_layoutget_stateid. Signed-off-by: Fred Isaman Signed-off-by: Benny Halevy --- fs/nfs/nfs4xdr.c | 2 +- fs/nfs/pnfs.c | 79 +++++++++++++++-------------------------------------- fs/nfs/pnfs.h | 7 ++--- 3 files changed, 27 insertions(+), 61 deletions(-) diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c index f3f9915..4e28242 100644 --- a/fs/nfs/nfs4xdr.c +++ b/fs/nfs/nfs4xdr.c @@ -1798,7 +1798,7 @@ encode_layoutget(struct xdr_stream *xdr, p = xdr_encode_hyper(p, args->range.offset); p = xdr_encode_hyper(p, args->range.length); p = xdr_encode_hyper(p, args->minlength); - pnfs_get_layout_stateid(&stateid, NFS_I(args->inode)->layout, + pnfs_choose_layoutget_stateid(&stateid, NFS_I(args->inode)->layout, args->ctx->state); p = xdr_encode_opaque_fixed(p, &stateid.data, NFS4_STATEID_SIZE); *p = cpu_to_be32(args->maxcount); diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c index 6736f9e..08313f53 100644 --- a/fs/nfs/pnfs.c +++ b/fs/nfs/pnfs.c @@ -258,9 +258,6 @@ pnfs_clear_lseg_list(struct pnfs_layout_hdr *lo, struct list_head *tmp_list) /* List does not take a reference, so no need for put here */ list_del_init(&lo->plh_layouts); spin_unlock(&clp->cl_lock); - write_seqlock(&lo->plh_seqlock); - clear_bit(NFS_LAYOUT_STATEID_SET, &lo->plh_flags); - write_sequnlock(&lo->plh_seqlock); dprintk("%s:Return\n", __func__); } @@ -319,69 +316,40 @@ pnfs_destroy_all_layouts(struct nfs_client *clp) } } -/* update lo->plh_stateid with new if is more recent - * - * lo->plh_stateid could be the open stateid, in which case we just use what given. - */ +/* update lo->plh_stateid with new if is more recent */ static void pnfs_set_layout_stateid(struct pnfs_layout_hdr *lo, const nfs4_stateid *new) { - nfs4_stateid *old = &lo->plh_stateid; - bool overwrite = false; - - write_seqlock(&lo->plh_seqlock); - if (!test_bit(NFS_LAYOUT_STATEID_SET, &lo->plh_flags) || - memcmp(old->stateid.other, new->stateid.other, sizeof(new->stateid.other))) - overwrite = true; - else { - u32 oldseq, newseq; - - oldseq = be32_to_cpu(old->stateid.seqid); - newseq = be32_to_cpu(new->stateid.seqid); - if ((int)(newseq - oldseq) > 0) - overwrite = true; - } - if (overwrite) - memcpy(&old->stateid, &new->stateid, sizeof(new->stateid)); - write_sequnlock(&lo->plh_seqlock); -} - -static void -pnfs_layout_from_open_stateid(struct pnfs_layout_hdr *lo, - struct nfs4_state *state) -{ - int seq; + u32 oldseq, newseq; - dprintk("--> %s\n", __func__); - write_seqlock(&lo->plh_seqlock); - do { - seq = read_seqbegin(&state->seqlock); - memcpy(lo->plh_stateid.data, state->stateid.data, - sizeof(state->stateid.data)); - } while (read_seqretry(&state->seqlock, seq)); - set_bit(NFS_LAYOUT_STATEID_SET, &lo->plh_flags); - write_sequnlock(&lo->plh_seqlock); - dprintk("<-- %s\n", __func__); + oldseq = be32_to_cpu(lo->plh_stateid.stateid.seqid); + newseq = be32_to_cpu(new->stateid.seqid); + if ((int)(newseq - oldseq) > 0) + memcpy(&lo->plh_stateid, &new->stateid, sizeof(new->stateid)); } -void -pnfs_get_layout_stateid(nfs4_stateid *dst, struct pnfs_layout_hdr *lo, - struct nfs4_state *open_state) +int +pnfs_choose_layoutget_stateid(nfs4_stateid *dst, struct pnfs_layout_hdr *lo, + struct nfs4_state *open_state) { - int seq; + int status = 0; dprintk("--> %s\n", __func__); - do { - seq = read_seqbegin(&lo->plh_seqlock); - if (!test_bit(NFS_LAYOUT_STATEID_SET, &lo->plh_flags)) { - /* This will trigger retry of the read */ - pnfs_layout_from_open_stateid(lo, open_state); - } else - memcpy(dst->data, lo->plh_stateid.data, - sizeof(lo->plh_stateid.data)); - } while (read_seqretry(&lo->plh_seqlock, seq)); + spin_lock(&lo->plh_inode->i_lock); + if (list_empty(&lo->plh_segs)) { + int seq; + + do { + seq = read_seqbegin(&open_state->seqlock); + memcpy(dst->data, open_state->stateid.data, + sizeof(open_state->stateid.data)); + } while (read_seqretry(&open_state->seqlock, seq)); + } else + memcpy(dst->data, lo->plh_stateid.data, sizeof(lo->plh_stateid.data)); + spin_unlock(&lo->plh_inode->i_lock); dprintk("<-- %s\n", __func__); + return status; } /* @@ -496,7 +464,6 @@ alloc_init_layout_hdr(struct inode *ino) lo->plh_refcount = 1; INIT_LIST_HEAD(&lo->plh_layouts); INIT_LIST_HEAD(&lo->plh_segs); - seqlock_init(&lo->plh_seqlock); lo->plh_inode = ino; return lo; } diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h index c2f1086..1093720 100644 --- a/fs/nfs/pnfs.h +++ b/fs/nfs/pnfs.h @@ -44,7 +44,6 @@ struct pnfs_layout_segment { enum { NFS_LAYOUT_RO_FAILED = 0, /* get ro layout failed stop trying */ NFS_LAYOUT_RW_FAILED, /* get rw layout failed stop trying */ - NFS_LAYOUT_STATEID_SET, /* have a valid layout stateid */ }; /* Per-layout driver specific registration structure */ @@ -63,7 +62,6 @@ struct pnfs_layout_hdr { unsigned long plh_refcount; struct list_head plh_layouts; /* other client layouts */ struct list_head plh_segs; /* layout segments list */ - seqlock_t plh_seqlock; /* Protects the stateid */ nfs4_stateid plh_stateid; unsigned long plh_flags; struct inode *plh_inode; @@ -143,8 +141,9 @@ int pnfs_layout_process(struct nfs4_layoutget *lgp); void pnfs_destroy_layout(struct nfs_inode *); void pnfs_destroy_all_layouts(struct nfs_client *); void put_layout_hdr(struct inode *inode); -void pnfs_get_layout_stateid(nfs4_stateid *dst, struct pnfs_layout_hdr *lo, - struct nfs4_state *open_state); +int pnfs_choose_layoutget_stateid(nfs4_stateid *dst, + struct pnfs_layout_hdr *lo, + struct nfs4_state *open_state); static inline int lo_fail_bit(u32 iomode) -- 1.7.2.1