statahead.c

lustre 1.6.5 source code

/* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
 * vim:expandtab:shiftwidth=8:tabstop=8:
 *
 *  Copyright (c) 2007 Cluster File Systems, Inc.
 *
 *   This file is part of Lustre, http://www.lustre.org.
 *
 *   Lustre is free software; you can redistribute it and/or
 *   modify it under the terms of version 2 of the GNU General Public
 *   License as published by the Free Software Foundation.
 *
 *   Lustre is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with Lustre; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp_lock.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>

#define DEBUG_SUBSYSTEM S_LLITE

#include <obd_support.h>
#include <lustre_lite.h>
#include <lustre_dlm.h>
#include <linux/lustre_version.h>
#include "llite_internal.h"

struct ll_sai_entry {
        struct list_head        se_list;
        unsigned int            se_index;
        int                     se_stat;
};

enum {
        SA_ENTRY_UNSTATED = 0,
        SA_ENTRY_STATED
};

static unsigned int sai_generation = 0;
static spinlock_t sai_generation_lock = SPIN_LOCK_UNLOCKED;

static struct ll_statahead_info *ll_sai_alloc(void)
{
        struct ll_statahead_info *sai;

        OBD_ALLOC_PTR(sai);
        if (!sai)
                return NULL;

        spin_lock(&sai_generation_lock);
        sai->sai_generation = ++sai_generation;
        if (unlikely(sai_generation == 0))
                sai->sai_generation = ++sai_generation;
        spin_unlock(&sai_generation_lock);
        atomic_set(&sai->sai_refcount, 1);
        sai->sai_max = LL_SA_RPC_MIN;
        cfs_waitq_init(&sai->sai_waitq);
        cfs_waitq_init(&sai->sai_thread.t_ctl_waitq);
        CFS_INIT_LIST_HEAD(&sai->sai_entries);
        return sai;
}

static inline 
struct ll_statahead_info *ll_sai_get(struct ll_statahead_info *sai)
{
        LASSERT(sai);
        atomic_inc(&sai->sai_refcount);
        return sai;
}

static void ll_sai_put(struct ll_statahead_info *sai)
{
        struct inode         *inode = sai->sai_inode;
        struct ll_inode_info *lli = ll_i2info(inode);
        ENTRY;

        if (atomic_dec_and_lock(&sai->sai_refcount, &lli->lli_lock)) {
                struct ll_sai_entry *entry, *next;

                lli->lli_sai = NULL;
                spin_unlock(&lli->lli_lock);

                LASSERT(sai->sai_thread.t_flags & SVC_STOPPED);

                if (sai->sai_sent > sai->sai_replied)
                        CDEBUG(D_READA,"statahead for dir %lu/%u does not "
                              "finish: [sent:%u] [replied:%u]\n",
                              inode->i_ino, inode->i_generation,
                              sai->sai_sent, sai->sai_replied);

                list_for_each_entry_safe(entry, next, &sai->sai_entries,
                                         se_list) {
                        list_del(&entry->se_list);
                        OBD_FREE_PTR(entry);
                }
                OBD_FREE_PTR(sai);
                iput(inode);
        }
        EXIT;
}

static struct ll_sai_entry *
ll_sai_entry_get(struct ll_statahead_info *sai, unsigned int index, int stat)
{
        struct ll_inode_info *lli = ll_i2info(sai->sai_inode);
        struct ll_sai_entry  *entry;
        ENTRY;

        OBD_ALLOC_PTR(entry);
        if (entry == NULL)
                RETURN(ERR_PTR(-ENOMEM));
        
        CDEBUG(D_READA, "alloc sai entry %p index %u, stat %d\n",
               entry, index, stat);
        entry->se_index = index;
        entry->se_stat  = stat;

        spin_lock(&lli->lli_lock);
        list_add_tail(&entry->se_list, &sai->sai_entries);
        spin_unlock(&lli->lli_lock);

        RETURN(entry);
}

/*
 * inside lli_lock
 * return value:
 *  0: can not find the entry with the index
 *  1: it is the first entry
 *  2: it is not the first entry
 */
static int
ll_sai_entry_set(struct ll_statahead_info *sai, unsigned int index, int stat)
{
        struct ll_sai_entry *entry;
        int                  rc = 0;
        ENTRY;

        if (list_empty(&sai->sai_entries))
                RETURN(0);

        entry = list_entry(sai->sai_entries.next, struct ll_sai_entry, se_list);
        if (entry->se_index == index)
                GOTO(out, rc = 1);

        while (entry->se_list.next != &sai->sai_entries &&
               entry->se_index < index) {
                entry = list_entry(entry->se_list.next, struct ll_sai_entry,
                                   se_list);
                if (entry->se_index == index)
                        GOTO(out, rc = 2);
        }

        EXIT;

out:
        if (rc) {
                LASSERT(entry->se_stat == SA_ENTRY_UNSTATED);
                entry->se_stat = stat;
        }

        return rc;
}

/*
 * Check whether first entry was stated already or not.
 * No need to hold lli_lock, for:
 * (1) it is me that remove entry from the list
 * (2) the statahead thread only add new entry to the list tail
 */
static int ll_sai_entry_stated(struct ll_statahead_info *sai)
{
        struct ll_sai_entry  *entry;
        int                   rc = 0;
        ENTRY;

        if (!list_empty(&sai->sai_entries)) {
                entry = list_entry(sai->sai_entries.next, struct ll_sai_entry,
                                   se_list);
                rc = (entry->se_stat != SA_ENTRY_UNSTATED);
        }

        RETURN(rc);
}

static void ll_sai_entry_put(struct ll_statahead_info *sai)
{
        struct ll_inode_info *lli = ll_i2info(sai->sai_inode);
        struct ll_sai_entry  *entry;
        ENTRY;
        
        spin_lock(&lli->lli_lock);
        if (!list_empty(&sai->sai_entries)) {
                entry = list_entry(sai->sai_entries.next,
                                   struct ll_sai_entry, se_list);
                list_del(&entry->se_list);
                OBD_FREE_PTR(entry);
        }
        spin_unlock(&lli->lli_lock);

        EXIT;
}

/* finish lookup/revalidate */
static int ll_statahead_interpret(struct obd_export *exp,
                                  struct ptlrpc_request *req,
                                  struct md_enqueue_info *minfo,
                                  int rc)
{
        struct lookup_intent     *it = &minfo->mi_it;
        struct dentry            *dentry = minfo->mi_dentry;
        struct inode             *dir = dentry->d_parent->d_inode;
        struct ll_inode_info     *lli = ll_i2info(dir);
        struct ll_statahead_info *sai = NULL;
        ENTRY;

        CDEBUG(D_READA, "interpret statahead %.*s rc %d\n",
               dentry->d_name.len, dentry->d_name.name, rc);

        spin_lock(&lli->lli_lock);
        if (unlikely(lli->lli_sai == NULL ||
            lli->lli_sai->sai_generation != minfo->mi_generation)) {
                spin_unlock(&lli->lli_lock);
                GOTO(out_free, rc = -ESTALE);
        } else {
                sai = ll_sai_get(lli->lli_sai);
                spin_unlock(&lli->lli_lock);
        }

        if (rc || dir == NULL)
                GOTO(out, rc);

        if (dentry->d_inode == NULL) {
                /* lookup */
                struct dentry    *save = dentry;
                struct it_cb_data icbd = {
                        .icbd_parent   = dir,
                        .icbd_childp   = &dentry
                };

                rc = lookup_it_finish(req, DLM_REPLY_REC_OFF, it, &icbd);
                if (!rc)
                        /* 
                         * Here dentry->d_inode might be NULL,
                         * because the entry may have been removed before
                         * we start doing stat ahead.
                         */
                        ll_lookup_finish_locks(it, dentry);

                if (dentry != save)
                        dput(save);
        } else {
                /* revalidate */
                struct mds_body *body;

                body = lustre_msg_buf(req->rq_repmsg, DLM_REPLY_REC_OFF,
                                      sizeof(*body));
                if (memcmp(&minfo->mi_data.fid2, &body->fid1,
                           sizeof(body->fid1))) {
                        ll_unhash_aliases(dentry->d_inode);
                        GOTO(out, rc = -EAGAIN);
                }

                rc = revalidate_it_finish(req, DLM_REPLY_REC_OFF, it, dentry);
                if (rc) {
                        ll_unhash_aliases(dentry->d_inode);
                        GOTO(out, rc);
                }

                spin_lock(&dcache_lock);
                lock_dentry(dentry);
                __d_drop(dentry);
#ifdef DCACHE_LUSTRE_INVALID
                dentry->d_flags &= ~DCACHE_LUSTRE_INVALID;
#endif
                unlock_dentry(dentry);
                d_rehash_cond(dentry, 0);
                spin_unlock(&dcache_lock);

                ll_lookup_finish_locks(it, dentry);
        }
        EXIT;

out:
        if (sai != NULL) {
                int first;

                sai->sai_replied++;
                spin_lock(&lli->lli_lock);
                first = ll_sai_entry_set(sai,
                                         (unsigned int)(long)minfo->mi_cbdata,
                                         SA_ENTRY_STATED);
                /*
                 * wake up the "ls -l" process only when the first entry
                 * returned.
                 */
                spin_unlock(&lli->lli_lock);
                if (first == 1)
                        cfs_waitq_signal(&sai->sai_waitq);
                else if (first == 0)
                        CDEBUG(D_READA, "can't find sai entry for dir "
                               "%lu/%u generation %u index %d\n",
                               dir->i_ino, dir->i_generation,