dcache.c

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/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * dcache.c
 *
 * dentry cache handling code
 *
 * Copyright (C) 2002, 2004 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This program 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 this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/fs.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/namei.h>

#include <cluster/masklog.h>

#include "ocfs2.h"

#include "alloc.h"
#include "dcache.h"
#include "dlmglue.h"
#include "file.h"
#include "inode.h"
#include "super.h"
#include "ocfs2_trace.h"

void ocfs2_dentry_attach_gen(struct dentry *dentry)
{
    unsigned long gen =
        OCFS2_I(dentry->d_parent->d_inode)->ip_dir_lock_gen;
    BUG_ON(dentry->d_inode);
    dentry->d_fsdata = (void *)gen;
}


static int ocfs2_dentry_revalidate(struct dentry *dentry, unsigned int flags)
{
    struct inode *inode;
    int ret = 0;    /* if all else fails, just return false */
    struct ocfs2_super *osb;

    if (flags & LOOKUP_RCU)
        return -ECHILD;

    inode = dentry->d_inode;
    osb = OCFS2_SB(dentry->d_sb);

    trace_ocfs2_dentry_revalidate(dentry, dentry->d_name.len,
                      dentry->d_name.name);

    /* For a negative dentry -
     * check the generation number of the parent and compare with the
     * one stored in the inode.
     */
    if (inode == NULL) {
        unsigned long gen = (unsigned long) dentry->d_fsdata;
        unsigned long pgen =
            OCFS2_I(dentry->d_parent->d_inode)->ip_dir_lock_gen;

        trace_ocfs2_dentry_revalidate_negative(dentry->d_name.len,
                               dentry->d_name.name,
                               pgen, gen);
        if (gen != pgen)
            goto bail;
        goto valid;
    }

    BUG_ON(!osb);

    if (inode == osb->root_inode || is_bad_inode(inode))
        goto bail;

    spin_lock(&OCFS2_I(inode)->ip_lock);
    /* did we or someone else delete this inode? */
    if (OCFS2_I(inode)->ip_flags & OCFS2_INODE_DELETED) {
        spin_unlock(&OCFS2_I(inode)->ip_lock);
        trace_ocfs2_dentry_revalidate_delete(
                (unsigned long long)OCFS2_I(inode)->ip_blkno);
        goto bail;
    }
    spin_unlock(&OCFS2_I(inode)->ip_lock);

    /*
     * We don't need a cluster lock to test this because once an
     * inode nlink hits zero, it never goes back.
     */
    if (inode->i_nlink == 0) {
        trace_ocfs2_dentry_revalidate_orphaned(
            (unsigned long long)OCFS2_I(inode)->ip_blkno,
            S_ISDIR(inode->i_mode));
        goto bail;
    }

    /*
     * If the last lookup failed to create dentry lock, let us
     * redo it.
     */
    if (!dentry->d_fsdata) {
        trace_ocfs2_dentry_revalidate_nofsdata(
                (unsigned long long)OCFS2_I(inode)->ip_blkno);
        goto bail;
    }

valid:
    ret = 1;

bail:
    trace_ocfs2_dentry_revalidate_ret(ret);
    return ret;
}

static int ocfs2_match_dentry(struct dentry *dentry,
                  u64 parent_blkno,
                  int skip_unhashed)
{
    struct inode *parent;

    /*
     * ocfs2_lookup() does a d_splice_alias() _before_ attaching
     * to the lock data, so we skip those here, otherwise
     * ocfs2_dentry_attach_lock() will get its original dentry
     * back.
     */
    if (!dentry->d_fsdata)
        return 0;

    if (!dentry->d_parent)
        return 0;

    if (skip_unhashed && d_unhashed(dentry))
        return 0;

    parent = dentry->d_parent->d_inode;
    /* Negative parent dentry? */
    if (!parent)
        return 0;

    /* Name is in a different directory. */
    if (OCFS2_I(parent)->ip_blkno != parent_blkno)
        return 0;

    return 1;
}

/*
 * Walk the inode alias list, and find a dentry which has a given
 * parent. ocfs2_dentry_attach_lock() wants to find _any_ alias as it
 * is looking for a dentry_lock reference. The downconvert thread is
 * looking to unhash aliases, so we allow it to skip any that already
 * have that property.
 */
struct dentry *ocfs2_find_local_alias(struct inode *inode,
                      u64 parent_blkno,
                      int skip_unhashed)
{
    struct hlist_node *p;
    struct dentry *dentry;

    spin_lock(&inode->i_lock);
    hlist_for_each_entry(dentry, p, &inode->i_dentry, d_alias) {
        spin_lock(&dentry->d_lock);
        if (ocfs2_match_dentry(dentry, parent_blkno, skip_unhashed)) {
            trace_ocfs2_find_local_alias(dentry->d_name.len,
                             dentry->d_name.name);

            dget_dlock(dentry);
            spin_unlock(&dentry->d_lock);
            spin_unlock(&inode->i_lock);
            return dentry;
        }
        spin_unlock(&dentry->d_lock);
    }
    spin_unlock(&inode->i_lock);
    return NULL;
}

DEFINE_SPINLOCK(dentry_attach_lock);

/*
 * Attach this dentry to a cluster lock.
 *
 * Dentry locks cover all links in a given directory to a particular
 * inode. We do this so that ocfs2 can build a lock name which all
 * nodes in the cluster can agree on at all times. Shoving full names
 * in the cluster lock won't work due to size restrictions. Covering
 * links inside of a directory is a good compromise because it still
 * allows us to use the parent directory lock to synchronize
 * operations.
 *
 * Call this function with the parent dir semaphore and the parent dir
 * cluster lock held.
 *
 * The dir semaphore will protect us from having to worry about
 * concurrent processes on our node trying to attach a lock at the
 * same time.
 *
 * The dir cluster lock (held at either PR or EX mode) protects us
 * from unlink and rename on other nodes.
 *
 * A dput() can happen asynchronously due to pruning, so we cover
 * attaching and detaching the dentry lock with a
 * dentry_attach_lock.
 *
 * A node which has done lookup on a name retains a protected read
 * lock until final dput. If the user requests and unlink or rename,
 * the protected read is upgraded to an exclusive lock. Other nodes
 * who have seen the dentry will then be informed that they need to
 * downgrade their lock, which will involve d_delete on the
 * dentry. This happens in ocfs2_dentry_convert_worker().
 */
int ocfs2_dentry_attach_lock(struct dentry *dentry,
                 struct inode *inode,
                 u64 parent_blkno)
{
    int ret;
    struct dentry *alias;
    struct ocfs2_dentry_lock *dl = dentry->d_fsdata;

    trace_ocfs2_dentry_attach_lock(dentry->d_name.len, dentry->d_name.name,
                       (unsigned long long)parent_blkno, dl);

    /*
     * Negative dentry. We ignore these for now.
     *
     * XXX: Could we can improve ocfs2_dentry_revalidate() by
     * tracking these?
     */
    if (!inode)
        return 0;

    if (!dentry->d_inode && dentry->d_fsdata) {
        /* Converting a negative dentry to positive
           Clear dentry->d_fsdata */
        dentry->d_fsdata = dl = NULL;
    }

    if (dl) {
        mlog_bug_on_msg(dl->dl_parent_blkno != parent_blkno,
                " \"%.*s\": old parent: %llu, new: %llu\n",
                dentry->d_name.len, dentry->d_name.name,
                (unsigned long long)parent_blkno,
                (unsigned long long)dl->dl_parent_blkno);
        return 0;
    }

    alias = ocfs2_find_local_alias(inode, parent_blkno, 0);
    if (alias) {
        /*
         * Great, an alias exists, which means we must have a
         * dentry lock already. We can just grab the lock off
         * the alias and add it to the list.
         *
         * We're depending here on the fact that this dentry
         * was found and exists in the dcache and so must have
         * a reference to the dentry_lock because we can't
         * race creates. Final dput() cannot happen on it
         * since we have it pinned, so our reference is safe.
         */
        dl = alias->d_fsdata;
        mlog_bug_on_msg(!dl, "parent %llu, ino %llu\n",
                (unsigned long long)parent_blkno,
                (unsigned long long)OCFS2_I(inode)->ip_blkno);

        mlog_bug_on_msg(dl->dl_parent_blkno != parent_blkno,
                " \"%.*s\": old parent: %llu, new: %llu\n",
                dentry->d_name.len, dentry->d_name.name,
                (unsigned long long)parent_blkno,
                (unsigned long long)dl->dl_parent_blkno);

        trace_ocfs2_dentry_attach_lock_found(dl->dl_lockres.l_name,
                (unsigned long long)parent_blkno,
                (unsigned long long)OCFS2_I(inode)->ip_blkno);

        goto out_attach;
    }

    /*
     * There are no other aliases
     */
    dl = kmalloc(sizeof(*dl), GFP_NOFS);
    if (!dl) {
        ret = -ENOMEM;
        mlog_errno(ret);
        return ret;
    }

    dl->dl_count = 0;
    /*
     * Does this have to happen below, for all attaches, in case
     * the struct inode gets blown away by the downconvert thread?
     */
    dl->dl_inode = igrab(inode);
    dl->dl_parent_blkno = parent_blkno;
    ocfs2_dentry_lock_res_init(dl, parent_blkno, inode);

out_attach:
    spin_lock(&dentry_attach_lock);
    dentry->d_fsdata = dl;
    dl->dl_count++;
    spin_unlock(&dentry_attach_lock);

    /*
     * This actually gets us our PRMODE level lock. From now on,
     * we'll have a notification if one of these names is
     * destroyed on another node.
     */
    ret = ocfs2_dentry_lock(dentry, 0);
    if (!ret)
        ocfs2_dentry_unlock(dentry, 0);
    else
        mlog_errno(ret);

    /*
     * In case of error, manually free the allocation and do the iput().
     * We need to do this because error here means no d_instantiate(),
     * which means iput() will not be called during dput(dentry).
     */
    if (ret < 0 && !alias) {
        ocfs2_lock_res_free(&dl->dl_lockres);
        BUG_ON(dl->dl_count != 1);
        spin_lock(&dentry_attach_lock);
        dentry->d_fsdata = NULL;
        spin_unlock(&dentry_attach_lock);
        kfree(dl);
        iput(inode);
    }

    dput(alias);

    return ret;
}

DEFINE_SPINLOCK(dentry_list_lock);

/* We limit the number of dentry locks to drop in one go. We have
 * this limit so that we don't starve other users of ocfs2_wq. */
#define DL_INODE_DROP_COUNT 64

/* Drop inode references from dentry locks */
static void __ocfs2_drop_dl_inodes(struct ocfs2_super *osb, int drop_count)
{
    struct ocfs2_dentry_lock *dl;

    spin_lock(&dentry_list_lock);
    while (osb->dentry_lock_list && (drop_count < 0 || drop_count--)) {
        dl = osb->dentry_lock_list;
        osb->dentry_lock_list = dl->dl_next;
        spin_unlock(&dentry_list_lock);
        iput(dl->dl_inode);
        kfree(dl);
        spin_lock(&dentry_list_lock);
    }
    spin_unlock(&dentry_list_lock);
}

void ocfs2_drop_dl_inodes(struct work_struct *work)
{
    struct ocfs2_super *osb = container_of(work, struct ocfs2_super,
                           dentry_lock_work);

    __ocfs2_drop_dl_inodes(osb, DL_INODE_DROP_COUNT);
    /*
     * Don't queue dropping if umount is in progress. We flush the
     * list in ocfs2_dismount_volume
     */
    spin_lock(&dentry_list_lock);
    if (osb->dentry_lock_list &&
        !ocfs2_test_osb_flag(osb, OCFS2_OSB_DROP_DENTRY_LOCK_IMMED))
        queue_work(ocfs2_wq, &osb->dentry_lock_work);
    spin_unlock(&dentry_list_lock);
}

/* Flush the whole work queue */
void ocfs2_drop_all_dl_inodes(struct ocfs2_super *osb)
{
    __ocfs2_drop_dl_inodes(osb, -1);
}

/*
 * ocfs2_dentry_iput() and friends.
 *
 * At this point, our particular dentry is detached from the inodes
 * alias list, so there's no way that the locking code can find it.
 *
 * The interesting stuff happens when we determine that our lock needs
 * to go away because this is the last subdir alias in the
 * system. This function needs to handle a couple things:
 *
 * 1) Synchronizing lock shutdown with the downconvert threads. This
 *    is already handled for us via the lockres release drop function
 *    called in ocfs2_release_dentry_lock()
 *
 * 2) A race may occur when we're doing our lock shutdown and
 *    another process wants to create a new dentry lock. Right now we
 *    let them race, which means that for a very short while, this
 *    node might have two locks on a lock resource. This should be a
 *    problem though because one of them is in the process of being
 *    thrown out.
 */
static void ocfs2_drop_dentry_lock(struct ocfs2_super *osb,
                   struct ocfs2_dentry_lock *dl)
{
    ocfs2_simple_drop_lockres(osb, &dl->dl_lockres);
    ocfs2_lock_res_free(&dl->dl_lockres);

    /* We leave dropping of inode reference to ocfs2_wq as that can
     * possibly lead to inode deletion which gets tricky */
    spin_lock(&dentry_list_lock);
    if (!osb->dentry_lock_list &&
        !ocfs2_test_osb_flag(osb, OCFS2_OSB_DROP_DENTRY_LOCK_IMMED))
        queue_work(ocfs2_wq, &osb->dentry_lock_work);
    dl->dl_next = osb->dentry_lock_list;
    osb->dentry_lock_list = dl;
    spin_unlock(&dentry_list_lock);
}

void ocfs2_dentry_lock_put(struct ocfs2_super *osb,
               struct ocfs2_dentry_lock *dl)
{
    int unlock;

    BUG_ON(dl->dl_count == 0);

    spin_lock(&dentry_attach_lock);
    dl->dl_count--;
    unlock = !dl->dl_count;
    spin_unlock(&dentry_attach_lock);

    if (unlock)
        ocfs2_drop_dentry_lock(osb, dl);
}

static void ocfs2_dentry_iput(struct dentry *dentry, struct inode *inode)
{
    struct ocfs2_dentry_lock *dl = dentry->d_fsdata;

    if (!dl) {
        /*
         * No dentry lock is ok if we're disconnected or
         * unhashed.
         */
        if (!(dentry->d_flags & DCACHE_DISCONNECTED) &&
            !d_unhashed(dentry)) {
            unsigned long long ino = 0ULL;
            if (inode)
                ino = (unsigned long long)OCFS2_I(inode)->ip_blkno;
            mlog(ML_ERROR, "Dentry is missing cluster lock. "
                 "inode: %llu, d_flags: 0x%x, d_name: %.*s\n",
                 ino, dentry->d_flags, dentry->d_name.len,
                 dentry->d_name.name);
        }

        goto out;
    }

    mlog_bug_on_msg(dl->dl_count == 0, "dentry: %.*s, count: %u\n",
            dentry->d_name.len, dentry->d_name.name,
            dl->dl_count);

    ocfs2_dentry_lock_put(OCFS2_SB(dentry->d_sb), dl);

out:
    iput(inode);
}

/*
 * d_move(), but keep the locks in sync.
 *
 * When we are done, "dentry" will have the parent dir and name of
 * "target", which will be thrown away.
 *
 * We manually update the lock of "dentry" if need be.
 *
 * "target" doesn't have it's dentry lock touched - we allow the later
 * dput() to handle this for us.
 *
 * This is called during ocfs2_rename(), while holding parent
 * directory locks. The dentries have already been deleted on other
 * nodes via ocfs2_remote_dentry_delete().
 *
 * Normally, the VFS handles the d_move() for the file system, after
 * the ->rename() callback. OCFS2 wants to handle this internally, so
 * the new lock can be created atomically with respect to the cluster.
 */
void ocfs2_dentry_move(struct dentry *dentry, struct dentry *target,
               struct inode *old_dir, struct inode *new_dir)
{
    int ret;
    struct ocfs2_super *osb = OCFS2_SB(old_dir->i_sb);
    struct inode *inode = dentry->d_inode;

    /*
     * Move within the same directory, so the actual lock info won't
     * change.
     *
     * XXX: Is there any advantage to dropping the lock here?
     */
    if (old_dir == new_dir)
        goto out_move;

    ocfs2_dentry_lock_put(osb, dentry->d_fsdata);

    dentry->d_fsdata = NULL;
    ret = ocfs2_dentry_attach_lock(dentry, inode, OCFS2_I(new_dir)->ip_blkno);
    if (ret)
        mlog_errno(ret);

out_move:
    d_move(dentry, target);
}

const struct dentry_operations ocfs2_dentry_ops = {
    .d_revalidate       = ocfs2_dentry_revalidate,
    .d_iput         = ocfs2_dentry_iput,
};