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