![Eric Dumazet](/assets/img/avatar_default.png)
Some long time ago, dentry struct was carefully tuned so that on 32 bits UP, sizeof(struct dentry) was exactly 128, ie a power of 2, and a multiple of memory cache lines. Then RCU was added and dentry struct enlarged by two pointers, with nice results for SMP, but not so good on UP, because breaking the above tuning (128 + 8 = 136 bytes) This patch reverts this unwanted side effect, by using an union (d_u), where d_rcu and d_child are placed so that these two fields can share their memory needs. At the time d_free() is called (and d_rcu is really used), d_child is known to be empty and not touched by the dentry freeing. Lockless lookups only access d_name, d_parent, d_lock, d_op, d_flags (so the previous content of d_child is not needed if said dentry was unhashed but still accessed by a CPU because of RCU constraints) As dentry cache easily contains millions of entries, a size reduction is worth the extra complexity of the ugly C union. Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Cc: Dipankar Sarma <dipankar@in.ibm.com> Cc: Maneesh Soni <maneesh@in.ibm.com> Cc: Miklos Szeredi <miklos@szeredi.hu> Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Cc: Ian Kent <raven@themaw.net> Cc: Paul Jackson <pj@sgi.com> Cc: Al Viro <viro@ftp.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de> Cc: Trond Myklebust <trond.myklebust@fys.uio.no> Cc: Neil Brown <neilb@cse.unsw.edu.au> Cc: James Morris <jmorris@namei.org> Cc: Stephen Smalley <sds@epoch.ncsc.mil> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
397 lines
8.4 KiB
C
397 lines
8.4 KiB
C
/* -*- c -*- --------------------------------------------------------------- *
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*
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* linux/fs/autofs/inode.c
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*
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* Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
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*
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* This file is part of the Linux kernel and is made available under
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* the terms of the GNU General Public License, version 2, or at your
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* option, any later version, incorporated herein by reference.
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*
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* ------------------------------------------------------------------------- */
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/file.h>
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#include <linux/pagemap.h>
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#include <linux/parser.h>
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#include <linux/bitops.h>
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#include <linux/smp_lock.h>
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#include "autofs_i.h"
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#include <linux/module.h>
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static void ino_lnkfree(struct autofs_info *ino)
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{
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kfree(ino->u.symlink);
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ino->u.symlink = NULL;
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}
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struct autofs_info *autofs4_init_ino(struct autofs_info *ino,
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struct autofs_sb_info *sbi, mode_t mode)
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{
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int reinit = 1;
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if (ino == NULL) {
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reinit = 0;
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ino = kmalloc(sizeof(*ino), GFP_KERNEL);
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}
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if (ino == NULL)
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return NULL;
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ino->flags = 0;
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ino->mode = mode;
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ino->inode = NULL;
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ino->dentry = NULL;
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ino->size = 0;
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ino->last_used = jiffies;
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ino->sbi = sbi;
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if (reinit && ino->free)
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(ino->free)(ino);
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memset(&ino->u, 0, sizeof(ino->u));
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ino->free = NULL;
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if (S_ISLNK(mode))
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ino->free = ino_lnkfree;
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return ino;
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}
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void autofs4_free_ino(struct autofs_info *ino)
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{
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if (ino->dentry) {
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ino->dentry->d_fsdata = NULL;
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if (ino->dentry->d_inode)
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dput(ino->dentry);
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ino->dentry = NULL;
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}
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if (ino->free)
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(ino->free)(ino);
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kfree(ino);
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}
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/*
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* Deal with the infamous "Busy inodes after umount ..." message.
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*
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* Clean up the dentry tree. This happens with autofs if the user
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* space program goes away due to a SIGKILL, SIGSEGV etc.
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*/
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static void autofs4_force_release(struct autofs_sb_info *sbi)
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{
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struct dentry *this_parent = sbi->root;
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struct list_head *next;
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spin_lock(&dcache_lock);
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repeat:
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next = this_parent->d_subdirs.next;
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resume:
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while (next != &this_parent->d_subdirs) {
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struct dentry *dentry = list_entry(next, struct dentry, d_u.d_child);
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/* Negative dentry - don`t care */
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if (!simple_positive(dentry)) {
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next = next->next;
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continue;
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}
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if (!list_empty(&dentry->d_subdirs)) {
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this_parent = dentry;
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goto repeat;
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}
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next = next->next;
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spin_unlock(&dcache_lock);
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DPRINTK("dentry %p %.*s",
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dentry, (int)dentry->d_name.len, dentry->d_name.name);
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dput(dentry);
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spin_lock(&dcache_lock);
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}
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if (this_parent != sbi->root) {
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struct dentry *dentry = this_parent;
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next = this_parent->d_u.d_child.next;
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this_parent = this_parent->d_parent;
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spin_unlock(&dcache_lock);
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DPRINTK("parent dentry %p %.*s",
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dentry, (int)dentry->d_name.len, dentry->d_name.name);
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dput(dentry);
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spin_lock(&dcache_lock);
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goto resume;
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}
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spin_unlock(&dcache_lock);
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dput(sbi->root);
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sbi->root = NULL;
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shrink_dcache_sb(sbi->sb);
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return;
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}
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static void autofs4_put_super(struct super_block *sb)
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{
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struct autofs_sb_info *sbi = autofs4_sbi(sb);
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sb->s_fs_info = NULL;
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if ( !sbi->catatonic )
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autofs4_catatonic_mode(sbi); /* Free wait queues, close pipe */
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/* Clean up and release dangling references */
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if (sbi)
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autofs4_force_release(sbi);
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kfree(sbi);
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DPRINTK("shutting down");
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}
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static struct super_operations autofs4_sops = {
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.put_super = autofs4_put_super,
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.statfs = simple_statfs,
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};
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enum {Opt_err, Opt_fd, Opt_uid, Opt_gid, Opt_pgrp, Opt_minproto, Opt_maxproto};
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static match_table_t tokens = {
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{Opt_fd, "fd=%u"},
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{Opt_uid, "uid=%u"},
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{Opt_gid, "gid=%u"},
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{Opt_pgrp, "pgrp=%u"},
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{Opt_minproto, "minproto=%u"},
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{Opt_maxproto, "maxproto=%u"},
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{Opt_err, NULL}
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};
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static int parse_options(char *options, int *pipefd, uid_t *uid, gid_t *gid,
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pid_t *pgrp, int *minproto, int *maxproto)
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{
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char *p;
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substring_t args[MAX_OPT_ARGS];
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int option;
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*uid = current->uid;
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*gid = current->gid;
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*pgrp = process_group(current);
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*minproto = AUTOFS_MIN_PROTO_VERSION;
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*maxproto = AUTOFS_MAX_PROTO_VERSION;
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*pipefd = -1;
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if (!options)
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return 1;
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while ((p = strsep(&options, ",")) != NULL) {
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int token;
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if (!*p)
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continue;
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token = match_token(p, tokens, args);
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switch (token) {
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case Opt_fd:
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if (match_int(args, pipefd))
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return 1;
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break;
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case Opt_uid:
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if (match_int(args, &option))
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return 1;
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*uid = option;
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break;
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case Opt_gid:
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if (match_int(args, &option))
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return 1;
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*gid = option;
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break;
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case Opt_pgrp:
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if (match_int(args, &option))
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return 1;
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*pgrp = option;
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break;
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case Opt_minproto:
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if (match_int(args, &option))
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return 1;
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*minproto = option;
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break;
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case Opt_maxproto:
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if (match_int(args, &option))
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return 1;
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*maxproto = option;
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break;
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default:
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return 1;
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}
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}
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return (*pipefd < 0);
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}
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static struct autofs_info *autofs4_mkroot(struct autofs_sb_info *sbi)
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{
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struct autofs_info *ino;
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ino = autofs4_init_ino(NULL, sbi, S_IFDIR | 0755);
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if (!ino)
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return NULL;
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return ino;
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}
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int autofs4_fill_super(struct super_block *s, void *data, int silent)
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{
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struct inode * root_inode;
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struct dentry * root;
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struct file * pipe;
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int pipefd;
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struct autofs_sb_info *sbi;
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struct autofs_info *ino;
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int minproto, maxproto;
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sbi = (struct autofs_sb_info *) kmalloc(sizeof(*sbi), GFP_KERNEL);
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if ( !sbi )
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goto fail_unlock;
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DPRINTK("starting up, sbi = %p",sbi);
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memset(sbi, 0, sizeof(*sbi));
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s->s_fs_info = sbi;
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sbi->magic = AUTOFS_SBI_MAGIC;
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sbi->root = NULL;
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sbi->catatonic = 0;
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sbi->exp_timeout = 0;
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sbi->oz_pgrp = process_group(current);
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sbi->sb = s;
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sbi->version = 0;
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sbi->sub_version = 0;
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init_MUTEX(&sbi->wq_sem);
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spin_lock_init(&sbi->fs_lock);
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sbi->queues = NULL;
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s->s_blocksize = 1024;
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s->s_blocksize_bits = 10;
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s->s_magic = AUTOFS_SUPER_MAGIC;
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s->s_op = &autofs4_sops;
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s->s_time_gran = 1;
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/*
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* Get the root inode and dentry, but defer checking for errors.
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*/
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ino = autofs4_mkroot(sbi);
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if (!ino)
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goto fail_free;
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root_inode = autofs4_get_inode(s, ino);
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kfree(ino);
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if (!root_inode)
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goto fail_free;
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root_inode->i_op = &autofs4_root_inode_operations;
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root_inode->i_fop = &autofs4_root_operations;
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root = d_alloc_root(root_inode);
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pipe = NULL;
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if (!root)
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goto fail_iput;
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/* Can this call block? */
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if (parse_options(data, &pipefd,
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&root_inode->i_uid, &root_inode->i_gid,
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&sbi->oz_pgrp,
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&minproto, &maxproto)) {
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printk("autofs: called with bogus options\n");
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goto fail_dput;
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}
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/* Couldn't this be tested earlier? */
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if (maxproto < AUTOFS_MIN_PROTO_VERSION ||
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minproto > AUTOFS_MAX_PROTO_VERSION) {
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printk("autofs: kernel does not match daemon version "
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"daemon (%d, %d) kernel (%d, %d)\n",
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minproto, maxproto,
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AUTOFS_MIN_PROTO_VERSION, AUTOFS_MAX_PROTO_VERSION);
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goto fail_dput;
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}
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sbi->version = maxproto > AUTOFS_MAX_PROTO_VERSION ? AUTOFS_MAX_PROTO_VERSION : maxproto;
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sbi->sub_version = AUTOFS_PROTO_SUBVERSION;
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DPRINTK("pipe fd = %d, pgrp = %u", pipefd, sbi->oz_pgrp);
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pipe = fget(pipefd);
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if ( !pipe ) {
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printk("autofs: could not open pipe file descriptor\n");
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goto fail_dput;
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}
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if ( !pipe->f_op || !pipe->f_op->write )
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goto fail_fput;
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sbi->pipe = pipe;
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/*
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* Take a reference to the root dentry so we get a chance to
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* clean up the dentry tree on umount.
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* See autofs4_force_release.
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*/
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sbi->root = dget(root);
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/*
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* Success! Install the root dentry now to indicate completion.
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*/
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s->s_root = root;
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return 0;
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/*
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* Failure ... clean up.
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*/
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fail_fput:
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printk("autofs: pipe file descriptor does not contain proper ops\n");
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fput(pipe);
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/* fall through */
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fail_dput:
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dput(root);
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goto fail_free;
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fail_iput:
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printk("autofs: get root dentry failed\n");
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iput(root_inode);
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fail_free:
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kfree(sbi);
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fail_unlock:
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return -EINVAL;
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}
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struct inode *autofs4_get_inode(struct super_block *sb,
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struct autofs_info *inf)
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{
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struct inode *inode = new_inode(sb);
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if (inode == NULL)
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return NULL;
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inf->inode = inode;
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inode->i_mode = inf->mode;
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if (sb->s_root) {
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inode->i_uid = sb->s_root->d_inode->i_uid;
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inode->i_gid = sb->s_root->d_inode->i_gid;
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} else {
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inode->i_uid = 0;
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inode->i_gid = 0;
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}
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inode->i_blksize = PAGE_CACHE_SIZE;
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inode->i_blocks = 0;
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inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
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if (S_ISDIR(inf->mode)) {
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inode->i_nlink = 2;
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inode->i_op = &autofs4_dir_inode_operations;
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inode->i_fop = &autofs4_dir_operations;
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} else if (S_ISLNK(inf->mode)) {
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inode->i_size = inf->size;
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inode->i_op = &autofs4_symlink_inode_operations;
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}
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return inode;
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}
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