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author | Joern Engel <joern@logfs.org> | 2009-11-20 20:13:39 +0100 |
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committer | Joern Engel <joern@logfs.org> | 2009-11-20 20:13:39 +0100 |
commit | 5db53f3e80dee2d9dff5e534f9e9fe1db17c9936 (patch) | |
tree | 066f2873eeb7eb86466f6389e45892d957db3de2 /fs/logfs/inode.c | |
parent | 66b00a7c93ec782d118d2c03bd599cfd041e80a1 (diff) | |
download | linux-5db53f3e80dee2d9dff5e534f9e9fe1db17c9936.tar.gz linux-5db53f3e80dee2d9dff5e534f9e9fe1db17c9936.tar.bz2 linux-5db53f3e80dee2d9dff5e534f9e9fe1db17c9936.zip |
[LogFS] add new flash file system
This is a new flash file system. See
Documentation/filesystems/logfs.txt
Signed-off-by: Joern Engel <joern@logfs.org>
Diffstat (limited to 'fs/logfs/inode.c')
-rw-r--r-- | fs/logfs/inode.c | 417 |
1 files changed, 417 insertions, 0 deletions
diff --git a/fs/logfs/inode.c b/fs/logfs/inode.c new file mode 100644 index 000000000000..6d08b3762641 --- /dev/null +++ b/fs/logfs/inode.c @@ -0,0 +1,417 @@ +/* + * 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/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 */ + inode->i_nlink = 0; + 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_destroy_inode(struct inode *inode) +{ + struct logfs_inode *li = logfs_inode(inode); + + BUG_ON(li->li_block); + list_del(&li->li_freeing_list); + kmem_cache_free(logfs_inode_cache, li); +} + +static void logfs_destroy_inode(struct inode *inode) +{ + struct logfs_inode *li = logfs_inode(inode); + + 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; + inode->i_nlink = 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. + */ +struct inode *logfs_new_meta_inode(struct super_block *sb, u64 ino) +{ + struct inode *inode; + + inode = logfs_alloc_inode(sb); + if (!inode) + return ERR_PTR(-ENOMEM); + + inode->i_mode = S_IFREG; + inode->i_ino = ino; + inode->i_sb = sb; + + /* This is a blatant copy of alloc_inode code. We'd need alloc_inode + * to be nonstatic, alas. */ + { + struct address_space * const mapping = &inode->i_data; + + mapping->a_ops = &logfs_reg_aops; + mapping->host = inode; + mapping->flags = 0; + mapping_set_gfp_mask(mapping, GFP_NOFS); + mapping->assoc_mapping = NULL; + mapping->backing_dev_info = &default_backing_dev_info; + inode->i_mapping = mapping; + inode->i_nlink = 1; + } + + 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) { + destroy_meta_inode(inode); + return ERR_PTR(err); + } + logfs_inode_setops(inode); + return inode; +} + +static int logfs_write_inode(struct inode *inode, int do_sync) +{ + 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, flags); + LOGFS_BUG_ON(ret, inode->i_sb); + return ret; +} + +void destroy_meta_inode(struct inode *inode) +{ + if (inode) { + if (inode->i_data.nrpages) + truncate_inode_pages(&inode->i_data, 0); + logfs_clear_inode(inode); + kmem_cache_free(logfs_inode_cache, logfs_inode(inode)); + } +} + +/* called with inode_lock held */ +static void 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); + 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); + 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, int 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->i_uid = current_fsuid(); + inode->i_gid = current_fsgid(); + if (dir->i_mode & S_ISGID) { + inode->i_gid = dir->i_gid; + if (S_ISDIR(mode)) + inode->i_mode |= S_ISGID; + } + + 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) +{ + /* FIXME: write anchor */ + logfs_super(sb)->s_devops->sync(sb); + return 0; +} + +const struct super_operations logfs_super_operations = { + .alloc_inode = logfs_alloc_inode, + .clear_inode = logfs_clear_inode, + .delete_inode = logfs_delete_inode, + .destroy_inode = logfs_destroy_inode, + .drop_inode = logfs_drop_inode, + .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); +} |