// SPDX-License-Identifier: GPL-2.0

  #include <linux/ceph/ceph_debug.h>

  
  #include <linux/spinlock.h>

  #include <linux/namei.h>

  #include <linux/slab.h>

  #include <linux/sched.h>

  #include <linux/xattr.h>

  
  #include "super.h"

  #include "mds_client.h"

  
  /*
   * Directory operations: readdir, lookup, create, link, unlink,
   * rename, etc.
   */
  
  /*
   * Ceph MDS operations are specified in terms of a base ino and
   * relative path.  Thus, the client can specify an operation on a
   * specific inode (e.g., a getattr due to fstat(2)), or as a path
   * relative to, say, the root directory.
   *
   * Normally, we limit ourselves to strict inode ops (no path component)
   * or dentry operations (a single path component relative to an ino).  The
   * exception to this is open_root_dentry(), which will open the mount
   * point by name.
   */

  const struct dentry_operations ceph_dentry_ops;

  static bool __dentry_lease_is_valid(struct ceph_dentry_info *di);
  static int __dir_lease_try_check(const struct dentry *dentry);

  /*
   * Initialize ceph dentry state.
   */

  static int ceph_d_init(struct dentry *dentry)

  {
  	struct ceph_dentry_info *di;

  	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(dentry->d_sb);

  	di = kmem_cache_zalloc(ceph_dentry_cachep, GFP_KERNEL);

  	if (!di)
  		return -ENOMEM;          /* oh well */

  	di->dentry = dentry;
  	di->lease_session = NULL;

  	di->time = jiffies;

  	dentry->d_fsdata = di;

  	INIT_LIST_HEAD(&di->lease_list);

  
  	atomic64_inc(&mdsc->metric.total_dentries);

  	return 0;
  }

  /*

   * for f_pos for readdir:
   * - hash order:
   *	(0xff << 52) | ((24 bits hash) << 28) |
   *	(the nth entry has hash collision);
   * - frag+name order;
   *	((frag value) << 28) | (the nth entry in frag);

   */

  #define OFFSET_BITS	28
  #define OFFSET_MASK	((1 << OFFSET_BITS) - 1)
  #define HASH_ORDER	(0xffull << (OFFSET_BITS + 24))
  loff_t ceph_make_fpos(unsigned high, unsigned off, bool hash_order)
  {
  	loff_t fpos = ((loff_t)high << 28) | (loff_t)off;
  	if (hash_order)
  		fpos |= HASH_ORDER;
  	return fpos;
  }
  
  static bool is_hash_order(loff_t p)
  {
  	return (p & HASH_ORDER) == HASH_ORDER;
  }

  static unsigned fpos_frag(loff_t p)
  {

  	return p >> OFFSET_BITS;

  }

  
  static unsigned fpos_hash(loff_t p)
  {
  	return ceph_frag_value(fpos_frag(p));
  }

  static unsigned fpos_off(loff_t p)
  {

  	return p & OFFSET_MASK;

  }

  static int fpos_cmp(loff_t l, loff_t r)
  {
  	int v = ceph_frag_compare(fpos_frag(l), fpos_frag(r));
  	if (v)
  		return v;
  	return (int)(fpos_off(l) - fpos_off(r));
  }

  /*

   * make note of the last dentry we read, so we can
   * continue at the same lexicographical point,
   * regardless of what dir changes take place on the
   * server.
   */

  static int note_last_dentry(struct ceph_dir_file_info *dfi, const char *name,

  		            int len, unsigned next_offset)
  {
  	char *buf = kmalloc(len+1, GFP_KERNEL);
  	if (!buf)
  		return -ENOMEM;

  	kfree(dfi->last_name);
  	dfi->last_name = buf;
  	memcpy(dfi->last_name, name, len);
  	dfi->last_name[len] = 0;
  	dfi->next_offset = next_offset;
  	dout("note_last_dentry '%s'
  ", dfi->last_name);

  	return 0;
  }

  
  static struct dentry *
  __dcache_find_get_entry(struct dentry *parent, u64 idx,
  			struct ceph_readdir_cache_control *cache_ctl)
  {
  	struct inode *dir = d_inode(parent);
  	struct dentry *dentry;
  	unsigned idx_mask = (PAGE_SIZE / sizeof(struct dentry *)) - 1;
  	loff_t ptr_pos = idx * sizeof(struct dentry *);
  	pgoff_t ptr_pgoff = ptr_pos >> PAGE_SHIFT;
  
  	if (ptr_pos >= i_size_read(dir))
  		return NULL;
  
  	if (!cache_ctl->page || ptr_pgoff != page_index(cache_ctl->page)) {
  		ceph_readdir_cache_release(cache_ctl);
  		cache_ctl->page = find_lock_page(&dir->i_data, ptr_pgoff);
  		if (!cache_ctl->page) {
  			dout(" page %lu not found
  ", ptr_pgoff);
  			return ERR_PTR(-EAGAIN);
  		}
  		/* reading/filling the cache are serialized by
  		   i_mutex, no need to use page lock */
  		unlock_page(cache_ctl->page);
  		cache_ctl->dentries = kmap(cache_ctl->page);
  	}
  
  	cache_ctl->index = idx & idx_mask;
  
  	rcu_read_lock();
  	spin_lock(&parent->d_lock);
  	/* check i_size again here, because empty directory can be
  	 * marked as complete while not holding the i_mutex. */
  	if (ceph_dir_is_complete_ordered(dir) && ptr_pos < i_size_read(dir))
  		dentry = cache_ctl->dentries[cache_ctl->index];
  	else
  		dentry = NULL;
  	spin_unlock(&parent->d_lock);
  	if (dentry && !lockref_get_not_dead(&dentry->d_lockref))
  		dentry = NULL;
  	rcu_read_unlock();
  	return dentry ? : ERR_PTR(-EAGAIN);
  }

  /*

   * When possible, we try to satisfy a readdir by peeking at the
   * dcache.  We make this work by carefully ordering dentries on

   * d_child when we initially get results back from the MDS, and

   * falling back to a "normal" sync readdir if any dentries in the dir
   * are dropped.
   *

   * Complete dir indicates that we have all dentries in the dir.  It is

   * defined IFF we hold CEPH_CAP_FILE_SHARED (which will be revoked by
   * the MDS if/when the directory is modified).
   */

  static int __dcache_readdir(struct file *file,  struct dir_context *ctx,

  			    int shared_gen)

  {

  	struct ceph_dir_file_info *dfi = file->private_data;

  	struct dentry *parent = file->f_path.dentry;

  	struct inode *dir = d_inode(parent);

  	struct dentry *dentry, *last = NULL;

  	struct ceph_dentry_info *di;

  	struct ceph_readdir_cache_control cache_ctl = {};

  	u64 idx = 0;
  	int err = 0;

  	dout("__dcache_readdir %p v%u at %llx
  ", dir, (unsigned)shared_gen, ctx->pos);

  	/* search start position */
  	if (ctx->pos > 2) {
  		u64 count = div_u64(i_size_read(dir), sizeof(struct dentry *));
  		while (count > 0) {
  			u64 step = count >> 1;
  			dentry = __dcache_find_get_entry(parent, idx + step,
  							 &cache_ctl);
  			if (!dentry) {
  				/* use linar search */
  				idx = 0;
  				break;
  			}
  			if (IS_ERR(dentry)) {
  				err = PTR_ERR(dentry);
  				goto out;
  			}
  			di = ceph_dentry(dentry);
  			spin_lock(&dentry->d_lock);
  			if (fpos_cmp(di->offset, ctx->pos) < 0) {
  				idx += step + 1;
  				count -= step + 1;
  			} else {
  				count = step;
  			}
  			spin_unlock(&dentry->d_lock);
  			dput(dentry);
  		}

  		dout("__dcache_readdir %p cache idx %llu
  ", dir, idx);

  	}

  	for (;;) {
  		bool emit_dentry = false;
  		dentry = __dcache_find_get_entry(parent, idx++, &cache_ctl);
  		if (!dentry) {

  			dfi->file_info.flags |= CEPH_F_ATEND;

  			err = 0;
  			break;

  		}

  		if (IS_ERR(dentry)) {
  			err = PTR_ERR(dentry);
  			goto out;

  		}

  		spin_lock(&dentry->d_lock);

  		di = ceph_dentry(dentry);
  		if (d_unhashed(dentry) ||
  		    d_really_is_negative(dentry) ||
  		    di->lease_shared_gen != shared_gen) {
  			spin_unlock(&dentry->d_lock);
  			dput(dentry);
  			err = -EAGAIN;
  			goto out;
  		}
  		if (fpos_cmp(ctx->pos, di->offset) <= 0) {

  			__ceph_dentry_dir_lease_touch(di);

  			emit_dentry = true;
  		}

  		spin_unlock(&dentry->d_lock);

  		if (emit_dentry) {

  			dout(" %llx dentry %p %pd %p
  ", di->offset,

  			     dentry, dentry, d_inode(dentry));
  			ctx->pos = di->offset;
  			if (!dir_emit(ctx, dentry->d_name.name,

  				      dentry->d_name.len, ceph_present_inode(d_inode(dentry)),

  				      d_inode(dentry)->i_mode >> 12)) {
  				dput(dentry);
  				err = 0;
  				break;
  			}
  			ctx->pos++;

  			if (last)
  				dput(last);
  			last = dentry;
  		} else {
  			dput(dentry);

  		}

  	}

  out:

  	ceph_readdir_cache_release(&cache_ctl);
  	if (last) {
  		int ret;
  		di = ceph_dentry(last);

  		ret = note_last_dentry(dfi, last->d_name.name, last->d_name.len,

  				       fpos_off(di->offset) + 1);
  		if (ret < 0)
  			err = ret;

  		dput(last);

  		/* last_name no longer match cache index */

  		if (dfi->readdir_cache_idx >= 0) {
  			dfi->readdir_cache_idx = -1;
  			dfi->dir_release_count = 0;

  		}

  	}

  	return err;
  }

  static bool need_send_readdir(struct ceph_dir_file_info *dfi, loff_t pos)

  {

  	if (!dfi->last_readdir)

  		return true;
  	if (is_hash_order(pos))

  		return !ceph_frag_contains_value(dfi->frag, fpos_hash(pos));

  	else

  		return dfi->frag != fpos_frag(pos);

  }

  static int ceph_readdir(struct file *file, struct dir_context *ctx)

  {

  	struct ceph_dir_file_info *dfi = file->private_data;

  	struct inode *inode = file_inode(file);

  	struct ceph_inode_info *ci = ceph_inode(inode);

  	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
  	struct ceph_mds_client *mdsc = fsc->mdsc;

  	int i;

  	int err;

  	unsigned frag = -1;

  	struct ceph_mds_reply_info_parsed *rinfo;

  	dout("readdir %p file %p pos %llx
  ", inode, file, ctx->pos);

  	if (dfi->file_info.flags & CEPH_F_ATEND)

  		return 0;
  
  	/* always start with . and .. */

  	if (ctx->pos == 0) {

  		dout("readdir off 0 -> '.'
  ");

  		if (!dir_emit(ctx, ".", 1, ceph_present_inode(inode),

  			    inode->i_mode >> 12))

  			return 0;

  		ctx->pos = 1;

  	}

  	if (ctx->pos == 1) {

  		u64 ino;
  		struct dentry *dentry = file->f_path.dentry;
  
  		spin_lock(&dentry->d_lock);
  		ino = ceph_present_inode(dentry->d_parent->d_inode);
  		spin_unlock(&dentry->d_lock);

  		dout("readdir off 1 -> '..'
  ");

  		if (!dir_emit(ctx, "..", 2, ino, inode->i_mode >> 12))

  			return 0;

  		ctx->pos = 2;

  	}

  	spin_lock(&ci->i_ceph_lock);

  	/* request Fx cap. if have Fx, we don't need to release Fs cap
  	 * for later create/unlink. */
  	__ceph_touch_fmode(ci, mdsc, CEPH_FILE_MODE_WR);
  	/* can we use the dcache? */

  	if (ceph_test_mount_opt(fsc, DCACHE) &&

  	    !ceph_test_mount_opt(fsc, NOASYNCREADDIR) &&

  	    ceph_snap(inode) != CEPH_SNAPDIR &&

  	    __ceph_dir_is_complete_ordered(ci) &&

  	    __ceph_caps_issued_mask_metric(ci, CEPH_CAP_FILE_SHARED, 1)) {

  		int shared_gen = atomic_read(&ci->i_shared_gen);

  		spin_unlock(&ci->i_ceph_lock);

  		err = __dcache_readdir(file, ctx, shared_gen);

  		if (err != -EAGAIN)

  			return err;

  	} else {

  		spin_unlock(&ci->i_ceph_lock);

  	}

  
  	/* proceed with a normal readdir */

  more:
  	/* do we have the correct frag content buffered? */

  	if (need_send_readdir(dfi, ctx->pos)) {

  		struct ceph_mds_request *req;
  		int op = ceph_snap(inode) == CEPH_SNAPDIR ?
  			CEPH_MDS_OP_LSSNAP : CEPH_MDS_OP_READDIR;
  
  		/* discard old result, if any */

  		if (dfi->last_readdir) {
  			ceph_mdsc_put_request(dfi->last_readdir);
  			dfi->last_readdir = NULL;

  		}

  		if (is_hash_order(ctx->pos)) {

  			/* fragtree isn't always accurate. choose frag
  			 * based on previous reply when possible. */
  			if (frag == (unsigned)-1)
  				frag = ceph_choose_frag(ci, fpos_hash(ctx->pos),
  							NULL, NULL);

  		} else {
  			frag = fpos_frag(ctx->pos);
  		}

  		dout("readdir fetching %llx.%llx frag %x offset '%s'
  ",

  		     ceph_vinop(inode), frag, dfi->last_name);

  		req = ceph_mdsc_create_request(mdsc, op, USE_AUTH_MDS);
  		if (IS_ERR(req))
  			return PTR_ERR(req);

  		err = ceph_alloc_readdir_reply_buffer(req, inode);
  		if (err) {
  			ceph_mdsc_put_request(req);
  			return err;
  		}

  		/* hints to request -> mds selection code */
  		req->r_direct_mode = USE_AUTH_MDS;

  		if (op == CEPH_MDS_OP_READDIR) {
  			req->r_direct_hash = ceph_frag_value(frag);
  			__set_bit(CEPH_MDS_R_DIRECT_IS_HASH, &req->r_req_flags);

  			req->r_inode_drop = CEPH_CAP_FILE_EXCL;

  		}

  		if (dfi->last_name) {
  			req->r_path2 = kstrdup(dfi->last_name, GFP_KERNEL);

  			if (!req->r_path2) {
  				ceph_mdsc_put_request(req);
  				return -ENOMEM;
  			}

  		} else if (is_hash_order(ctx->pos)) {
  			req->r_args.readdir.offset_hash =
  				cpu_to_le32(fpos_hash(ctx->pos));

  		}

  		req->r_dir_release_cnt = dfi->dir_release_count;
  		req->r_dir_ordered_cnt = dfi->dir_ordered_count;
  		req->r_readdir_cache_idx = dfi->readdir_cache_idx;
  		req->r_readdir_offset = dfi->next_offset;

  		req->r_args.readdir.frag = cpu_to_le32(frag);

  		req->r_args.readdir.flags =
  				cpu_to_le16(CEPH_READDIR_REPLY_BITFLAGS);

  
  		req->r_inode = inode;
  		ihold(inode);
  		req->r_dentry = dget(file->f_path.dentry);

  		err = ceph_mdsc_do_request(mdsc, NULL, req);
  		if (err < 0) {
  			ceph_mdsc_put_request(req);
  			return err;
  		}

  		dout("readdir got and parsed readdir result=%d on "
  		     "frag %x, end=%d, complete=%d, hash_order=%d
  ",
  		     err, frag,

  		     (int)req->r_reply_info.dir_end,

  		     (int)req->r_reply_info.dir_complete,
  		     (int)req->r_reply_info.hash_order);

  		rinfo = &req->r_reply_info;
  		if (le32_to_cpu(rinfo->dir_dir->frag) != frag) {
  			frag = le32_to_cpu(rinfo->dir_dir->frag);

  			if (!rinfo->hash_order) {

  				dfi->next_offset = req->r_readdir_offset;

  				/* adjust ctx->pos to beginning of frag */
  				ctx->pos = ceph_make_fpos(frag,

  							  dfi->next_offset,

  							  false);
  			}

  		}

  		dfi->frag = frag;
  		dfi->last_readdir = req;

  		if (test_bit(CEPH_MDS_R_DID_PREPOPULATE, &req->r_req_flags)) {

  			dfi->readdir_cache_idx = req->r_readdir_cache_idx;
  			if (dfi->readdir_cache_idx < 0) {

  				/* preclude from marking dir ordered */

  				dfi->dir_ordered_count = 0;

  			} else if (ceph_frag_is_leftmost(frag) &&

  				   dfi->next_offset == 2) {

  				/* note dir version at start of readdir so
  				 * we can tell if any dentries get dropped */

  				dfi->dir_release_count = req->r_dir_release_cnt;
  				dfi->dir_ordered_count = req->r_dir_ordered_cnt;

  			}
  		} else {

  			dout("readdir !did_prepopulate
  ");

  			/* disable readdir cache */

  			dfi->readdir_cache_idx = -1;

  			/* preclude from marking dir complete */

  			dfi->dir_release_count = 0;

  		}

  		/* note next offset and last dentry name */
  		if (rinfo->dir_nr > 0) {

  			struct ceph_mds_reply_dir_entry *rde =
  					rinfo->dir_entries + (rinfo->dir_nr-1);

  			unsigned next_offset = req->r_reply_info.dir_end ?
  					2 : (fpos_off(rde->offset) + 1);

  			err = note_last_dentry(dfi, rde->name, rde->name_len,

  					       next_offset);

  			if (err)
  				return err;

  		} else if (req->r_reply_info.dir_end) {

  			dfi->next_offset = 2;

  			/* keep last name */

  		}
  	}

  	rinfo = &dfi->last_readdir->r_reply_info;

  	dout("readdir frag %x num %d pos %llx chunk first %llx
  ",

  	     dfi->frag, rinfo->dir_nr, ctx->pos,

  	     rinfo->dir_nr ? rinfo->dir_entries[0].offset : 0LL);

  	i = 0;
  	/* search start position */
  	if (rinfo->dir_nr > 0) {
  		int step, nr = rinfo->dir_nr;
  		while (nr > 0) {
  			step = nr >> 1;
  			if (rinfo->dir_entries[i + step].offset < ctx->pos) {
  				i +=  step + 1;
  				nr -= step + 1;
  			} else {
  				nr = step;
  			}
  		}
  	}
  	for (; i < rinfo->dir_nr; i++) {
  		struct ceph_mds_reply_dir_entry *rde = rinfo->dir_entries + i;

  		BUG_ON(rde->offset < ctx->pos);
  
  		ctx->pos = rde->offset;
  		dout("readdir (%d/%d) -> %llx '%.*s' %p
  ",
  		     i, rinfo->dir_nr, ctx->pos,

  		     rde->name_len, rde->name, &rde->inode.in);

  		BUG_ON(!rde->inode.in);

  		if (!dir_emit(ctx, rde->name, rde->name_len,

  			      ceph_present_ino(inode->i_sb, le64_to_cpu(rde->inode.in->ino)),
  			      le32_to_cpu(rde->inode.in->mode) >> 12)) {

  			dout("filldir stopping us...
  ");
  			return 0;
  		}

  		ctx->pos++;

  	}

  	ceph_mdsc_put_request(dfi->last_readdir);
  	dfi->last_readdir = NULL;

  	if (dfi->next_offset > 2) {
  		frag = dfi->frag;

  		goto more;
  	}
  
  	/* more frags? */

  	if (!ceph_frag_is_rightmost(dfi->frag)) {
  		frag = ceph_frag_next(dfi->frag);

  		if (is_hash_order(ctx->pos)) {
  			loff_t new_pos = ceph_make_fpos(ceph_frag_value(frag),

  							dfi->next_offset, true);

  			if (new_pos > ctx->pos)
  				ctx->pos = new_pos;
  			/* keep last_name */
  		} else {

  			ctx->pos = ceph_make_fpos(frag, dfi->next_offset,
  							false);
  			kfree(dfi->last_name);
  			dfi->last_name = NULL;

  		}

  		dout("readdir next frag is %x
  ", frag);
  		goto more;
  	}

  	dfi->file_info.flags |= CEPH_F_ATEND;

  
  	/*
  	 * if dir_release_count still matches the dir, no dentries
  	 * were released during the whole readdir, and we should have
  	 * the complete dir contents in our cache.
  	 */

  	if (atomic64_read(&ci->i_release_count) ==
  					dfi->dir_release_count) {

  		spin_lock(&ci->i_ceph_lock);

  		if (dfi->dir_ordered_count ==
  				atomic64_read(&ci->i_ordered_count)) {

  			dout(" marking %p complete and ordered
  ", inode);

  			/* use i_size to track number of entries in
  			 * readdir cache */

  			BUG_ON(dfi->readdir_cache_idx < 0);
  			i_size_write(inode, dfi->readdir_cache_idx *

  				     sizeof(struct dentry*));
  		} else {

  			dout(" marking %p complete
  ", inode);

  		}

  		__ceph_dir_set_complete(ci, dfi->dir_release_count,
  					dfi->dir_ordered_count);

  		spin_unlock(&ci->i_ceph_lock);

  	}

  	dout("readdir %p file %p done.
  ", inode, file);

  	return 0;
  }

  static void reset_readdir(struct ceph_dir_file_info *dfi)

  {

  	if (dfi->last_readdir) {
  		ceph_mdsc_put_request(dfi->last_readdir);
  		dfi->last_readdir = NULL;

  	}

  	kfree(dfi->last_name);
  	dfi->last_name = NULL;
  	dfi->dir_release_count = 0;
  	dfi->readdir_cache_idx = -1;
  	dfi->next_offset = 2;  /* compensate for . and .. */
  	dfi->file_info.flags &= ~CEPH_F_ATEND;

  }

  /*
   * discard buffered readdir content on seekdir(0), or seek to new frag,
   * or seek prior to current chunk
   */

  static bool need_reset_readdir(struct ceph_dir_file_info *dfi, loff_t new_pos)

  {
  	struct ceph_mds_reply_info_parsed *rinfo;

  	loff_t chunk_offset;

  	if (new_pos == 0)
  		return true;

  	if (is_hash_order(new_pos)) {
  		/* no need to reset last_name for a forward seek when
  		 * dentries are sotred in hash order */

  	} else if (dfi->frag != fpos_frag(new_pos)) {

  		return true;

  	}

  	rinfo = dfi->last_readdir ? &dfi->last_readdir->r_reply_info : NULL;

  	if (!rinfo || !rinfo->dir_nr)
  		return true;

  	chunk_offset = rinfo->dir_entries[0].offset;
  	return new_pos < chunk_offset ||
  	       is_hash_order(new_pos) != is_hash_order(chunk_offset);

  }

  static loff_t ceph_dir_llseek(struct file *file, loff_t offset, int whence)

  {

  	struct ceph_dir_file_info *dfi = file->private_data;

  	struct inode *inode = file->f_mapping->host;

  	loff_t retval;

  	inode_lock(inode);

  	retval = -EINVAL;

  	switch (whence) {

  	case SEEK_CUR:
  		offset += file->f_pos;

  	case SEEK_SET:
  		break;

  	case SEEK_END:
  		retval = -EOPNOTSUPP;

  	default:
  		goto out;

  	}

  	if (offset >= 0) {

  		if (need_reset_readdir(dfi, offset)) {

  			dout("dir_llseek dropping %p content
  ", file);

  			reset_readdir(dfi);

  		} else if (is_hash_order(offset) && offset > file->f_pos) {
  			/* for hash offset, we don't know if a forward seek
  			 * is within same frag */

  			dfi->dir_release_count = 0;
  			dfi->readdir_cache_idx = -1;

  		}

  		if (offset != file->f_pos) {
  			file->f_pos = offset;
  			file->f_version = 0;

  			dfi->file_info.flags &= ~CEPH_F_ATEND;

  		}
  		retval = offset;

  	}

  out:

  	inode_unlock(inode);

  	return retval;
  }
  
  /*

   * Handle lookups for the hidden .snap directory.

   */

  int ceph_handle_snapdir(struct ceph_mds_request *req,
  			struct dentry *dentry, int err)

  {

  	struct ceph_fs_client *fsc = ceph_sb_to_client(dentry->d_sb);

  	struct inode *parent = d_inode(dentry->d_parent); /* we hold i_mutex */

  
  	/* .snap dir? */
  	if (err == -ENOENT &&

  	    ceph_snap(parent) == CEPH_NOSNAP &&

  	    strcmp(dentry->d_name.name,

  		   fsc->mount_options->snapdir_name) == 0) {

  		struct inode *inode = ceph_get_snapdir(parent);

  		dout("ENOENT on snapdir %p '%pd', linking to snapdir %p
  ",
  		     dentry, dentry, inode);

  		BUG_ON(!d_unhashed(dentry));

  		d_add(dentry, inode);
  		err = 0;
  	}

  	return err;
  }

  /*
   * Figure out final result of a lookup/open request.
   *
   * Mainly, make sure we return the final req->r_dentry (if it already
   * existed) in place of the original VFS-provided dentry when they
   * differ.
   *
   * Gracefully handle the case where the MDS replies with -ENOENT and
   * no trace (which it may do, at its discretion, e.g., if it doesn't
   * care to issue a lease on the negative dentry).
   */
  struct dentry *ceph_finish_lookup(struct ceph_mds_request *req,
  				  struct dentry *dentry, int err)
  {

  	if (err == -ENOENT) {
  		/* no trace? */
  		err = 0;
  		if (!req->r_reply_info.head->is_dentry) {
  			dout("ENOENT and no trace, dentry %p inode %p
  ",

  			     dentry, d_inode(dentry));
  			if (d_really_is_positive(dentry)) {

  				d_drop(dentry);
  				err = -ENOENT;
  			} else {
  				d_add(dentry, NULL);
  			}
  		}
  	}
  	if (err)
  		dentry = ERR_PTR(err);
  	else if (dentry != req->r_dentry)
  		dentry = dget(req->r_dentry);   /* we got spliced */
  	else
  		dentry = NULL;
  	return dentry;
  }

  static bool is_root_ceph_dentry(struct inode *inode, struct dentry *dentry)

  {
  	return ceph_ino(inode) == CEPH_INO_ROOT &&
  		strncmp(dentry->d_name.name, ".ceph", 5) == 0;
  }

  /*
   * Look up a single dir entry.  If there is a lookup intent, inform
   * the MDS so that it gets our 'caps wanted' value in a single op.
   */
  static struct dentry *ceph_lookup(struct inode *dir, struct dentry *dentry,

  				  unsigned int flags)

  {

  	struct ceph_fs_client *fsc = ceph_sb_to_client(dir->i_sb);

  	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(dir->i_sb);

  	struct ceph_mds_request *req;
  	int op;

  	int mask;

  	int err;

  	dout("lookup %p dentry %p '%pd'
  ",
  	     dir, dentry, dentry);

  
  	if (dentry->d_name.len > NAME_MAX)
  		return ERR_PTR(-ENAMETOOLONG);

  	/* can we conclude ENOENT locally? */

  	if (d_really_is_negative(dentry)) {

  		struct ceph_inode_info *ci = ceph_inode(dir);
  		struct ceph_dentry_info *di = ceph_dentry(dentry);

  		spin_lock(&ci->i_ceph_lock);

  		dout(" dir %p flags are 0x%lx
  ", dir, ci->i_ceph_flags);

  		if (strncmp(dentry->d_name.name,

  			    fsc->mount_options->snapdir_name,

  			    dentry->d_name.len) &&

  		    !is_root_ceph_dentry(dir, dentry) &&

  		    ceph_test_mount_opt(fsc, DCACHE) &&

  		    __ceph_dir_is_complete(ci) &&

  		    __ceph_caps_issued_mask_metric(ci, CEPH_CAP_FILE_SHARED, 1)) {

  			__ceph_touch_fmode(ci, mdsc, CEPH_FILE_MODE_RD);

  			spin_unlock(&ci->i_ceph_lock);

  			dout(" dir %p complete, -ENOENT
  ", dir);
  			d_add(dentry, NULL);

  			di->lease_shared_gen = atomic_read(&ci->i_shared_gen);

  			return NULL;
  		}

  		spin_unlock(&ci->i_ceph_lock);

  	}
  
  	op = ceph_snap(dir) == CEPH_SNAPDIR ?
  		CEPH_MDS_OP_LOOKUPSNAP : CEPH_MDS_OP_LOOKUP;
  	req = ceph_mdsc_create_request(mdsc, op, USE_ANY_MDS);
  	if (IS_ERR(req))

  		return ERR_CAST(req);

  	req->r_dentry = dget(dentry);
  	req->r_num_caps = 2;

  
  	mask = CEPH_STAT_CAP_INODE | CEPH_CAP_AUTH_SHARED;
  	if (ceph_security_xattr_wanted(dir))
  		mask |= CEPH_CAP_XATTR_SHARED;
  	req->r_args.getattr.mask = cpu_to_le32(mask);

  	req->r_parent = dir;
  	set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);

  	err = ceph_mdsc_do_request(mdsc, NULL, req);

  	err = ceph_handle_snapdir(req, dentry, err);

  	dentry = ceph_finish_lookup(req, dentry, err);
  	ceph_mdsc_put_request(req);  /* will dput(dentry) */
  	dout("lookup result=%p
  ", dentry);
  	return dentry;
  }
  
  /*
   * If we do a create but get no trace back from the MDS, follow up with
   * a lookup (the VFS expects us to link up the provided dentry).
   */
  int ceph_handle_notrace_create(struct inode *dir, struct dentry *dentry)
  {

  	struct dentry *result = ceph_lookup(dir, dentry, 0);

  
  	if (result && !IS_ERR(result)) {
  		/*
  		 * We created the item, then did a lookup, and found
  		 * it was already linked to another inode we already

  		 * had in our cache (and thus got spliced). To not
  		 * confuse VFS (especially when inode is a directory),
  		 * we don't link our dentry to that inode, return an
  		 * error instead.
  		 *
  		 * This event should be rare and it happens only when
  		 * we talk to old MDS. Recent MDS does not send traceless
  		 * reply for request that creates new inode.

  		 */

  		d_drop(result);

  		return -ESTALE;

  	}
  	return PTR_ERR(result);
  }
  
  static int ceph_mknod(struct inode *dir, struct dentry *dentry,

  		      umode_t mode, dev_t rdev)

  {

  	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(dir->i_sb);

  	struct ceph_mds_request *req;

  	struct ceph_acl_sec_ctx as_ctx = {};

  	int err;
  
  	if (ceph_snap(dir) != CEPH_NOSNAP)
  		return -EROFS;

  	if (ceph_quota_is_max_files_exceeded(dir)) {
  		err = -EDQUOT;
  		goto out;
  	}

  	err = ceph_pre_init_acls(dir, &mode, &as_ctx);

  	if (err < 0)

  		goto out;

  	err = ceph_security_init_secctx(dentry, mode, &as_ctx);
  	if (err < 0)
  		goto out;

  	dout("mknod in dir %p dentry %p mode 0%ho rdev %d
  ",

  	     dir, dentry, mode, rdev);
  	req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_MKNOD, USE_AUTH_MDS);
  	if (IS_ERR(req)) {

  		err = PTR_ERR(req);
  		goto out;

  	}
  	req->r_dentry = dget(dentry);
  	req->r_num_caps = 2;

  	req->r_parent = dir;
  	set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);

  	req->r_args.mknod.mode = cpu_to_le32(mode);
  	req->r_args.mknod.rdev = cpu_to_le32(rdev);

  	req->r_dentry_drop = CEPH_CAP_FILE_SHARED | CEPH_CAP_AUTH_EXCL;

  	req->r_dentry_unless = CEPH_CAP_FILE_EXCL;

  	if (as_ctx.pagelist) {
  		req->r_pagelist = as_ctx.pagelist;
  		as_ctx.pagelist = NULL;

  	}

  	err = ceph_mdsc_do_request(mdsc, dir, req);
  	if (!err && !req->r_reply_info.head->is_dentry)
  		err = ceph_handle_notrace_create(dir, dentry);
  	ceph_mdsc_put_request(req);

  out:

  	if (!err)

  		ceph_init_inode_acls(d_inode(dentry), &as_ctx);

  	else

  		d_drop(dentry);

  	ceph_release_acl_sec_ctx(&as_ctx);

  	return err;
  }

  static int ceph_create(struct inode *dir, struct dentry *dentry, umode_t mode,

  		       bool excl)

  {

  	return ceph_mknod(dir, dentry, mode, 0);

  }
  
  static int ceph_symlink(struct inode *dir, struct dentry *dentry,
  			    const char *dest)
  {

  	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(dir->i_sb);

  	struct ceph_mds_request *req;

  	struct ceph_acl_sec_ctx as_ctx = {};

  	int err;
  
  	if (ceph_snap(dir) != CEPH_NOSNAP)
  		return -EROFS;

  	if (ceph_quota_is_max_files_exceeded(dir)) {
  		err = -EDQUOT;
  		goto out;
  	}

  	err = ceph_security_init_secctx(dentry, S_IFLNK | 0777, &as_ctx);
  	if (err < 0)
  		goto out;

  	dout("symlink in dir %p dentry %p to '%s'
  ", dir, dentry, dest);
  	req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_SYMLINK, USE_AUTH_MDS);
  	if (IS_ERR(req)) {

  		err = PTR_ERR(req);
  		goto out;

  	}

  	req->r_path2 = kstrdup(dest, GFP_KERNEL);

  	if (!req->r_path2) {
  		err = -ENOMEM;
  		ceph_mdsc_put_request(req);
  		goto out;
  	}

  	req->r_parent = dir;
  	set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);

  	req->r_dentry = dget(dentry);
  	req->r_num_caps = 2;

  	req->r_dentry_drop = CEPH_CAP_FILE_SHARED | CEPH_CAP_AUTH_EXCL;

  	req->r_dentry_unless = CEPH_CAP_FILE_EXCL;

  	if (as_ctx.pagelist) {
  		req->r_pagelist = as_ctx.pagelist;
  		as_ctx.pagelist = NULL;
  	}

  	err = ceph_mdsc_do_request(mdsc, dir, req);
  	if (!err && !req->r_reply_info.head->is_dentry)
  		err = ceph_handle_notrace_create(dir, dentry);
  	ceph_mdsc_put_request(req);

  out:
  	if (err)

  		d_drop(dentry);

  	ceph_release_acl_sec_ctx(&as_ctx);

  	return err;
  }

  static int ceph_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)

  {

  	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(dir->i_sb);

  	struct ceph_mds_request *req;

  	struct ceph_acl_sec_ctx as_ctx = {};

  	int err = -EROFS;
  	int op;
  
  	if (ceph_snap(dir) == CEPH_SNAPDIR) {
  		/* mkdir .snap/foo is a MKSNAP */
  		op = CEPH_MDS_OP_MKSNAP;

  		dout("mksnap dir %p snap '%pd' dn %p
  ", dir,
  		     dentry, dentry);

  	} else if (ceph_snap(dir) == CEPH_NOSNAP) {

  		dout("mkdir dir %p dn %p mode 0%ho
  ", dir, dentry, mode);

  		op = CEPH_MDS_OP_MKDIR;
  	} else {
  		goto out;
  	}

  	if (op == CEPH_MDS_OP_MKDIR &&
  	    ceph_quota_is_max_files_exceeded(dir)) {

  		err = -EDQUOT;
  		goto out;
  	}

  	mode |= S_IFDIR;

  	err = ceph_pre_init_acls(dir, &mode, &as_ctx);

  	if (err < 0)
  		goto out;

  	err = ceph_security_init_secctx(dentry, mode, &as_ctx);
  	if (err < 0)
  		goto out;

  	req = ceph_mdsc_create_request(mdsc, op, USE_AUTH_MDS);
  	if (IS_ERR(req)) {
  		err = PTR_ERR(req);
  		goto out;
  	}
  
  	req->r_dentry = dget(dentry);
  	req->r_num_caps = 2;

  	req->r_parent = dir;
  	set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);

  	req->r_args.mkdir.mode = cpu_to_le32(mode);

  	req->r_dentry_drop = CEPH_CAP_FILE_SHARED | CEPH_CAP_AUTH_EXCL;

  	req->r_dentry_unless = CEPH_CAP_FILE_EXCL;

  	if (as_ctx.pagelist) {
  		req->r_pagelist = as_ctx.pagelist;
  		as_ctx.pagelist = NULL;

  	}

  	err = ceph_mdsc_do_request(mdsc, dir, req);

  	if (!err &&
  	    !req->r_reply_info.head->is_target &&
  	    !req->r_reply_info.head->is_dentry)

  		err = ceph_handle_notrace_create(dir, dentry);
  	ceph_mdsc_put_request(req);
  out:

  	if (!err)

  		ceph_init_inode_acls(d_inode(dentry), &as_ctx);

  	else

  		d_drop(dentry);

  	ceph_release_acl_sec_ctx(&as_ctx);

  	return err;
  }
  
  static int ceph_link(struct dentry *old_dentry, struct inode *dir,
  		     struct dentry *dentry)
  {

  	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(dir->i_sb);

  	struct ceph_mds_request *req;
  	int err;
  
  	if (ceph_snap(dir) != CEPH_NOSNAP)
  		return -EROFS;
  
  	dout("link in dir %p old_dentry %p dentry %p
  ", dir,
  	     old_dentry, dentry);
  	req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_LINK, USE_AUTH_MDS);
  	if (IS_ERR(req)) {
  		d_drop(dentry);
  		return PTR_ERR(req);
  	}
  	req->r_dentry = dget(dentry);
  	req->r_num_caps = 2;

  	req->r_old_dentry = dget(old_dentry);

  	req->r_parent = dir;
  	set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);

  	req->r_dentry_drop = CEPH_CAP_FILE_SHARED;
  	req->r_dentry_unless = CEPH_CAP_FILE_EXCL;

  	/* release LINK_SHARED on source inode (mds will lock it) */

  	req->r_old_inode_drop = CEPH_CAP_LINK_SHARED | CEPH_CAP_LINK_EXCL;

  	err = ceph_mdsc_do_request(mdsc, dir, req);

  	if (err) {

  		d_drop(dentry);

  	} else if (!req->r_reply_info.head->is_dentry) {

  		ihold(d_inode(old_dentry));
  		d_instantiate(dentry, d_inode(old_dentry));

  	}

  	ceph_mdsc_put_request(req);
  	return err;
  }

  static void ceph_async_unlink_cb(struct ceph_mds_client *mdsc,
  				 struct ceph_mds_request *req)
  {
  	int result = req->r_err ? req->r_err :
  			le32_to_cpu(req->r_reply_info.head->result);
  
  	if (result == -EJUKEBOX)
  		goto out;
  
  	/* If op failed, mark everyone involved for errors */
  	if (result) {

  		int pathlen = 0;
  		u64 base = 0;

  		char *path = ceph_mdsc_build_path(req->r_dentry, &pathlen,
  						  &base, 0);
  
  		/* mark error on parent + clear complete */
  		mapping_set_error(req->r_parent->i_mapping, result);
  		ceph_dir_clear_complete(req->r_parent);
  
  		/* drop the dentry -- we don't know its status */
  		if (!d_unhashed(req->r_dentry))
  			d_drop(req->r_dentry);
  
  		/* mark inode itself for an error (since metadata is bogus) */
  		mapping_set_error(req->r_old_inode->i_mapping, result);
  
  		pr_warn("ceph: async unlink failure path=(%llx)%s result=%d!
  ",
  			base, IS_ERR(path) ? "<<bad>>" : path, result);
  		ceph_mdsc_free_path(path, pathlen);
  	}
  out:
  	iput(req->r_old_inode);
  	ceph_mdsc_release_dir_caps(req);
  }
  
  static int get_caps_for_async_unlink(struct inode *dir, struct dentry *dentry)
  {
  	struct ceph_inode_info *ci = ceph_inode(dir);
  	struct ceph_dentry_info *di;
  	int got = 0, want = CEPH_CAP_FILE_EXCL | CEPH_CAP_DIR_UNLINK;
  
  	spin_lock(&ci->i_ceph_lock);
  	if ((__ceph_caps_issued(ci, NULL) & want) == want) {
  		ceph_take_cap_refs(ci, want, false);
  		got = want;
  	}
  	spin_unlock(&ci->i_ceph_lock);
  
  	/* If we didn't get anything, return 0 */
  	if (!got)
  		return 0;
  
          spin_lock(&dentry->d_lock);
          di = ceph_dentry(dentry);
  	/*
  	 * - We are holding Fx, which implies Fs caps.
  	 * - Only support async unlink for primary linkage
  	 */
  	if (atomic_read(&ci->i_shared_gen) != di->lease_shared_gen ||
  	    !(di->flags & CEPH_DENTRY_PRIMARY_LINK))
  		want = 0;
          spin_unlock(&dentry->d_lock);
  
  	/* Do we still want what we've got? */
  	if (want == got)
  		return got;
  
  	ceph_put_cap_refs(ci, got);
  	return 0;
  }

  /*

   * rmdir and unlink are differ only by the metadata op code
   */
  static int ceph_unlink(struct inode *dir, struct dentry *dentry)
  {

  	struct ceph_fs_client *fsc = ceph_sb_to_client(dir->i_sb);
  	struct ceph_mds_client *mdsc = fsc->mdsc;

  	struct inode *inode = d_inode(dentry);

  	struct ceph_mds_request *req;

  	bool try_async = ceph_test_mount_opt(fsc, ASYNC_DIROPS);

  	int err = -EROFS;
  	int op;
  
  	if (ceph_snap(dir) == CEPH_SNAPDIR) {
  		/* rmdir .snap/foo is RMSNAP */

  		dout("rmsnap dir %p '%pd' dn %p
  ", dir, dentry, dentry);

  		op = CEPH_MDS_OP_RMSNAP;
  	} else if (ceph_snap(dir) == CEPH_NOSNAP) {
  		dout("unlink/rmdir dir %p dn %p inode %p
  ",
  		     dir, dentry, inode);

  		op = d_is_dir(dentry) ?

  			CEPH_MDS_OP_RMDIR : CEPH_MDS_OP_UNLINK;
  	} else
  		goto out;

  retry:

  	req = ceph_mdsc_create_request(mdsc, op, USE_AUTH_MDS);
  	if (IS_ERR(req)) {
  		err = PTR_ERR(req);
  		goto out;
  	}
  	req->r_dentry = dget(dentry);
  	req->r_num_caps = 2;

  	req->r_parent = dir;

  	req->r_dentry_drop = CEPH_CAP_FILE_SHARED;
  	req->r_dentry_unless = CEPH_CAP_FILE_EXCL;

  	req->r_inode_drop = ceph_drop_caps_for_unlink(inode);

  
  	if (try_async && op == CEPH_MDS_OP_UNLINK &&
  	    (req->r_dir_caps = get_caps_for_async_unlink(dir, dentry))) {

  		dout("async unlink on %llu/%.*s caps=%s", ceph_ino(dir),

  		     dentry->d_name.len, dentry->d_name.name,
  		     ceph_cap_string(req->r_dir_caps));
  		set_bit(CEPH_MDS_R_ASYNC, &req->r_req_flags);
  		req->r_callback = ceph_async_unlink_cb;
  		req->r_old_inode = d_inode(dentry);
  		ihold(req->r_old_inode);
  		err = ceph_mdsc_submit_request(mdsc, dir, req);
  		if (!err) {
  			/*
  			 * We have enough caps, so we assume that the unlink
  			 * will succeed. Fix up the target inode and dcache.
  			 */
  			drop_nlink(inode);
  			d_delete(dentry);
  		} else if (err == -EJUKEBOX) {
  			try_async = false;
  			ceph_mdsc_put_request(req);
  			goto retry;
  		}
  	} else {
  		set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
  		err = ceph_mdsc_do_request(mdsc, dir, req);
  		if (!err && !req->r_reply_info.head->is_dentry)
  			d_delete(dentry);
  	}

  	ceph_mdsc_put_request(req);
  out:
  	return err;
  }
  
  static int ceph_rename(struct inode *old_dir, struct dentry *old_dentry,

  		       struct inode *new_dir, struct dentry *new_dentry,
  		       unsigned int flags)

  {

  	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(old_dir->i_sb);

  	struct ceph_mds_request *req;

  	int op = CEPH_MDS_OP_RENAME;

  	int err;

  	if (flags)
  		return -EINVAL;

  	if (ceph_snap(old_dir) != ceph_snap(new_dir))
  		return -EXDEV;

  	if (ceph_snap(old_dir) != CEPH_NOSNAP) {
  		if (old_dir == new_dir && ceph_snap(old_dir) == CEPH_SNAPDIR)
  			op = CEPH_MDS_OP_RENAMESNAP;
  		else
  			return -EROFS;

  	} else if (old_dir != new_dir) {
  		err = ceph_quota_check_rename(mdsc, d_inode(old_dentry),
  					      new_dir);
  		if (err)
  			return err;

  	}

  	dout("rename dir %p dentry %p to dir %p dentry %p
  ",
  	     old_dir, old_dentry, new_dir, new_dentry);

  	req = ceph_mdsc_create_request(mdsc, op, USE_AUTH_MDS);

  	if (IS_ERR(req))
  		return PTR_ERR(req);

  	ihold(old_dir);

  	req->r_dentry = dget(new_dentry);
  	req->r_num_caps = 2;
  	req->r_old_dentry = dget(old_dentry);

  	req->r_old_dentry_dir = old_dir;

  	req->r_parent = new_dir;
  	set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);

  	req->r_old_dentry_drop = CEPH_CAP_FILE_SHARED;
  	req->r_old_dentry_unless = CEPH_CAP_FILE_EXCL;
  	req->r_dentry_drop = CEPH_CAP_FILE_SHARED;
  	req->r_dentry_unless = CEPH_CAP_FILE_EXCL;
  	/* release LINK_RDCACHE on source inode (mds will lock it) */

  	req->r_old_inode_drop = CEPH_CAP_LINK_SHARED | CEPH_CAP_LINK_EXCL;

  	if (d_really_is_positive(new_dentry)) {
  		req->r_inode_drop =
  			ceph_drop_caps_for_unlink(d_inode(new_dentry));
  	}

  	err = ceph_mdsc_do_request(mdsc, old_dir, req);
  	if (!err && !req->r_reply_info.head->is_dentry) {
  		/*
  		 * Normally d_move() is done by fill_trace (called by
  		 * do_request, above).  If there is no trace, we need
  		 * to do it here.
  		 */
  		d_move(old_dentry, new_dentry);
  	}
  	ceph_mdsc_put_request(req);
  	return err;
  }

  /*

   * Move dentry to tail of mdsc->dentry_leases list when lease is updated.
   * Leases at front of the list will expire first. (Assume all leases have
   * similar duration)
   *
   * Called under dentry->d_lock.
   */
  void __ceph_dentry_lease_touch(struct ceph_dentry_info *di)
  {
  	struct dentry *dn = di->dentry;
  	struct ceph_mds_client *mdsc;
  
  	dout("dentry_lease_touch %p %p '%pd'
  ", di, dn, dn);
  
  	di->flags |= CEPH_DENTRY_LEASE_LIST;
  	if (di->flags & CEPH_DENTRY_SHRINK_LIST) {
  		di->flags |= CEPH_DENTRY_REFERENCED;
  		return;
  	}
  
  	mdsc = ceph_sb_to_client(dn->d_sb)->mdsc;
  	spin_lock(&mdsc->dentry_list_lock);
  	list_move_tail(&di->lease_list, &mdsc->dentry_leases);
  	spin_unlock(&mdsc->dentry_list_lock);
  }
  
  static void __dentry_dir_lease_touch(struct ceph_mds_client* mdsc,
  				     struct ceph_dentry_info *di)
  {
  	di->flags &= ~(CEPH_DENTRY_LEASE_LIST | CEPH_DENTRY_REFERENCED);
  	di->lease_gen = 0;
  	di->time = jiffies;
  	list_move_tail(&di->lease_list, &mdsc->dentry_dir_leases);
  }
  
  /*
   * When dir lease is used, add dentry to tail of mdsc->dentry_dir_leases
   * list if it's not in the list, otherwise set 'referenced' flag.
   *
   * Called under dentry->d_lock.
   */
  void __ceph_dentry_dir_lease_touch(struct ceph_dentry_info *di)
  {
  	struct dentry *dn = di->dentry;
  	struct ceph_mds_client *mdsc;

  	dout("dentry_dir_lease_touch %p %p '%pd' (offset 0x%llx)
  ",

  	     di, dn, dn, di->offset);
  
  	if (!list_empty(&di->lease_list)) {
  		if (di->flags & CEPH_DENTRY_LEASE_LIST) {
  			/* don't remove dentry from dentry lease list
  			 * if its lease is valid */
  			if (__dentry_lease_is_valid(di))
  				return;
  		} else {
  			di->flags |= CEPH_DENTRY_REFERENCED;
  			return;
  		}
  	}
  
  	if (di->flags & CEPH_DENTRY_SHRINK_LIST) {
  		di->flags |= CEPH_DENTRY_REFERENCED;
  		di->flags &= ~CEPH_DENTRY_LEASE_LIST;
  		return;
  	}
  
  	mdsc = ceph_sb_to_client(dn->d_sb)->mdsc;
  	spin_lock(&mdsc->dentry_list_lock);
  	__dentry_dir_lease_touch(mdsc, di),
  	spin_unlock(&mdsc->dentry_list_lock);
  }
  
  static void __dentry_lease_unlist(struct ceph_dentry_info *di)
  {
  	struct ceph_mds_client *mdsc;
  	if (di->flags & CEPH_DENTRY_SHRINK_LIST)
  		return;
  	if (list_empty(&di->lease_list))
  		return;
  
  	mdsc = ceph_sb_to_client(di->dentry->d_sb)->mdsc;
  	spin_lock(&mdsc->dentry_list_lock);
  	list_del_init(&di->lease_list);
  	spin_unlock(&mdsc->dentry_list_lock);
  }
  
  enum {
  	KEEP	= 0,
  	DELETE	= 1,
  	TOUCH	= 2,
  	STOP	= 4,
  };
  
  struct ceph_lease_walk_control {
  	bool dir_lease;

  	bool expire_dir_lease;

  	unsigned long nr_to_scan;
  	unsigned long dir_lease_ttl;
  };
  
  static unsigned long
  __dentry_leases_walk(struct ceph_mds_client *mdsc,
  		     struct ceph_lease_walk_control *lwc,
  		     int (*check)(struct dentry*, void*))
  {
  	struct ceph_dentry_info *di, *tmp;
  	struct dentry *dentry, *last = NULL;
  	struct list_head* list;
          LIST_HEAD(dispose);
  	unsigned long freed = 0;
  	int ret = 0;
  
  	list = lwc->dir_lease ? &mdsc->dentry_dir_leases : &mdsc->dentry_leases;
  	spin_lock(&mdsc->dentry_list_lock);
  	list_for_each_entry_safe(di, tmp, list, lease_list) {
  		if (!lwc->nr_to_scan)
  			break;
  		--lwc->nr_to_scan;
  
  		dentry = di->dentry;
  		if (last == dentry)
  			break;
  
  		if (!spin_trylock(&dentry->d_lock))
  			continue;

  		if (__lockref_is_dead(&dentry->d_lockref)) {

  			list_del_init(&di->lease_list);
  			goto next;
  		}
  
  		ret = check(dentry, lwc);
  		if (ret & TOUCH) {
  			/* move it into tail of dir lease list */
  			__dentry_dir_lease_touch(mdsc, di);
  			if (!last)
  				last = dentry;
  		}
  		if (ret & DELETE) {
  			/* stale lease */
  			di->flags &= ~CEPH_DENTRY_REFERENCED;
  			if (dentry->d_lockref.count > 0) {
  				/* update_dentry_lease() will re-add
  				 * it to lease list, or
  				 * ceph_d_delete() will return 1 when
  				 * last reference is dropped */
  				list_del_init(&di->lease_list);
  			} else {
  				di->flags |= CEPH_DENTRY_SHRINK_LIST;
  				list_move_tail(&di->lease_list, &dispose);
  				dget_dlock(dentry);
  			}
  		}
  next:
  		spin_unlock(&dentry->d_lock);
  		if (ret & STOP)
  			break;
  	}
  	spin_unlock(&mdsc->dentry_list_lock);
  
  	while (!list_empty(&dispose)) {
  		di = list_first_entry(&dispose, struct ceph_dentry_info,
  				      lease_list);
  		dentry = di->dentry;
  		spin_lock(&dentry->d_lock);
  
  		list_del_init(&di->lease_list);
  		di->flags &= ~CEPH_DENTRY_SHRINK_LIST;
  		if (di->flags & CEPH_DENTRY_REFERENCED) {
  			spin_lock(&mdsc->dentry_list_lock);
  			if (di->flags & CEPH_DENTRY_LEASE_LIST) {
  				list_add_tail(&di->lease_list,
  					      &mdsc->dentry_leases);
  			} else {
  				__dentry_dir_lease_touch(mdsc, di);
  			}
  			spin_unlock(&mdsc->dentry_list_lock);
  		} else {
  			freed++;
  		}
  
  		spin_unlock(&dentry->d_lock);
  		/* ceph_d_delete() does the trick */
  		dput(dentry);
  	}
  	return freed;
  }
  
  static int __dentry_lease_check(struct dentry *dentry, void *arg)
  {
  	struct ceph_dentry_info *di = ceph_dentry(dentry);
  	int ret;
  
  	if (__dentry_lease_is_valid(di))
  		return STOP;
  	ret = __dir_lease_try_check(dentry);
  	if (ret == -EBUSY)
  		return KEEP;
  	if (ret > 0)
  		return TOUCH;
  	return DELETE;
  }
  
  static int __dir_lease_check(struct dentry *dentry, void *arg)
  {
  	struct ceph_lease_walk_control *lwc = arg;
  	struct ceph_dentry_info *di = ceph_dentry(dentry);
  
  	int ret = __dir_lease_try_check(dentry);
  	if (ret == -EBUSY)
  		return KEEP;
  	if (ret > 0) {
  		if (time_before(jiffies, di->time + lwc->dir_lease_ttl))
  			return STOP;
  		/* Move dentry to tail of dir lease list if we don't want
  		 * to delete it. So dentries in the list are checked in a
  		 * round robin manner */

  		if (!lwc->expire_dir_lease)
  			return TOUCH;
  		if (dentry->d_lockref.count > 0 ||
  		    (di->flags & CEPH_DENTRY_REFERENCED))
  			return TOUCH;
  		/* invalidate dir lease */
  		di->lease_shared_gen = 0;

  	}
  	return DELETE;
  }
  
  int ceph_trim_dentries(struct ceph_mds_client *mdsc)
  {
  	struct ceph_lease_walk_control lwc;

  	unsigned long count;

  	unsigned long freed;

  	spin_lock(&mdsc->caps_list_lock);
          if (mdsc->caps_use_max > 0 &&
              mdsc->caps_use_count > mdsc->caps_use_max)
  		count = mdsc->caps_use_count - mdsc->caps_use_max;
  	else
  		count = 0;
          spin_unlock(&mdsc->caps_list_lock);

  	lwc.dir_lease = false;
  	lwc.nr_to_scan  = CEPH_CAPS_PER_RELEASE * 2;
  	freed = __dentry_leases_walk(mdsc, &lwc, __dentry_lease_check);
  	if (!lwc.nr_to_scan) /* more invalid leases */
  		return -EAGAIN;
  
  	if (lwc.nr_to_scan < CEPH_CAPS_PER_RELEASE)
  		lwc.nr_to_scan = CEPH_CAPS_PER_RELEASE;
  
  	lwc.dir_lease = true;

  	lwc.expire_dir_lease = freed < count;
  	lwc.dir_lease_ttl = mdsc->fsc->mount_options->caps_wanted_delay_max * HZ;

  	freed +=__dentry_leases_walk(mdsc, &lwc, __dir_lease_check);
  	if (!lwc.nr_to_scan) /* more to check */
  		return -EAGAIN;
  
  	return freed > 0 ? 1 : 0;
  }
  
  /*

   * Ensure a dentry lease will no longer revalidate.
   */
  void ceph_invalidate_dentry_lease(struct dentry *dentry)
  {

  	struct ceph_dentry_info *di = ceph_dentry(dentry);

  	spin_lock(&dentry->d_lock);

  	di->time = jiffies;
  	di->lease_shared_gen = 0;

  	di->flags &= ~CEPH_DENTRY_PRIMARY_LINK;

  	__dentry_lease_unlist(di);

  	spin_unlock(&dentry->d_lock);
  }

  
  /*
   * Check if dentry lease is valid.  If not, delete the lease.  Try to
   * renew if the least is more than half up.
   */

  static bool __dentry_lease_is_valid(struct ceph_dentry_info *di)
  {
  	struct ceph_mds_session *session;
  
  	if (!di->lease_gen)
  		return false;
  
  	session = di->lease_session;
  	if (session) {
  		u32 gen;
  		unsigned long ttl;
  
  		spin_lock(&session->s_gen_ttl_lock);
  		gen = session->s_cap_gen;
  		ttl = session->s_cap_ttl;
  		spin_unlock(&session->s_gen_ttl_lock);
  
  		if (di->lease_gen == gen &&
  		    time_before(jiffies, ttl) &&
  		    time_before(jiffies, di->time))
  			return true;
  	}
  	di->lease_gen = 0;
  	return false;
  }

  static int dentry_lease_is_valid(struct dentry *dentry, unsigned int flags)

  {
  	struct ceph_dentry_info *di;

  	struct ceph_mds_session *session = NULL;

  	u32 seq = 0;

  	int valid = 0;

  
  	spin_lock(&dentry->d_lock);
  	di = ceph_dentry(dentry);

  	if (di && __dentry_lease_is_valid(di)) {
  		valid = 1;

  		if (di->lease_renew_after &&
  		    time_after(jiffies, di->lease_renew_after)) {
  			/*
  			 * We should renew. If we're in RCU walk mode
  			 * though, we can't do that so just return
  			 * -ECHILD.
  			 */
  			if (flags & LOOKUP_RCU) {
  				valid = -ECHILD;
  			} else {
  				session = ceph_get_mds_session(di->lease_session);
  				seq = di->lease_seq;
  				di->lease_renew_after = 0;
  				di->lease_renew_from = jiffies;

  			}

  		}
  	}
  	spin_unlock(&dentry->d_lock);
  
  	if (session) {

  		ceph_mdsc_lease_send_msg(session, dentry,

  					 CEPH_MDS_LEASE_RENEW, seq);
  		ceph_put_mds_session(session);
  	}
  	dout("dentry_lease_is_valid - dentry %p = %d
  ", dentry, valid);
  	return valid;
  }
  
  /*

   * Called under dentry->d_lock.
   */
  static int __dir_lease_try_check(const struct dentry *dentry)
  {
  	struct ceph_dentry_info *di = ceph_dentry(dentry);
  	struct inode *dir;
  	struct ceph_inode_info *ci;
  	int valid = 0;
  
  	if (!di->lease_shared_gen)
  		return 0;
  	if (IS_ROOT(dentry))
  		return 0;
  
  	dir = d_inode(dentry->d_parent);
  	ci = ceph_inode(dir);
  
  	if (spin_trylock(&ci->i_ceph_lock)) {
  		if (atomic_read(&ci->i_shared_gen) == di->lease_shared_gen &&
  		    __ceph_caps_issued_mask(ci, CEPH_CAP_FILE_SHARED, 0))
  			valid = 1;
  		spin_unlock(&ci->i_ceph_lock);
  	} else {
  		valid = -EBUSY;
  	}
  
  	if (!valid)
  		di->lease_shared_gen = 0;
  	return valid;
  }
  
  /*

   * Check if directory-wide content lease/cap is valid.
   */

  static int dir_lease_is_valid(struct inode *dir, struct dentry *dentry,
  			      struct ceph_mds_client *mdsc)

  {
  	struct ceph_inode_info *ci = ceph_inode(dir);

  	int valid;
  	int shared_gen;

  	spin_lock(&ci->i_ceph_lock);

  	valid = __ceph_caps_issued_mask(ci, CEPH_CAP_FILE_SHARED, 1);

  	if (valid) {
  		__ceph_touch_fmode(ci, mdsc, CEPH_FILE_MODE_RD);
  		shared_gen = atomic_read(&ci->i_shared_gen);
  	}

  	spin_unlock(&ci->i_ceph_lock);

  	if (valid) {
  		struct ceph_dentry_info *di;
  		spin_lock(&dentry->d_lock);
  		di = ceph_dentry(dentry);
  		if (dir == d_inode(dentry->d_parent) &&
  		    di && di->lease_shared_gen == shared_gen)
  			__ceph_dentry_dir_lease_touch(di);
  		else
  			valid = 0;
  		spin_unlock(&dentry->d_lock);
  	}
  	dout("dir_lease_is_valid dir %p v%u dentry %p = %d
  ",
  	     dir, (unsigned)atomic_read(&ci->i_shared_gen), dentry, valid);

  	return valid;
  }
  
  /*
   * Check if cached dentry can be trusted.
   */

  static int ceph_d_revalidate(struct dentry *dentry, unsigned int flags)

  {

  	int valid = 0;

  	struct dentry *parent;

  	struct inode *dir, *inode;

  	struct ceph_mds_client *mdsc;

  	if (flags & LOOKUP_RCU) {

  		parent = READ_ONCE(dentry->d_parent);

  		dir = d_inode_rcu(parent);
  		if (!dir)
  			return -ECHILD;

  		inode = d_inode_rcu(dentry);

  	} else {
  		parent = dget_parent(dentry);
  		dir = d_inode(parent);

  		inode = d_inode(dentry);

  	}

  	dout("d_revalidate %p '%pd' inode %p offset 0x%llx
  ", dentry,

  	     dentry, inode, ceph_dentry(dentry)->offset);

  	mdsc = ceph_sb_to_client(dir->i_sb)->mdsc;

  	/* always trust cached snapped dentries, snapdir dentry */
  	if (ceph_snap(dir) != CEPH_NOSNAP) {

  		dout("d_revalidate %p '%pd' inode %p is SNAPPED
  ", dentry,

  		     dentry, inode);

  		valid = 1;

  	} else if (inode && ceph_snap(inode) == CEPH_SNAPDIR) {

  		valid = 1;

  	} else {

  		valid = dentry_lease_is_valid(dentry, flags);

  		if (valid == -ECHILD)
  			return valid;

  		if (valid || dir_lease_is_valid(dir, dentry, mdsc)) {

  			if (inode)
  				valid = ceph_is_any_caps(inode);

  			else
  				valid = 1;
  		}

  	}

  	if (!valid) {

  		struct ceph_mds_request *req;

  		int op, err;
  		u32 mask;

  		if (flags & LOOKUP_RCU)
  			return -ECHILD;

  		percpu_counter_inc(&mdsc->metric.d_lease_mis);

  		op = ceph_snap(dir) == CEPH_SNAPDIR ?

  			CEPH_MDS_OP_LOOKUPSNAP : CEPH_MDS_OP_LOOKUP;

  		req = ceph_mdsc_create_request(mdsc, op, USE_ANY_MDS);
  		if (!IS_ERR(req)) {
  			req->r_dentry = dget(dentry);

  			req->r_num_caps = 2;
  			req->r_parent = dir;

  
  			mask = CEPH_STAT_CAP_INODE | CEPH_CAP_AUTH_SHARED;
  			if (ceph_security_xattr_wanted(dir))
  				mask |= CEPH_CAP_XATTR_SHARED;

  			req->r_args.getattr.mask = cpu_to_le32(mask);

  			err = ceph_mdsc_do_request(mdsc, NULL, req);

  			switch (err) {
  			case 0:
  				if (d_really_is_positive(dentry) &&
  				    d_inode(dentry) == req->r_target_inode)
  					valid = 1;
  				break;
  			case -ENOENT:
  				if (d_really_is_negative(dentry))
  					valid = 1;

  				fallthrough;

  			default:
  				break;

  			}
  			ceph_mdsc_put_request(req);
  			dout("d_revalidate %p lookup result=%d
  ",
  			     dentry, err);
  		}

  	} else {
  		percpu_counter_inc(&mdsc->metric.d_lease_hit);

  	}

  	dout("d_revalidate %p %s
  ", dentry, valid ? "valid" : "invalid");

  	if (!valid)

  		ceph_dir_clear_complete(dir);

  	if (!(flags & LOOKUP_RCU))
  		dput(parent);

  	return valid;

  }
  
  /*

   * Delete unused dentry that doesn't have valid lease
   *
   * Called under dentry->d_lock.
   */
  static int ceph_d_delete(const struct dentry *dentry)
  {
  	struct ceph_dentry_info *di;
  
  	/* won't release caps */
  	if (d_really_is_negative(dentry))
  		return 0;
  	if (ceph_snap(d_inode(dentry)) != CEPH_NOSNAP)
  		return 0;
  	/* vaild lease? */
  	di = ceph_dentry(dentry);
  	if (di) {
  		if (__dentry_lease_is_valid(di))
  			return 0;
  		if (__dir_lease_try_check(dentry))
  			return 0;
  	}
  	return 1;
  }
  
  /*

   * Release our ceph_dentry_info.

   */

  static void ceph_d_release(struct dentry *dentry)

  {
  	struct ceph_dentry_info *di = ceph_dentry(dentry);

  	struct ceph_fs_client *fsc = ceph_sb_to_client(dentry->d_sb);

  	dout("d_release %p
  ", dentry);

  	atomic64_dec(&fsc->mdsc->metric.total_dentries);

  	spin_lock(&dentry->d_lock);

  	__dentry_lease_unlist(di);

  	dentry->d_fsdata = NULL;
  	spin_unlock(&dentry->d_lock);

  	if (di->lease_session)
  		ceph_put_mds_session(di->lease_session);
  	kmem_cache_free(ceph_dentry_cachep, di);

  }

  /*
   * When the VFS prunes a dentry from the cache, we need to clear the
   * complete flag on the parent directory.
   *
   * Called under dentry->d_lock.
   */
  static void ceph_d_prune(struct dentry *dentry)
  {

  	struct ceph_inode_info *dir_ci;
  	struct ceph_dentry_info *di;
  
  	dout("ceph_d_prune %pd %p
  ", dentry, dentry);

  
  	/* do we have a valid parent? */

  	if (IS_ROOT(dentry))

  		return;

  	/* we hold d_lock, so d_parent is stable */
  	dir_ci = ceph_inode(d_inode(dentry->d_parent));
  	if (dir_ci->i_vino.snap == CEPH_SNAPDIR)

  		return;

  	/* who calls d_delete() should also disable dcache readdir */
  	if (d_really_is_negative(dentry))

  		return;