Return-Path: linux-nfs-owner@vger.kernel.org Received: from mx1.redhat.com ([209.132.183.28]:39911 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752864Ab3JBPYR (ORCPT ); Wed, 2 Oct 2013 11:24:17 -0400 Date: Wed, 2 Oct 2013 11:24:15 -0400 From: "J. Bruce Fields" To: Benny Halevy Cc: linux-nfs@vger.kernel.org Subject: Re: [PATCH RFC v0 10/49] pnfsd: use sbid hash table to map super_blocks to devid major identifiers Message-ID: <20131002152415.GC2002@pad.fieldses.org> References: <52447EA0.7070004@primarydata.com> <1380220831-13136-1-git-send-email-bhalevy@primarydata.com> <20131001221433.GB30994@pad.fieldses.org> <524C2E80.8040407@primarydata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <524C2E80.8040407@primarydata.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Wed, Oct 02, 2013 at 05:32:32PM +0300, Benny Halevy wrote: > On 2013-10-02 01:14, J. Bruce Fields wrote: > > See previous comments. What guarantees these superblock pointers stay > > good as long as they're in the cache? > > Currently, the dependency on nfsd.ko should hold them but that should go away. I don't see how that prevents anyone from unmounting a filesystem. > Trying to think about referencing svc_export instead, we use find_sbid_id > to get to the superblock in nfsd4_getdevinfo since we have no current fh. > And we need the superblock to call into the fs sb->s_pnfs_op->get_device_info > later in nfsd4_encode_getdevinfo. > > Just to make sure, we can safely get to the sb via exp->ex_path.dentry->d_inode->i_sb > right? Right. --b. > > Benny > > > > > --b. > > > > On Thu, Sep 26, 2013 at 02:40:31PM -0400, Benny Halevy wrote: > >> From: Benny Halevy > >> > >> Signed-off-by: Benny Halevy > >> [pnfsd: alloc_sid should kmalloc a object not a pointer] > >> Signed-off-by: Bian Naimeng > >> Signed-off-by: Benny Halevy > >> Signed-off-by: Benny Halevy > >> --- > >> fs/nfsd/nfs4pnfsd.c | 120 ++++++++++++++++++++++++++++++++++++++++++++++++++++ > >> fs/nfsd/pnfsd.h | 2 + > >> 2 files changed, 122 insertions(+) > >> > >> diff --git a/fs/nfsd/nfs4pnfsd.c b/fs/nfsd/nfs4pnfsd.c > >> index cb28207..9a7cbc9 100644 > >> --- a/fs/nfsd/nfs4pnfsd.c > >> +++ b/fs/nfsd/nfs4pnfsd.c > >> @@ -25,3 +25,123 @@ > >> > >> #define NFSDDBG_FACILITY NFSDDBG_PNFS > >> > >> +static DEFINE_SPINLOCK(layout_lock); > >> + > >> +/* hash table for nfsd4_pnfs_deviceid.sbid */ > >> +#define SBID_HASH_BITS 8 > >> +#define SBID_HASH_SIZE (1 << SBID_HASH_BITS) > >> +#define SBID_HASH_MASK (SBID_HASH_SIZE - 1) > >> + > >> +struct sbid_tracker { > >> + u64 id; > >> + struct super_block *sb; > >> + struct list_head hash; > >> +}; > >> + > >> +static u64 current_sbid; > >> +static struct list_head sbid_hashtbl[SBID_HASH_SIZE]; > >> + > >> +static unsigned long > >> +sbid_hashval(struct super_block *sb) > >> +{ > >> + return hash_ptr(sb, SBID_HASH_BITS); > >> +} > >> + > >> +static struct sbid_tracker * > >> +alloc_sbid(void) > >> +{ > >> + return kmalloc(sizeof(struct sbid_tracker), GFP_KERNEL); > >> +} > >> + > >> +static void > >> +destroy_sbid(struct sbid_tracker *sbid) > >> +{ > >> + spin_lock(&layout_lock); > >> + list_del(&sbid->hash); > >> + spin_unlock(&layout_lock); > >> + kfree(sbid); > >> +} > >> + > >> +void > >> +nfsd4_free_pnfs_slabs(void) > >> +{ > >> + int i; > >> + struct sbid_tracker *sbid; > >> + > >> + for (i = 0; i < SBID_HASH_SIZE; i++) { > >> + while (!list_empty(&sbid_hashtbl[i])) { > >> + sbid = list_first_entry(&sbid_hashtbl[i], > >> + struct sbid_tracker, > >> + hash); > >> + destroy_sbid(sbid); > >> + } > >> + } > >> +} > >> + > >> +int > >> +nfsd4_init_pnfs_slabs(void) > >> +{ > >> + int i; > >> + > >> + for (i = 0; i < SBID_HASH_SIZE; i++) > >> + INIT_LIST_HEAD(&sbid_hashtbl[i]); > >> + > >> + return 0; > >> +} > >> + > >> +static u64 > >> +alloc_init_sbid(struct super_block *sb) > >> +{ > >> + struct sbid_tracker *sbid; > >> + struct sbid_tracker *new = alloc_sbid(); > >> + unsigned long hash_idx = sbid_hashval(sb); > >> + u64 id = 0; > >> + > >> + if (likely(new)) { > >> + spin_lock(&layout_lock); > >> + id = ++current_sbid; > >> + new->id = (id << SBID_HASH_BITS) | (hash_idx & SBID_HASH_MASK); > >> + id = new->id; > >> + BUG_ON(id == 0); > >> + new->sb = sb; > >> + > >> + list_for_each_entry (sbid, &sbid_hashtbl[hash_idx], hash) > >> + if (sbid->sb == sb) { > >> + kfree(new); > >> + id = sbid->id; > >> + spin_unlock(&layout_lock); > >> + return id; > >> + } > >> + list_add(&new->hash, &sbid_hashtbl[hash_idx]); > >> + spin_unlock(&layout_lock); > >> + } > >> + return id; > >> +} > >> + > >> +static u64 > >> +find_create_sbid(struct super_block *sb) > >> +{ > >> + struct sbid_tracker *sbid; > >> + unsigned long hash_idx = sbid_hashval(sb); > >> + int pos = 0; > >> + u64 id = 0; > >> + > >> + spin_lock(&layout_lock); > >> + list_for_each_entry (sbid, &sbid_hashtbl[hash_idx], hash) { > >> + pos++; > >> + if (sbid->sb != sb) > >> + continue; > >> + if (pos > 1) { > >> + list_del(&sbid->hash); > >> + list_add(&sbid->hash, &sbid_hashtbl[hash_idx]); > >> + } > >> + id = sbid->id; > >> + break; > >> + } > >> + spin_unlock(&layout_lock); > >> + > >> + if (!id) > >> + id = alloc_init_sbid(sb); > >> + > >> + return id; > >> +} > >> diff --git a/fs/nfsd/pnfsd.h b/fs/nfsd/pnfsd.h > >> index 7c46791..29ea2e7 100644 > >> --- a/fs/nfsd/pnfsd.h > >> +++ b/fs/nfsd/pnfsd.h > >> @@ -36,4 +36,6 @@ > >> > >> #include > >> > >> +#include "xdr4.h" > >> + > >> #endif /* LINUX_NFSD_PNFSD_H */ > >> -- > >> 1.8.3.1 > >> > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > >