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![Dave Chinner](/assets/img/avatar_default.png)
Now that inode state changes are protected by the inode->i_lock and the inode LRU manipulations by the inode_lru_lock, we can remove the inode_lock from prune_icache and the initial part of iput_final(). instead of using the inode_lock to protect the inode during iput_final, use the inode->i_lock instead. This protects the inode against new references being taken while we change the inode state to I_FREEING, as well as preventing prune_icache from grabbing the inode while we are manipulating it. Hence we no longer need the inode_lock in iput_final prior to setting I_FREEING on the inode. For prune_icache, we no longer need the inode_lock to protect the LRU list, and the inodes themselves are protected against freeing races by the inode->i_lock. Hence we can lift the inode_lock from prune_icache as well. Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
405 lines
11 KiB
C
405 lines
11 KiB
C
/*
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* fs/logfs/inode.c - inode handling code
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*
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* As should be obvious for Linux kernel code, license is GPLv2
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*
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* Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
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*/
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#include "logfs.h"
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#include <linux/slab.h>
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#include <linux/writeback.h>
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#include <linux/backing-dev.h>
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/*
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* How soon to reuse old inode numbers? LogFS doesn't store deleted inodes
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* on the medium. It therefore also lacks a method to store the previous
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* generation number for deleted inodes. Instead a single generation number
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* is stored which will be used for new inodes. Being just a 32bit counter,
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* this can obvious wrap relatively quickly. So we only reuse inodes if we
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* know that a fair number of inodes can be created before we have to increment
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* the generation again - effectively adding some bits to the counter.
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* But being too aggressive here means we keep a very large and very sparse
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* inode file, wasting space on indirect blocks.
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* So what is a good value? Beats me. 64k seems moderately bad on both
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* fronts, so let's use that for now...
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*
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* NFS sucks, as everyone already knows.
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*/
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#define INOS_PER_WRAP (0x10000)
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/*
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* Logfs' requirement to read inodes for garbage collection makes life a bit
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* harder. GC may have to read inodes that are in I_FREEING state, when they
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* are being written out - and waiting for GC to make progress, naturally.
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*
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* So we cannot just call iget() or some variant of it, but first have to check
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* wether the inode in question might be in I_FREEING state. Therefore we
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* maintain our own per-sb list of "almost deleted" inodes and check against
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* that list first. Normally this should be at most 1-2 entries long.
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*
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* Also, inodes have logfs-specific reference counting on top of what the vfs
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* does. When .destroy_inode is called, normally the reference count will drop
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* to zero and the inode gets deleted. But if GC accessed the inode, its
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* refcount will remain nonzero and final deletion will have to wait.
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*
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* As a result we have two sets of functions to get/put inodes:
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* logfs_safe_iget/logfs_safe_iput - safe to call from GC context
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* logfs_iget/iput - normal version
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*/
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static struct kmem_cache *logfs_inode_cache;
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static DEFINE_SPINLOCK(logfs_inode_lock);
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static void logfs_inode_setops(struct inode *inode)
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{
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switch (inode->i_mode & S_IFMT) {
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case S_IFDIR:
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inode->i_op = &logfs_dir_iops;
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inode->i_fop = &logfs_dir_fops;
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inode->i_mapping->a_ops = &logfs_reg_aops;
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break;
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case S_IFREG:
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inode->i_op = &logfs_reg_iops;
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inode->i_fop = &logfs_reg_fops;
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inode->i_mapping->a_ops = &logfs_reg_aops;
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break;
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case S_IFLNK:
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inode->i_op = &logfs_symlink_iops;
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inode->i_mapping->a_ops = &logfs_reg_aops;
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break;
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case S_IFSOCK: /* fall through */
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case S_IFBLK: /* fall through */
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case S_IFCHR: /* fall through */
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case S_IFIFO:
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init_special_inode(inode, inode->i_mode, inode->i_rdev);
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break;
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default:
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BUG();
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}
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}
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static struct inode *__logfs_iget(struct super_block *sb, ino_t ino)
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{
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struct inode *inode = iget_locked(sb, ino);
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int err;
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if (!inode)
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return ERR_PTR(-ENOMEM);
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if (!(inode->i_state & I_NEW))
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return inode;
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err = logfs_read_inode(inode);
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if (err || inode->i_nlink == 0) {
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/* inode->i_nlink == 0 can be true when called from
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* block validator */
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/* set i_nlink to 0 to prevent caching */
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inode->i_nlink = 0;
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logfs_inode(inode)->li_flags |= LOGFS_IF_ZOMBIE;
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iget_failed(inode);
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if (!err)
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err = -ENOENT;
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return ERR_PTR(err);
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}
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logfs_inode_setops(inode);
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unlock_new_inode(inode);
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return inode;
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}
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struct inode *logfs_iget(struct super_block *sb, ino_t ino)
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{
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BUG_ON(ino == LOGFS_INO_MASTER);
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BUG_ON(ino == LOGFS_INO_SEGFILE);
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return __logfs_iget(sb, ino);
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}
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/*
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* is_cached is set to 1 if we hand out a cached inode, 0 otherwise.
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* this allows logfs_iput to do the right thing later
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*/
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struct inode *logfs_safe_iget(struct super_block *sb, ino_t ino, int *is_cached)
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{
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struct logfs_super *super = logfs_super(sb);
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struct logfs_inode *li;
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if (ino == LOGFS_INO_MASTER)
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return super->s_master_inode;
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if (ino == LOGFS_INO_SEGFILE)
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return super->s_segfile_inode;
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spin_lock(&logfs_inode_lock);
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list_for_each_entry(li, &super->s_freeing_list, li_freeing_list)
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if (li->vfs_inode.i_ino == ino) {
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li->li_refcount++;
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spin_unlock(&logfs_inode_lock);
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*is_cached = 1;
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return &li->vfs_inode;
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}
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spin_unlock(&logfs_inode_lock);
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*is_cached = 0;
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return __logfs_iget(sb, ino);
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}
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static void logfs_i_callback(struct rcu_head *head)
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{
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struct inode *inode = container_of(head, struct inode, i_rcu);
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INIT_LIST_HEAD(&inode->i_dentry);
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kmem_cache_free(logfs_inode_cache, logfs_inode(inode));
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}
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static void __logfs_destroy_inode(struct inode *inode)
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{
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struct logfs_inode *li = logfs_inode(inode);
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BUG_ON(li->li_block);
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list_del(&li->li_freeing_list);
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call_rcu(&inode->i_rcu, logfs_i_callback);
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}
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static void logfs_destroy_inode(struct inode *inode)
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{
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struct logfs_inode *li = logfs_inode(inode);
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BUG_ON(list_empty(&li->li_freeing_list));
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spin_lock(&logfs_inode_lock);
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li->li_refcount--;
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if (li->li_refcount == 0)
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__logfs_destroy_inode(inode);
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spin_unlock(&logfs_inode_lock);
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}
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void logfs_safe_iput(struct inode *inode, int is_cached)
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{
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if (inode->i_ino == LOGFS_INO_MASTER)
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return;
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if (inode->i_ino == LOGFS_INO_SEGFILE)
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return;
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if (is_cached) {
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logfs_destroy_inode(inode);
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return;
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}
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iput(inode);
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}
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static void logfs_init_inode(struct super_block *sb, struct inode *inode)
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{
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struct logfs_inode *li = logfs_inode(inode);
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int i;
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li->li_flags = 0;
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li->li_height = 0;
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li->li_used_bytes = 0;
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li->li_block = NULL;
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inode->i_uid = 0;
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inode->i_gid = 0;
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inode->i_size = 0;
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inode->i_blocks = 0;
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inode->i_ctime = CURRENT_TIME;
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inode->i_mtime = CURRENT_TIME;
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inode->i_nlink = 1;
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li->li_refcount = 1;
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INIT_LIST_HEAD(&li->li_freeing_list);
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for (i = 0; i < LOGFS_EMBEDDED_FIELDS; i++)
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li->li_data[i] = 0;
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return;
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}
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static struct inode *logfs_alloc_inode(struct super_block *sb)
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{
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struct logfs_inode *li;
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li = kmem_cache_alloc(logfs_inode_cache, GFP_NOFS);
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if (!li)
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return NULL;
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logfs_init_inode(sb, &li->vfs_inode);
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return &li->vfs_inode;
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}
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/*
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* In logfs inodes are written to an inode file. The inode file, like any
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* other file, is managed with a inode. The inode file's inode, aka master
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* inode, requires special handling in several respects. First, it cannot be
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* written to the inode file, so it is stored in the journal instead.
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*
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* Secondly, this inode cannot be written back and destroyed before all other
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* inodes have been written. The ordering is important. Linux' VFS is happily
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* unaware of the ordering constraint and would ordinarily destroy the master
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* inode at umount time while other inodes are still in use and dirty. Not
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* good.
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*
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* So logfs makes sure the master inode is not written until all other inodes
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* have been destroyed. Sadly, this method has another side-effect. The VFS
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* will notice one remaining inode and print a frightening warning message.
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* Worse, it is impossible to judge whether such a warning was caused by the
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* master inode or any other inodes have leaked as well.
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*
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* Our attempt of solving this is with logfs_new_meta_inode() below. Its
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* purpose is to create a new inode that will not trigger the warning if such
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* an inode is still in use. An ugly hack, no doubt. Suggections for
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* improvement are welcome.
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*
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* AV: that's what ->put_super() is for...
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*/
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struct inode *logfs_new_meta_inode(struct super_block *sb, u64 ino)
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{
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struct inode *inode;
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inode = new_inode(sb);
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if (!inode)
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return ERR_PTR(-ENOMEM);
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inode->i_mode = S_IFREG;
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inode->i_ino = ino;
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inode->i_data.a_ops = &logfs_reg_aops;
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mapping_set_gfp_mask(&inode->i_data, GFP_NOFS);
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return inode;
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}
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struct inode *logfs_read_meta_inode(struct super_block *sb, u64 ino)
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{
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struct inode *inode;
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int err;
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inode = logfs_new_meta_inode(sb, ino);
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if (IS_ERR(inode))
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return inode;
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err = logfs_read_inode(inode);
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if (err) {
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iput(inode);
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return ERR_PTR(err);
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}
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logfs_inode_setops(inode);
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return inode;
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}
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static int logfs_write_inode(struct inode *inode, struct writeback_control *wbc)
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{
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int ret;
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long flags = WF_LOCK;
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/* Can only happen if creat() failed. Safe to skip. */
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if (logfs_inode(inode)->li_flags & LOGFS_IF_STILLBORN)
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return 0;
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ret = __logfs_write_inode(inode, flags);
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LOGFS_BUG_ON(ret, inode->i_sb);
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return ret;
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}
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/* called with inode->i_lock held */
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static int logfs_drop_inode(struct inode *inode)
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{
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struct logfs_super *super = logfs_super(inode->i_sb);
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struct logfs_inode *li = logfs_inode(inode);
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spin_lock(&logfs_inode_lock);
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list_move(&li->li_freeing_list, &super->s_freeing_list);
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spin_unlock(&logfs_inode_lock);
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return generic_drop_inode(inode);
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}
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static void logfs_set_ino_generation(struct super_block *sb,
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struct inode *inode)
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{
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struct logfs_super *super = logfs_super(sb);
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u64 ino;
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mutex_lock(&super->s_journal_mutex);
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ino = logfs_seek_hole(super->s_master_inode, super->s_last_ino + 1);
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super->s_last_ino = ino;
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super->s_inos_till_wrap--;
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if (super->s_inos_till_wrap < 0) {
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super->s_last_ino = LOGFS_RESERVED_INOS;
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super->s_generation++;
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super->s_inos_till_wrap = INOS_PER_WRAP;
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}
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inode->i_ino = ino;
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inode->i_generation = super->s_generation;
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mutex_unlock(&super->s_journal_mutex);
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}
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struct inode *logfs_new_inode(struct inode *dir, int mode)
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{
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struct super_block *sb = dir->i_sb;
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struct inode *inode;
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inode = new_inode(sb);
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if (!inode)
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return ERR_PTR(-ENOMEM);
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logfs_init_inode(sb, inode);
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/* inherit parent flags */
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logfs_inode(inode)->li_flags |=
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logfs_inode(dir)->li_flags & LOGFS_FL_INHERITED;
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inode->i_mode = mode;
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logfs_set_ino_generation(sb, inode);
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inode_init_owner(inode, dir, mode);
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logfs_inode_setops(inode);
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insert_inode_hash(inode);
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return inode;
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}
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static void logfs_init_once(void *_li)
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{
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struct logfs_inode *li = _li;
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int i;
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li->li_flags = 0;
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li->li_used_bytes = 0;
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li->li_refcount = 1;
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for (i = 0; i < LOGFS_EMBEDDED_FIELDS; i++)
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li->li_data[i] = 0;
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inode_init_once(&li->vfs_inode);
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}
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static int logfs_sync_fs(struct super_block *sb, int wait)
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{
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logfs_write_anchor(sb);
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return 0;
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}
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static void logfs_put_super(struct super_block *sb)
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{
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struct logfs_super *super = logfs_super(sb);
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/* kill the meta-inodes */
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iput(super->s_master_inode);
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iput(super->s_segfile_inode);
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iput(super->s_mapping_inode);
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}
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const struct super_operations logfs_super_operations = {
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.alloc_inode = logfs_alloc_inode,
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.destroy_inode = logfs_destroy_inode,
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.evict_inode = logfs_evict_inode,
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.drop_inode = logfs_drop_inode,
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.put_super = logfs_put_super,
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.write_inode = logfs_write_inode,
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.statfs = logfs_statfs,
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.sync_fs = logfs_sync_fs,
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};
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int logfs_init_inode_cache(void)
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{
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logfs_inode_cache = kmem_cache_create("logfs_inode_cache",
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sizeof(struct logfs_inode), 0, SLAB_RECLAIM_ACCOUNT,
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logfs_init_once);
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if (!logfs_inode_cache)
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return -ENOMEM;
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return 0;
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}
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void logfs_destroy_inode_cache(void)
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{
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kmem_cache_destroy(logfs_inode_cache);
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}
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