path: root/fs/ceph/dir.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/ceph/ceph_debug.h>

#include <linux/spinlock.h>
#include <linux/fs_struct.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;

/*
 * Initialize ceph dentry state.
 */
static int ceph_d_init(struct dentry *dentry)
{
	struct ceph_dentry_info *di;

	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;
	ceph_dentry_lru_add(dentry);
	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'\n", 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\n", 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\n", 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\n", 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) {
			emit_dentry = true;
		}
		spin_unlock(&dentry->d_lock);

		if (emit_dentry) {
			dout(" %llx dentry %p %pd %p\n", di->offset,
			     dentry, dentry, d_inode(dentry));
			ctx->pos = di->offset;
			if (!dir_emit(ctx, dentry->d_name.name,
				      dentry->d_name.len,
				      ceph_translate_ino(dentry->d_sb,
							 d_inode(dentry)->i_ino),
				      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(stru