Return-Path: Received: from mx2.netapp.com ([216.240.18.37]:18993 "EHLO mx2.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755998Ab1AaP1g (ORCPT ); Mon, 31 Jan 2011 10:27:36 -0500 From: Fred Isaman To: linux-nfs@vger.kernel.org Cc: Trond Myklebust Subject: [PATCH 3/3] pnfs: fix pnfs lock inversion of i_lock and cl_lock Date: Mon, 31 Jan 2011 10:27:13 -0500 Message-Id: <1296487633-21057-4-git-send-email-iisaman@netapp.com> In-Reply-To: <1296487633-21057-1-git-send-email-iisaman@netapp.com> References: <1296487633-21057-1-git-send-email-iisaman@netapp.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: Content-Type: text/plain MIME-Version: 1.0 The pnfs code was using throughout the lock order i_lock, cl_lock. This conflicts with the nfs delegation code. Rework the pnfs code to avoid taking both locks simultaneously. Currently the code takes the double lock to add/remove the layout to a nfs_client list, while atomically checking that the list of lsegs is empty. To avoid this, we rely on existing serializations. When a layout is initialized with lseg count equal zero, LAYOUTGET's openstateid serialization is in effect, making it safe to assume it stays zero unless we change it. And once a layout's lseg count drops to zero, it is set as DESTROYED and so will stay at zero. Signed-off-by: Fred Isaman --- fs/nfs/callback_proc.c | 2 +- fs/nfs/pnfs.c | 50 +++++++++++++++++++++++++++-------------------- 2 files changed, 30 insertions(+), 22 deletions(-) diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c index 8958757..2f41dcce 100644 --- a/fs/nfs/callback_proc.c +++ b/fs/nfs/callback_proc.c @@ -188,10 +188,10 @@ static u32 initiate_bulk_draining(struct nfs_client *clp, rv = NFS4ERR_DELAY; list_del_init(&lo->plh_bulk_recall); spin_unlock(&ino->i_lock); + pnfs_free_lseg_list(&free_me_list); put_layout_hdr(lo); iput(ino); } - pnfs_free_lseg_list(&free_me_list); return rv; } diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c index f89c3bb..ee6c69a 100644 --- a/fs/nfs/pnfs.c +++ b/fs/nfs/pnfs.c @@ -247,13 +247,6 @@ put_lseg_locked(struct pnfs_layout_segment *lseg, BUG_ON(test_bit(NFS_LSEG_VALID, &lseg->pls_flags)); list_del(&lseg->pls_list); if (list_empty(&lseg->pls_layout->plh_segs)) { - struct nfs_client *clp; - - clp = NFS_SERVER(ino)->nfs_client; - spin_lock(&clp->cl_lock); - /* List does not take a reference, so no need for put here */ - list_del_init(&lseg->pls_layout->plh_layouts); - spin_unlock(&clp->cl_lock); set_bit(NFS_LAYOUT_DESTROYED, &lseg->pls_layout->plh_flags); /* Matched by initial refcount set in alloc_init_layout_hdr */ put_layout_hdr_locked(lseg->pls_layout); @@ -319,14 +312,30 @@ mark_matching_lsegs_invalid(struct pnfs_layout_hdr *lo, return invalid - removed; } +/* note free_me must contain lsegs from a single layout_hdr */ void pnfs_free_lseg_list(struct list_head *free_me) { - struct pnfs_layout_segment *lseg, *tmp; + if (!list_empty(free_me)) { + struct pnfs_layout_segment *lseg, *tmp; + struct pnfs_layout_hdr *lo; - list_for_each_entry_safe(lseg, tmp, free_me, pls_list) { - list_del(&lseg->pls_list); - free_lseg(lseg); + lo = list_first_entry(free_me, + struct pnfs_layout_segment, + pls_list)->pls_layout; + + if (test_bit(NFS_LAYOUT_DESTROYED, &lo->plh_flags)) { + struct nfs_client *clp; + + clp = NFS_SERVER(lo->plh_inode)->nfs_client; + spin_lock(&clp->cl_lock); + list_del_init(&lo->plh_layouts); + spin_unlock(&clp->cl_lock); + } + list_for_each_entry_safe(lseg, tmp, free_me, pls_list) { + list_del(&lseg->pls_list); + free_lseg(lseg); + } } } @@ -704,6 +713,7 @@ pnfs_update_layout(struct inode *ino, struct nfs_client *clp = NFS_SERVER(ino)->nfs_client; struct pnfs_layout_hdr *lo; struct pnfs_layout_segment *lseg = NULL; + bool first = false; if (!pnfs_enabled_sb(NFS_SERVER(ino))) return NULL; @@ -734,7 +744,10 @@ pnfs_update_layout(struct inode *ino, atomic_inc(&lo->plh_outstanding); get_layout_hdr(lo); - if (list_empty(&lo->plh_segs)) { + if (list_empty(&lo->plh_segs)) + first = true; + spin_unlock(&ino->i_lock); + if (first) { /* The lo must be on the clp list if there is any * chance of a CB_LAYOUTRECALL(FILE) coming in. */ @@ -743,17 +756,12 @@ pnfs_update_layout(struct inode *ino, list_add_tail(&lo->plh_layouts, &clp->cl_layouts); spin_unlock(&clp->cl_lock); } - spin_unlock(&ino->i_lock); lseg = send_layoutget(lo, ctx, iomode); - if (!lseg) { - spin_lock(&ino->i_lock); - if (list_empty(&lo->plh_segs)) { - spin_lock(&clp->cl_lock); - list_del_init(&lo->plh_layouts); - spin_unlock(&clp->cl_lock); - } - spin_unlock(&ino->i_lock); + if (!lseg && first) { + spin_lock(&clp->cl_lock); + list_del_init(&lo->plh_layouts); + spin_unlock(&clp->cl_lock); } atomic_dec(&lo->plh_outstanding); put_layout_hdr(lo); -- 1.7.2.1