Merge tag 'gpio-for-v3.11-3' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw...

[linux-2.6.git] / fs / ceph / dir.c

#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 "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 inode_operations ceph_dir_iops;
const struct file_operations ceph_dir_fops;
const struct dentry_operations ceph_dentry_ops;

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

        if (dentry->d_fsdata)
                return 0;

        di = kmem_cache_alloc(ceph_dentry_cachep, GFP_NOFS | __GFP_ZERO);
        if (!di)
                return -ENOMEM;          /* oh well */

        spin_lock(&dentry->d_lock);
        if (dentry->d_fsdata) {
                /* lost a race */
                kmem_cache_free(ceph_dentry_cachep, di);
                goto out_unlock;
        }

        if (ceph_snap(dentry->d_parent->d_inode) == CEPH_NOSNAP)
                d_set_d_op(dentry, &ceph_dentry_ops);
        else if (ceph_snap(dentry->d_parent->d_inode) == CEPH_SNAPDIR)
                d_set_d_op(dentry, &ceph_snapdir_dentry_ops);
        else
                d_set_d_op(dentry, &ceph_snap_dentry_ops);

        di->dentry = dentry;
        di->lease_session = NULL;
        dentry->d_time = jiffies;
        /* avoid reordering d_fsdata setup so that the check above is safe */
        smp_mb();
        dentry->d_fsdata = di;
        ceph_dentry_lru_add(dentry);
out_unlock:
        spin_unlock(&dentry->d_lock);
        return 0;
}

struct inode *ceph_get_dentry_parent_inode(struct dentry *dentry)
{
        struct inode *inode = NULL;

        if (!dentry)
                return NULL;

        spin_lock(&dentry->d_lock);
        if (!IS_ROOT(dentry)) {
                inode = dentry->d_parent->d_inode;
                ihold(inode);
        }
        spin_unlock(&dentry->d_lock);
        return inode;
}


/*
 * for readdir, we encode the directory frag and offset within that
 * frag into f_pos.
 */
static unsigned fpos_frag(loff_t p)
{
        return p >> 32;
}
static unsigned fpos_off(loff_t p)
{
        return p & 0xffffffff;
}

/*
 * When possible, we try to satisfy a readdir by peeking at the
 * dcache.  We make this work by carefully ordering dentries on
 * d_u.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)
{
        struct ceph_file_info *fi = file->private_data;
        struct dentry *parent = file->f_dentry;
        struct inode *dir = parent->d_inode;
        struct list_head *p;
        struct dentry *dentry, *last;
        struct ceph_dentry_info *di;
        int err = 0;

        /* claim ref on last dentry we returned */
        last = fi->dentry;
        fi->dentry = NULL;

        dout("__dcache_readdir %p at %llu (last %p)\n", dir, ctx->pos,
             last);

        spin_lock(&parent->d_lock);

        /* start at beginning? */
        if (ctx->pos == 2 || last == NULL ||
            ctx->pos < ceph_dentry(last)->offset) {
                if (list_empty(&parent->d_subdirs))
                        goto out_unlock;
                p = parent->d_subdirs.prev;
                dout(" initial p %p/%p\n", p->prev, p->next);
        } else {
                p = last->d_u.d_child.prev;
        }

more:
        dentry = list_entry(p, struct dentry, d_u.d_child);
        di = ceph_dentry(dentry);
        while (1) {
                dout(" p %p/%p %s d_subdirs %p/%p\n", p->prev, p->next,
                     d_unhashed(dentry) ? "!hashed" : "hashed",
                     parent->d_subdirs.prev, parent->d_subdirs.next);
                if (p == &parent->d_subdirs) {
                        fi->flags |= CEPH_F_ATEND;
                        goto out_unlock;
                }
                spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
                if (!d_unhashed(dentry) && dentry->d_inode &&
                    ceph_snap(dentry->d_inode) != CEPH_SNAPDIR &&
                    ceph_ino(dentry->d_inode) != CEPH_INO_CEPH &&
                    ctx->pos <= di->offset)
                        break;
                dout(" skipping %p %.*s at %llu (%llu)%s%s\n", dentry,
                     dentry->d_name.len, dentry->d_name.name, di->offset,
                     ctx->pos, d_unhashed(dentry) ? " unhashed" : "",
                     !dentry->d_inode ? " null" : "");
                spin_unlock(&dentry->d_lock);
                p = p->prev;
                dentry = list_entry(p, struct dentry, d_u.d_child);
                di = ceph_dentry(dentry);
        }

        dget_dlock(dentry);
        spin_unlock(&dentry->d_lock);
        spin_unlock(&parent->d_lock);

        dout(" %llu (%llu) dentry %p %.*s %p\n", di->offset, ctx->pos,
             dentry, dentry->d_name.len, dentry->d_name.name, dentry->d_inode);
        ctx->pos = di->offset;
        if (!dir_emit(ctx, dentry->d_name.name,
                      dentry->d_name.len,
                      ceph_translate_ino(dentry->d_sb, dentry->d_inode->i_ino),
                      dentry->d_inode->i_mode >> 12)) {
                if (last) {
                        /* remember our position */
                        fi->dentry = last;
                        fi->next_offset = di->offset;
                }
                dput(dentry);
                return 0;
        }

        if (last)
                dput(last);
        last = dentry;

        ctx->pos++;

        /* make sure a dentry wasn't dropped while we didn't have parent lock */
        if (!ceph_dir_is_complete(dir)) {
                dout(" lost dir complete on %p; falling back to mds\n", dir);
                err = -EAGAIN;
                goto out;
        }

        spin_lock(&parent->d_lock);
        p = p->prev;    /* advance to next dentry */
        goto more;

out_unlock:
        spin_unlock(&parent->d_lock);
out:
        if (last)
                dput(last);
        return err;
}

/*
 * 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_file_info *fi, const char *name,
                            int len)
{
        kfree(fi->last_name);
        fi->last_name = kmalloc(len+1, GFP_NOFS);
        if (!fi->last_name)
                return -ENOMEM;
        memcpy(fi->last_name, name, len);
        fi->last_name[len] = 0;
        dout("note_last_dentry '%s'\n", fi->last_name);
        return 0;
}

static int ceph_readdir(struct file *file, struct dir_context *ctx)
{
        struct ceph_file_info *fi = 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;
        unsigned frag = fpos_frag(ctx->pos);
        int off = fpos_off(ctx->pos);
        int err;
        u32 ftype;
        struct ceph_mds_reply_info_parsed *rinfo;
        const int max_entries = fsc->mount_options->max_readdir;
        const int max_bytes = fsc->mount_options->max_readdir_bytes;

        dout("readdir %p file %p frag %u off %u\n", inode, file, frag, off);
        if (fi->flags & CEPH_F_ATEND)
                return 0;

        /* always start with . and .. */
        if (ctx->pos == 0) {
                /* note dir version at start of readdir so we can tell
                 * if any dentries get dropped */
                fi->dir_release_count = atomic_read(&ci->i_release_count);

                dout("readdir off 0 -> '.'\n");
                if (!dir_emit(ctx, ".", 1, 
                            ceph_translate_ino(inode->i_sb, inode->i_ino),
                            inode->i_mode >> 12))
                        return 0;
                ctx->pos = 1;
                off = 1;
        }
        if (ctx->pos == 1) {
                ino_t ino = parent_ino(file->f_dentry);
                dout("readdir off 1 -> '..'\n");
                if (!dir_emit(ctx, "..", 2,
                            ceph_translate_ino(inode->i_sb, ino),
                            inode->i_mode >> 12))
                        return 0;
                ctx->pos = 2;
                off = 2;
        }

        /* can we use the dcache? */
        spin_lock(&ci->i_ceph_lock);
        if ((ctx->pos == 2 || fi->dentry) &&
            !ceph_test_mount_opt(fsc, NOASYNCREADDIR) &&
            ceph_snap(inode) != CEPH_SNAPDIR &&
            __ceph_dir_is_complete(ci) &&
            __ceph_caps_issued_mask(ci, CEPH_CAP_FILE_SHARED, 1)) {
                spin_unlock(&ci->i_ceph_lock);
                err = __dcache_readdir(file, ctx);
                if (err != -EAGAIN)
                        return err;
        } else {
                spin_unlock(&ci->i_ceph_lock);
        }
        if (fi->dentry) {
                err = note_last_dentry(fi, fi->dentry->d_name.name,
                                       fi->dentry->d_name.len);
                if (err)
                        return err;
                dput(fi->dentry);
                fi->dentry = NULL;
        }

        /* proceed with a normal readdir */

more:
        /* do we have the correct frag content buffered? */
        if (fi->frag != frag || fi->last_readdir == NULL) {
                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 (fi->last_readdir) {
                        ceph_mdsc_put_request(fi->last_readdir);
                        fi->last_readdir = NULL;
                }

                /* requery frag tree, as the frag topology may have changed */
                frag = ceph_choose_frag(ceph_inode(inode), frag, NULL, NULL);

                dout("readdir fetching %llx.%llx frag %x offset '%s'\n",
                     ceph_vinop(inode), frag, fi->last_name);
                req = ceph_mdsc_create_request(mdsc, op, USE_AUTH_MDS);
                if (IS_ERR(req))
                        return PTR_ERR(req);
                req->r_inode = inode;
                ihold(inode);
                req->r_dentry = dget(file->f_dentry);
                /* hints to request -> mds selection code */
                req->r_direct_mode = USE_AUTH_MDS;
                req->r_direct_hash = ceph_frag_value(frag);
                req->r_direct_is_hash = true;
                req->r_path2 = kstrdup(fi->last_name, GFP_NOFS);
                req->r_readdir_offset = fi->next_offset;
                req->r_args.readdir.frag = cpu_to_le32(frag);
                req->r_args.readdir.max_entries = cpu_to_le32(max_entries);
                req->r_args.readdir.max_bytes = cpu_to_le32(max_bytes);
                req->r_num_caps = max_entries + 1;
                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\n", err, frag,
                     (int)req->r_reply_info.dir_end,
                     (int)req->r_reply_info.dir_complete);

                if (!req->r_did_prepopulate) {
                        dout("readdir !did_prepopulate");
                        /* preclude from marking dir complete */
                        fi->dir_release_count--;
                }

                /* note next offset and last dentry name */
                fi->offset = fi->next_offset;
                fi->last_readdir = req;

                if (req->r_reply_info.dir_end) {
                        kfree(fi->last_name);
                        fi->last_name = NULL;
                        if (ceph_frag_is_rightmost(frag))
                                fi->next_offset = 2;
                        else
                                fi->next_offset = 0;
                } else {
                        rinfo = &req->r_reply_info;
                        err = note_last_dentry(fi,
                                       rinfo->dir_dname[rinfo->dir_nr-1],
                                       rinfo->dir_dname_len[rinfo->dir_nr-1]);
                        if (err)
                                return err;
                        fi->next_offset += rinfo->dir_nr;
                }
        }

        rinfo = &fi->last_readdir->r_reply_info;
        dout("readdir frag %x num %d off %d chunkoff %d\n", frag,
             rinfo->dir_nr, off, fi->offset);

        ctx->pos = ceph_make_fpos(frag, off);
        while (off >= fi->offset && off - fi->offset < rinfo->dir_nr) {
                struct ceph_mds_reply_inode *in =
                        rinfo->dir_in[off - fi->offset].in;
                struct ceph_vino vino;
                ino_t ino;

                dout("readdir off %d (%d/%d) -> %lld '%.*s' %p\n",
                     off, off - fi->offset, rinfo->dir_nr, ctx->pos,
                     rinfo->dir_dname_len[off - fi->offset],
                     rinfo->dir_dname[off - fi->offset], in);
                BUG_ON(!in);
                ftype = le32_to_cpu(in->mode) >> 12;
                vino.ino = le64_to_cpu(in->ino);
                vino.snap = le64_to_cpu(in->snapid);
                ino = ceph_vino_to_ino(vino);
                if (!dir_emit(ctx,
                            rinfo->dir_dname[off - fi->offset],
                            rinfo->dir_dname_len[off - fi->offset],
                            ceph_translate_ino(inode->i_sb, ino), ftype)) {
                        dout("filldir stopping us...\n");
                        return 0;
                }
                off++;
                ctx->pos++;
        }

        if (fi->last_name) {
                ceph_mdsc_put_request(fi->last_readdir);
                fi->last_readdir = NULL;
                goto more;
        }

        /* more frags? */
        if (!ceph_frag_is_rightmost(frag)) {
                frag = ceph_frag_next(frag);
                off = 0;
                ctx->pos = ceph_make_fpos(frag, off);
                dout("readdir next frag is %x\n", frag);
                goto more;
        }
        fi->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.
         */
        spin_lock(&ci->i_ceph_lock);
        if (atomic_read(&ci->i_release_count) == fi->dir_release_count) {
                dout(" marking %p complete\n", inode);
                __ceph_dir_set_complete(ci, fi->dir_release_count);
                ci->i_max_offset = ctx->pos;
        }
        spin_unlock(&ci->i_ceph_lock);

        dout("readdir %p file %p done.\n", inode, file);
        return 0;
}

static void reset_readdir(struct ceph_file_info *fi)
{
        if (fi->last_readdir) {
                ceph_mdsc_put_request(fi->last_readdir);
                fi->last_readdir = NULL;
        }
        kfree(fi->last_name);
        fi->last_name = NULL;
        fi->next_offset = 2;  /* compensate for . and .. */
        if (fi->dentry) {
                dput(fi->dentry);
                fi->dentry = NULL;
        }
        fi->flags &= ~CEPH_F_ATEND;
}

static loff_t ceph_dir_llseek(struct file *file, loff_t offset, int whence)
{
        struct ceph_file_info *fi = file->private_data;
        struct inode *inode = file->f_mapping->host;
        loff_t old_offset = offset;
        loff_t retval;

        mutex_lock(&inode->i_mutex);
        retval = -EINVAL;
        switch (whence) {
        case SEEK_END:
                offset += inode->i_size + 2;   /* FIXME */
                break;
        case SEEK_CUR:
                offset += file->f_pos;
        case SEEK_SET:
                break;
        default:
                goto out;
        }

        if (offset >= 0 && offset <= inode->i_sb->s_maxbytes) {
                if (offset != file->f_pos) {
                        file->f_pos = offset;
                        file->f_version = 0;
                        fi->flags &= ~CEPH_F_ATEND;
                }
                retval = offset;

                /*
                 * discard buffered readdir content on seekdir(0), or
                 * seek to new frag, or seek prior to current chunk.
                 */
                if (offset == 0 ||
                    fpos_frag(offset) != fpos_frag(old_offset) ||
                    fpos_off(offset) < fi->offset) {
                        dout("dir_llseek dropping %p content\n", file);
                        reset_readdir(fi);
                }

                /* bump dir_release_count if we did a forward seek */
                if (offset > old_offset)
                        fi->dir_release_count--;
        }
out:
        mutex_unlock(&inode->i_mutex);
        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 = dentry->d_parent->d_inode; /* 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 '%.*s', linking to snapdir %p\n",
                     dentry, dentry->d_name.len, dentry->d_name.name, 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\n",
                             dentry, dentry->d_inode);
                        if (dentry->d_inode) {
                                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 int 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 = fsc->mdsc;
        struct ceph_mds_request *req;
        int op;
        int err;

        dout("lookup %p dentry %p '%.*s'\n",
             dir, dentry, dentry->d_name.len, dentry->d_name.name);

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

        err = ceph_init_dentry(dentry);
        if (err < 0)
                return ERR_PTR(err);

        /* can we conclude ENOENT locally? */
        if (dentry->d_inode == NULL) {
                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 %d\n", 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_dir_is_complete(ci) &&
                    (__ceph_caps_issued_mask(ci, CEPH_CAP_FILE_SHARED, 1))) {
                        spin_unlock(&ci->i_ceph_lock);
                        dout(" dir %p complete, -ENOENT\n", dir);
                        d_add(dentry, NULL);
                        di->lease_shared_gen = 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;
        /* we only need inode linkage */
        req->r_args.getattr.mask = cpu_to_le32(CEPH_STAT_CAP_INODE);
        req->r_locked_dir = dir;
        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\n", 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).  Link our
                 * dentry to that inode, but don't hash it, just in
                 * case the VFS wants to dereference it.
                 */
                BUG_ON(!result->d_inode);
                d_instantiate(dentry, result->d_inode);
                return 0;
        }
        return PTR_ERR(result);
}

static int ceph_mknod(struct inode *dir, struct dentry *dentry,
                      umode_t mode, dev_t rdev)
{
        struct ceph_fs_client *fsc = ceph_sb_to_client(dir->i_sb);
        struct ceph_mds_client *mdsc = fsc->mdsc;
        struct ceph_mds_request *req;
        int err;

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

        dout("mknod in dir %p dentry %p mode 0%ho rdev %d\n",
             dir, dentry, mode, rdev);
        req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_MKNOD, 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_locked_dir = dir;
        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;
        req->r_dentry_unless = CEPH_CAP_FILE_EXCL;
        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);
        if (err)
                d_drop(dentry);
        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_fs_client *fsc = ceph_sb_to_client(dir->i_sb);
        struct ceph_mds_client *mdsc = fsc->mdsc;
        struct ceph_mds_request *req;
        int err;

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

        dout("symlink in dir %p dentry %p to '%s'\n", dir, dentry, dest);
        req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_SYMLINK, 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_path2 = kstrdup(dest, GFP_NOFS);
        req->r_locked_dir = dir;
        req->r_dentry_drop = CEPH_CAP_FILE_SHARED;
        req->r_dentry_unless = CEPH_CAP_FILE_EXCL;
        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);
        if (err)
                d_drop(dentry);
        return err;
}

static int ceph_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
        struct ceph_fs_client *fsc = ceph_sb_to_client(dir->i_sb);
        struct ceph_mds_client *mdsc = fsc->mdsc;
        struct ceph_mds_request *req;
        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 '%.*s' dn %p\n", dir,
                     dentry->d_name.len, dentry->d_name.name, dentry);
        } else if (ceph_snap(dir) == CEPH_NOSNAP) {
                dout("mkdir dir %p dn %p mode 0%ho\n", dir, dentry, mode);
                op = CEPH_MDS_OP_MKDIR;
        } else {
                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_locked_dir = dir;
        req->r_args.mkdir.mode = cpu_to_le32(mode);
        req->r_dentry_drop = CEPH_CAP_FILE_SHARED;
        req->r_dentry_unless = CEPH_CAP_FILE_EXCL;
        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 < 0)
                d_drop(dentry);
        return err;
}

static int ceph_link(struct dentry *old_dentry, 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 ceph_mds_request *req;
        int err;

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

        dout("link in dir %p old_dentry %p dentry %p\n", 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); /* or inode? hrm. */
        req->r_old_dentry_dir = ceph_get_dentry_parent_inode(old_dentry);
        req->r_locked_dir = dir;
        req->r_dentry_drop = CEPH_CAP_FILE_SHARED;
        req->r_dentry_unless = CEPH_CAP_FILE_EXCL;
        err = ceph_mdsc_do_request(mdsc, dir, req);
        if (err) {
                d_drop(dentry);
        } else if (!req->r_reply_info.head->is_dentry) {
                ihold(old_dentry->d_inode);
                d_instantiate(dentry, old_dentry->d_inode);
        }
        ceph_mdsc_put_request(req);
        return err;
}

/*
 * For a soon-to-be unlinked file, drop the AUTH_RDCACHE caps.  If it
 * looks like the link count will hit 0, drop any other caps (other
 * than PIN) we don't specifically want (due to the file still being
 * open).
 */
static int drop_caps_for_unlink(struct inode *inode)
{
        struct ceph_inode_info *ci = ceph_inode(inode);
        int drop = CEPH_CAP_LINK_SHARED | CEPH_CAP_LINK_EXCL;

        spin_lock(&ci->i_ceph_lock);
        if (inode->i_nlink == 1) {
                drop |= ~(__ceph_caps_wanted(ci) | CEPH_CAP_PIN);
                ci->i_ceph_flags |= CEPH_I_NODELAY;
        }
        spin_unlock(&ci->i_ceph_lock);
        return drop;
}

/*
 * 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 = dentry->d_inode;
        struct ceph_mds_request *req;
        int err = -EROFS;
        int op;

        if (ceph_snap(dir) == CEPH_SNAPDIR) {
                /* rmdir .snap/foo is RMSNAP */
                dout("rmsnap dir %p '%.*s' dn %p\n", dir, dentry->d_name.len,
                     dentry->d_name.name, dentry);
                op = CEPH_MDS_OP_RMSNAP;
        } else if (ceph_snap(dir) == CEPH_NOSNAP) {
                dout("unlink/rmdir dir %p dn %p inode %p\n",
                     dir, dentry, inode);
                op = S_ISDIR(dentry->d_inode->i_mode) ?
                        CEPH_MDS_OP_RMDIR : CEPH_MDS_OP_UNLINK;
        } else
                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_locked_dir = dir;
        req->r_dentry_drop = CEPH_CAP_FILE_SHARED;
        req->r_dentry_unless = CEPH_CAP_FILE_EXCL;
        req->r_inode_drop = drop_caps_for_unlink(inode);
        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)
{
        struct ceph_fs_client *fsc = ceph_sb_to_client(old_dir->i_sb);
        struct ceph_mds_client *mdsc = fsc->mdsc;
        struct ceph_mds_request *req;
        int err;

        if (ceph_snap(old_dir) != ceph_snap(new_dir))
                return -EXDEV;
        if (ceph_snap(old_dir) != CEPH_NOSNAP ||
            ceph_snap(new_dir) != CEPH_NOSNAP)
                return -EROFS;
        dout("rename dir %p dentry %p to dir %p dentry %p\n",
             old_dir, old_dentry, new_dir, new_dentry);
        req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_RENAME, USE_AUTH_MDS);
        if (IS_ERR(req))
                return PTR_ERR(req);
        req->r_dentry = dget(new_dentry);
        req->r_num_caps = 2;
        req->r_old_dentry = dget(old_dentry);
        req->r_old_dentry_dir = ceph_get_dentry_parent_inode(old_dentry);
        req->r_locked_dir = new_dir;
        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;
        if (new_dentry->d_inode)
                req->r_inode_drop = drop_caps_for_unlink(new_dentry->d_inode);
        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 screws up d_subdirs order */
                ceph_dir_clear_complete(new_dir);

                d_move(old_dentry, new_dentry);

                /* ensure target dentry is invalidated, despite
                   rehashing bug in vfs_rename_dir */
                ceph_invalidate_dentry_lease(new_dentry);
        }
        ceph_mdsc_put_request(req);
        return err;
}

/*
 * Ensure a dentry lease will no longer revalidate.
 */
void ceph_invalidate_dentry_lease(struct dentry *dentry)
{
        spin_lock(&dentry->d_lock);
        dentry->d_time = jiffies;
        ceph_dentry(dentry)->lease_shared_gen = 0;
        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 int dentry_lease_is_valid(struct dentry *dentry)
{
        struct ceph_dentry_info *di;
        struct ceph_mds_session *s;
        int valid = 0;
        u32 gen;
        unsigned long ttl;
        struct ceph_mds_session *session = NULL;
        struct inode *dir = NULL;
        u32 seq = 0;

        spin_lock(&dentry->d_lock);
        di = ceph_dentry(dentry);
        if (di->lease_session) {
                s = di->lease_session;
                spin_lock(&s->s_gen_ttl_lock);
                gen = s->s_cap_gen;
                ttl = s->s_cap_ttl;
                spin_unlock(&s->s_gen_ttl_lock);

                if (di->lease_gen == gen &&
                    time_before(jiffies, dentry->d_time) &&
                    time_before(jiffies, ttl)) {
                        valid = 1;
                        if (di->lease_renew_after &&
                            time_after(jiffies, di->lease_renew_after)) {
                                /* we should renew */
                                dir = dentry->d_parent->d_inode;
                                session = ceph_get_mds_session(s);
                                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, dir, dentry,
                                         CEPH_MDS_LEASE_RENEW, seq);
                ceph_put_mds_session(session);
        }
        dout("dentry_lease_is_valid - dentry %p = %d\n", dentry, valid);
        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_inode_info *ci = ceph_inode(dir);
        struct ceph_dentry_info *di = ceph_dentry(dentry);
        int valid = 0;

        spin_lock(&ci->i_ceph_lock);
        if (ci->i_shared_gen == di->lease_shared_gen)
                valid = __ceph_caps_issued_mask(ci, CEPH_CAP_FILE_SHARED, 1);
        spin_unlock(&ci->i_ceph_lock);
        dout("dir_lease_is_valid dir %p v%u dentry %p v%u = %d\n",
             dir, (unsigned)ci->i_shared_gen, dentry,
             (unsigned)di->lease_shared_gen, 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 inode *dir;

        if (flags & LOOKUP_RCU)
                return -ECHILD;

        dout("d_revalidate %p '%.*s' inode %p offset %lld\n", dentry,
             dentry->d_name.len, dentry->d_name.name, dentry->d_inode,
             ceph_dentry(dentry)->offset);

        dir = ceph_get_dentry_parent_inode(dentry);

        /* always trust cached snapped dentries, snapdir dentry */
        if (ceph_snap(dir) != CEPH_NOSNAP) {
                dout("d_revalidate %p '%.*s' inode %p is SNAPPED\n", dentry,
                     dentry->d_name.len, dentry->d_name.name, dentry->d_inode);
                valid = 1;
        } else if (dentry->d_inode &&
                   ceph_snap(dentry->d_inode) == CEPH_SNAPDIR) {
                valid = 1;
        } else if (dentry_lease_is_valid(dentry) ||
                   dir_lease_is_valid(dir, dentry)) {
                valid = 1;
        }

        dout("d_revalidate %p %s\n", dentry, valid ? "valid" : "invalid");
        if (valid)
                ceph_dentry_lru_touch(dentry);
        else
                d_drop(dentry);
        iput(dir);
        return valid;
}

/*
 * Release our ceph_dentry_info.
 */
static void ceph_d_release(struct dentry *dentry)
{
        struct ceph_dentry_info *di = ceph_dentry(dentry);

        dout("d_release %p\n", dentry);
        ceph_dentry_lru_del(dentry);
        if (di->lease_session)
                ceph_put_mds_session(di->lease_session);
        kmem_cache_free(ceph_dentry_cachep, di);
        dentry->d_fsdata = NULL;
}

static int ceph_snapdir_d_revalidate(struct dentry *dentry,
                                          unsigned int flags)
{
        /*
         * Eventually, we'll want to revalidate snapped metadata
         * too... probably...
         */
        return 1;
}

/*
 * 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)
{
        dout("ceph_d_prune %p\n", dentry);

        /* do we have a valid parent? */
        if (IS_ROOT(dentry))
                return;

        /* if we are not hashed, we don't affect dir's completeness */
        if (d_unhashed(dentry))
                return;

        /*
         * we hold d_lock, so d_parent is stable, and d_fsdata is never
         * cleared until d_release
         */
        ceph_dir_clear_complete(dentry->d_parent->d_inode);
}

/*
 * read() on a dir.  This weird interface hack only works if mounted
 * with '-o dirstat'.
 */
static ssize_t ceph_read_dir(struct file *file, char __user *buf, size_t size,
                             loff_t *ppos)
{
        struct ceph_file_info *cf = file->private_data;
        struct inode *inode = file_inode(file);
        struct ceph_inode_info *ci = ceph_inode(inode);
        int left;
        const int bufsize = 1024;

        if (!ceph_test_mount_opt(ceph_sb_to_client(inode->i_sb), DIRSTAT))
                return -EISDIR;

        if (!cf->dir_info) {
                cf->dir_info = kmalloc(bufsize, GFP_NOFS);
                if (!cf->dir_info)
                        return -ENOMEM;
                cf->dir_info_len =
                        snprintf(cf->dir_info, bufsize,
                                "entries:   %20lld\n"
                                " files:    %20lld\n"
                                " subdirs:  %20lld\n"
                                "rentries:  %20lld\n"
                                " rfiles:   %20lld\n"
                                " rsubdirs: %20lld\n"
                                "rbytes:    %20lld\n"
                                "rctime:    %10ld.%09ld\n",
                                ci->i_files + ci->i_subdirs,
                                ci->i_files,
                                ci->i_subdirs,
                                ci->i_rfiles + ci->i_rsubdirs,
                                ci->i_rfiles,
                                ci->i_rsubdirs,
                                ci->i_rbytes,
                                (long)ci->i_rctime.tv_sec,
                                (long)ci->i_rctime.tv_nsec);
        }

        if (*ppos >= cf->dir_info_len)
                return 0;
        size = min_t(unsigned, size, cf->dir_info_len-*ppos);
        left = copy_to_user(buf, cf->dir_info + *ppos, size);
        if (left == size)
                return -EFAULT;
        *ppos += (size - left);
        return size - left;
}

/*
 * an fsync() on a dir will wait for any uncommitted directory
 * operations to commit.
 */
static int ceph_dir_fsync(struct file *file, loff_t start, loff_t end,
                          int datasync)
{
        struct inode *inode = file_inode(file);
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct list_head *head = &ci->i_unsafe_dirops;
        struct ceph_mds_request *req;
        u64 last_tid;
        int ret = 0;

        dout("dir_fsync %p\n", inode);
        ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
        if (ret)
                return ret;
        mutex_lock(&inode->i_mutex);

        spin_lock(&ci->i_unsafe_lock);
        if (list_empty(head))
                goto out;

        req = list_entry(head->prev,
                         struct ceph_mds_request, r_unsafe_dir_item);
        last_tid = req->r_tid;

        do {
                ceph_mdsc_get_request(req);
                spin_unlock(&ci->i_unsafe_lock);

                dout("dir_fsync %p wait on tid %llu (until %llu)\n",
                     inode, req->r_tid, last_tid);
                if (req->r_timeout) {
                        ret = wait_for_completion_timeout(
                                &req->r_safe_completion, req->r_timeout);
                        if (ret > 0)
                                ret = 0;
                        else if (ret == 0)
                                ret = -EIO;  /* timed out */
                } else {
                        wait_for_completion(&req->r_safe_completion);
                }
                ceph_mdsc_put_request(req);

                spin_lock(&ci->i_unsafe_lock);
                if (ret || list_empty(head))
                        break;
                req = list_entry(head->next,
                                 struct ceph_mds_request, r_unsafe_dir_item);
        } while (req->r_tid < last_tid);
out:
        spin_unlock(&ci->i_unsafe_lock);
        mutex_unlock(&inode->i_mutex);

        return ret;
}

/*
 * We maintain a private dentry LRU.
 *
 * FIXME: this needs to be changed to a per-mds lru to be useful.
 */
void ceph_dentry_lru_add(struct dentry *dn)
{
        struct ceph_dentry_info *di = ceph_dentry(dn);
        struct ceph_mds_client *mdsc;

        dout("dentry_lru_add %p %p '%.*s'\n", di, dn,
             dn->d_name.len, dn->d_name.name);
        mdsc = ceph_sb_to_client(dn->d_sb)->mdsc;
        spin_lock(&mdsc->dentry_lru_lock);
        list_add_tail(&di->lru, &mdsc->dentry_lru);
        mdsc->num_dentry++;
        spin_unlock(&mdsc->dentry_lru_lock);
}

void ceph_dentry_lru_touch(struct dentry *dn)
{
        struct ceph_dentry_info *di = ceph_dentry(dn);
        struct ceph_mds_client *mdsc;

        dout("dentry_lru_touch %p %p '%.*s' (offset %lld)\n", di, dn,
             dn->d_name.len, dn->d_name.name, di->offset);
        mdsc = ceph_sb_to_client(dn->d_sb)->mdsc;
        spin_lock(&mdsc->dentry_lru_lock);
        list_move_tail(&di->lru, &mdsc->dentry_lru);
        spin_unlock(&mdsc->dentry_lru_lock);
}

void ceph_dentry_lru_del(struct dentry *dn)
{
        struct ceph_dentry_info *di = ceph_dentry(dn);
        struct ceph_mds_client *mdsc;

        dout("dentry_lru_del %p %p '%.*s'\n", di, dn,
             dn->d_name.len, dn->d_name.name);
        mdsc = ceph_sb_to_client(dn->d_sb)->mdsc;
        spin_lock(&mdsc->dentry_lru_lock);
        list_del_init(&di->lru);
        mdsc->num_dentry--;
        spin_unlock(&mdsc->dentry_lru_lock);
}

/*
 * Return name hash for a given dentry.  This is dependent on
 * the parent directory's hash function.
 */
unsigned ceph_dentry_hash(struct inode *dir, struct dentry *dn)
{
        struct ceph_inode_info *dci = ceph_inode(dir);

        switch (dci->i_dir_layout.dl_dir_hash) {
        case 0: /* for backward compat */
        case CEPH_STR_HASH_LINUX:
                return dn->d_name.hash;

        default:
                return ceph_str_hash(dci->i_dir_layout.dl_dir_hash,
                                     dn->d_name.name, dn->d_name.len);
        }
}

const struct file_operations ceph_dir_fops = {
        .read = ceph_read_dir,
        .iterate = ceph_readdir,
        .llseek = ceph_dir_llseek,
        .open = ceph_open,
        .release = ceph_release,
        .unlocked_ioctl = ceph_ioctl,
        .fsync = ceph_dir_fsync,
};

const struct inode_operations ceph_dir_iops = {
        .lookup = ceph_lookup,
        .permission = ceph_permission,
        .getattr = ceph_getattr,
        .setattr = ceph_setattr,
        .setxattr = ceph_setxattr,
        .getxattr = ceph_getxattr,
        .listxattr = ceph_listxattr,
        .removexattr = ceph_removexattr,
        .mknod = ceph_mknod,
        .symlink = ceph_symlink,
        .mkdir = ceph_mkdir,
        .link = ceph_link,
        .unlink = ceph_unlink,
        .rmdir = ceph_unlink,
        .rename = ceph_rename,
        .create = ceph_create,
        .atomic_open = ceph_atomic_open,
};

const struct dentry_operations ceph_dentry_ops = {
        .d_revalidate = ceph_d_revalidate,
        .d_release = ceph_d_release,
        .d_prune = ceph_d_prune,
};

const struct dentry_operations ceph_snapdir_dentry_ops = {
        .d_revalidate = ceph_snapdir_d_revalidate,
        .d_release = ceph_d_release,
};

const struct dentry_operations ceph_snap_dentry_ops = {
        .d_release = ceph_d_release,
        .d_prune = ceph_d_prune,
};