[PATCH 8/17] [LogFS] inode.c

Joern Engel
2009-11-20T20:22:09Z

---
fs/logfs/inode.c | 417 +++++++

diff --git a/fs/logfs/inode.c b/fs/logfs/inode.c
new file mode 100644
index 0000000..6d08b37
--- /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);
+}