#define pr_fmt(fmt) "drbd debugfs: " fmt
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/stat.h>
#include <linux/jiffies.h>
#include <linux/list.h>

#include "drbd_int.h"
#include "drbd_req.h"
#include "drbd_debugfs.h"


/**********************************************************************
 * Whenever you change the file format, remember to bump the version. *
 **********************************************************************/

static struct dentry *drbd_debugfs_root;
static struct dentry *drbd_debugfs_version;
static struct dentry *drbd_debugfs_resources;
static struct dentry *drbd_debugfs_minors;

static void seq_print_age_or_dash(struct seq_file *m, bool valid, unsigned long dt)
{
        if (valid)
                seq_printf(m, "\t%d", jiffies_to_msecs(dt));
        else
                seq_printf(m, "\t-");
}

static void __seq_print_rq_state_bit(struct seq_file *m,
        bool is_set, char *sep, const char *set_name, const char *unset_name)
{
        if (is_set && set_name) {
                seq_putc(m, *sep);
                seq_puts(m, set_name);
                *sep = '|';
        } else if (!is_set && unset_name) {
                seq_putc(m, *sep);
                seq_puts(m, unset_name);
                *sep = '|';
        }
}

static void seq_print_rq_state_bit(struct seq_file *m,
        bool is_set, char *sep, const char *set_name)
{
        __seq_print_rq_state_bit(m, is_set, sep, set_name, NULL);
}

/* pretty print enum drbd_req_state_bits req->rq_state */
static void seq_print_request_state(struct seq_file *m, struct drbd_request *req)
{
        unsigned int s = req->rq_state;
        char sep = ' ';
        seq_printf(m, "\t0x%08x", s);
        seq_printf(m, "\tmaster: %s", req->master_bio ? "pending" : "completed");

        /* RQ_WRITE ignored, already reported */
        seq_puts(m, "\tlocal:");
        seq_print_rq_state_bit(m, s & RQ_IN_ACT_LOG, &sep, "in-AL");
        seq_print_rq_state_bit(m, s & RQ_POSTPONED, &sep, "postponed");
        seq_print_rq_state_bit(m, s & RQ_COMPLETION_SUSP, &sep, "suspended");
        sep = ' ';
        seq_print_rq_state_bit(m, s & RQ_LOCAL_PENDING, &sep, "pending");
        seq_print_rq_state_bit(m, s & RQ_LOCAL_COMPLETED, &sep, "completed");
        seq_print_rq_state_bit(m, s & RQ_LOCAL_ABORTED, &sep, "aborted");
        seq_print_rq_state_bit(m, s & RQ_LOCAL_OK, &sep, "ok");
        if (sep == ' ')
                seq_puts(m, " -");

        /* for_each_connection ... */
        seq_printf(m, "\tnet:");
        sep = ' ';
        seq_print_rq_state_bit(m, s & RQ_NET_PENDING, &sep, "pending");
        seq_print_rq_state_bit(m, s & RQ_NET_QUEUED, &sep, "queued");
        seq_print_rq_state_bit(m, s & RQ_NET_SENT, &sep, "sent");
        seq_print_rq_state_bit(m, s & RQ_NET_DONE, &sep, "done");
        seq_print_rq_state_bit(m, s & RQ_NET_SIS, &sep, "sis");
        seq_print_rq_state_bit(m, s & RQ_NET_OK, &sep, "ok");
        if (sep == ' ')
                seq_puts(m, " -");

        seq_printf(m, " :");
        sep = ' ';
        seq_print_rq_state_bit(m, s & RQ_EXP_RECEIVE_ACK, &sep, "B");
        seq_print_rq_state_bit(m, s & RQ_EXP_WRITE_ACK, &sep, "C");
        seq_print_rq_state_bit(m, s & RQ_EXP_BARR_ACK, &sep, "barr");
        if (sep == ' ')
                seq_puts(m, " -");
        seq_printf(m, "\n");
}

static void seq_print_one_request(struct seq_file *m, struct drbd_request *req, unsigned long now)
{
        /* change anything here, fixup header below! */
        unsigned int s = req->rq_state;

#define RQ_HDR_1 "epoch\tsector\tsize\trw"
        seq_printf(m, "0x%x\t%llu\t%u\t%s",
                req->epoch,
                (unsigned long long)req->i.sector, req->i.size >> 9,
                (s & RQ_WRITE) ? "W" : "R");

#define RQ_HDR_2 "\tstart\tin AL\tsubmit"
        seq_printf(m, "\t%d", jiffies_to_msecs(now - req->start_jif));
        seq_print_age_or_dash(m, s & RQ_IN_ACT_LOG, now - req->in_actlog_jif);
        seq_print_age_or_dash(m, s & RQ_LOCAL_PENDING, now - req->pre_submit_jif);

#define RQ_HDR_3 "\tsent\tacked\tdone"
        seq_print_age_or_dash(m, s & RQ_NET_SENT, now - req->pre_send_jif);
        seq_print_age_or_dash(m, (s & RQ_NET_SENT) && !(s & RQ_NET_PENDING), now - req->acked_jif);
        seq_print_age_or_dash(m, s & RQ_NET_DONE, now - req->net_done_jif);

#define RQ_HDR_4 "\tstate\n"
        seq_print_request_state(m, req);
}
#define RQ_HDR RQ_HDR_1 RQ_HDR_2 RQ_HDR_3 RQ_HDR_4

static void seq_print_minor_vnr_req(struct seq_file *m, struct drbd_request *req, unsigned long now)
{
        seq_printf(m, "%u\t%u\t", req->device->minor, req->device->vnr);
        seq_print_one_request(m, req, now);
}

static void seq_print_resource_pending_meta_io(struct seq_file *m, struct drbd_resource *resource, unsigned long now)
{
        struct drbd_device *device;
        unsigned int i;

        seq_puts(m, "minor\tvnr\tstart\tsubmit\tintent\n");
        rcu_read_lock();
        idr_for_each_entry(&resource->devices, device, i) {
                struct drbd_md_io tmp;
                /* In theory this is racy,
                 * in the sense that there could have been a
                 * drbd_md_put_buffer(); drbd_md_get_buffer();
                 * between accessing these members here.  */
                tmp = device->md_io;
                if (atomic_read(&tmp.in_use)) {
                        seq_printf(m, "%u\t%u\t%d\t",
                                device->minor, device->vnr,
                                jiffies_to_msecs(now - tmp.start_jif));
                        if (time_before(tmp.submit_jif, tmp.start_jif))
                                seq_puts(m, "-\t");
                        else
                                seq_printf(m, "%d\t", jiffies_to_msecs(now - tmp.submit_jif));
                        seq_printf(m, "%s\n", tmp.current_use);
                }
        }
        rcu_read_unlock();
}

static void seq_print_waiting_for_AL(struct seq_file *m, struct drbd_resource *resource, unsigned long now)
{
        struct drbd_device *device;
        unsigned int i;

        seq_puts(m, "minor\tvnr\tage\t#waiting\n");
        rcu_read_lock();
        idr_for_each_entry(&resource->devices, device, i) {
                unsigned long jif;
                struct drbd_request *req;
                int n = atomic_read(&device->ap_actlog_cnt);
                if (n) {
                        spin_lock_irq(&device->resource->req_lock);
                        req = list_first_entry_or_null(&device->pending_master_completion[1],
                                struct drbd_request, req_pending_master_completion);
                        /* if the oldest request does not wait for the activity log
                         * it is not interesting for us here */
                        if (req && !(req->rq_state & RQ_IN_ACT_LOG))
                                jif = req->start_jif;
                        else
                                req = NULL;
                        spin_unlock_irq(&device->resource->req_lock);
                }
                if (n) {
                        seq_printf(m, "%u\t%u\t", device->minor, device->vnr);
                        if (req)
                                seq_printf(m, "%u\t", jiffies_to_msecs(now - jif));
                        else
                                seq_puts(m, "-\t");
                        seq_printf(m, "%u\n", n);
                }
        }
        rcu_read_unlock();
}

static void seq_print_device_bitmap_io(struct seq_file *m, struct drbd_device *device, unsigned long now)
{
        struct drbd_bm_aio_ctx *ctx;
        unsigned long start_jif;
        unsigned int in_flight;
        unsigned int flags;
        spin_lock_irq(&device->resource->req_lock);
        ctx = list_first_entry_or_null(&device->pending_bitmap_io, struct drbd_bm_aio_ctx, list);
        if (ctx && ctx->done)
                ctx = NULL;
        if (ctx) {
                start_jif = ctx->start_jif;
                in_flight = atomic_read(&ctx->in_flight);
                flags = ctx->flags;
        }
        spin_unlock_irq(&device->resource->req_lock);
        if (ctx) {
                seq_printf(m, "%u\t%u\t%c\t%u\t%u\n",
                        device->minor, device->vnr,
                        (flags & BM_AIO_READ) ? 'R' : 'W',
                        jiffies_to_msecs(now - start_jif),
                        in_flight);
        }
}

static void seq_print_resource_pending_bitmap_io(struct seq_file *m, struct drbd_resource *resource, unsigned long now)
{
        struct drbd_device *device;
        unsigned int i;

        seq_puts(m, "minor\tvnr\trw\tage\t#in-flight\n");
        rcu_read_lock();
        idr_for_each_entry(&resource->devices, device, i) {
                seq_print_device_bitmap_io(m, device, now);
        }
        rcu_read_unlock();
}

/* pretty print enum peer_req->flags */
static void seq_print_peer_request_flags(struct seq_file *m, struct drbd_peer_request *peer_req)
{
        unsigned long f = peer_req->flags;
        char sep = ' ';

        __seq_print_rq_state_bit(m, f & EE_SUBMITTED, &sep, "submitted", "preparing");
        __seq_print_rq_state_bit(m, f & EE_APPLICATION, &sep, "application", "internal");
        seq_print_rq_state_bit(m, f & EE_CALL_AL_COMPLETE_IO, &sep, "in-AL");
        seq_print_rq_state_bit(m, f & EE_SEND_WRITE_ACK, &sep, "C");
        seq_print_rq_state_bit(m, f & EE_MAY_SET_IN_SYNC, &sep, "set-in-sync");

        if (f & EE_IS_TRIM) {
                seq_putc(m, sep);
                sep = '|';
                if (f & EE_IS_TRIM_USE_ZEROOUT)
                        seq_puts(m, "zero-out");
                else
                        seq_puts(m, "trim");
        }
        seq_putc(m, '\n');
}

static void seq_print_peer_request(struct seq_file *m,
        struct drbd_device *device, struct list_head *lh,
        unsigned long now)
{
        bool reported_preparing = false;
        struct drbd_peer_request *peer_req;
        list_for_each_entry(peer_req, lh, w.list) {
                if (reported_preparing && !(peer_req->flags & EE_SUBMITTED))
                        continue;

                if (device)
                        seq_printf(m, "%u\t%u\t", device->minor, device->vnr);

                seq_printf(m, "%llu\t%u\t%c\t%u\t",
                        (unsigned long long)peer_req->i.sector, peer_req->i.size >> 9,
                        (peer_req->flags & EE_WRITE) ? 'W' : 'R',
                        jiffies_to_msecs(now - peer_req->submit_jif));
                seq_print_peer_request_flags(m, peer_req);
                if (peer_req->flags & EE_SUBMITTED)
                        break;
                else
                        reported_preparing = true;
        }
}

static void seq_print_device_peer_requests(struct seq_file *m,
        struct drbd_device *device, unsigned long now)
{
        seq_puts(m, "minor\tvnr\tsector\tsize\trw\tage\tflags\n");
        spin_lock_irq(&device->resource->req_lock);
        seq_print_peer_request(m, device, &device->active_ee, now);
        seq_print_peer_request(m, device, &device->read_ee, now);
        seq_print_peer_request(m, device, &device->sync_ee, now);
        spin_unlock_irq(&device->resource->req_lock);
        if (test_bit(FLUSH_PENDING, &device->flags)) {
                seq_printf(m, "%u\t%u\t-\t-\tF\t%u\tflush\n",
                        device->minor, device->vnr,
                        jiffies_to_msecs(now - device->flush_jif));
        }
}

static void seq_print_resource_pending_peer_requests(struct seq_file *m,
        struct drbd_resource *resource, unsigned long now)
{
        struct drbd_device *device;
        unsigned int i;

        rcu_read_lock();
        idr_for_each_entry(&resource->devices, device, i) {
                seq_print_device_peer_requests(m, device, now);
        }
        rcu_read_unlock();
}

static void seq_print_resource_transfer_log_summary(struct seq_file *m,
        struct drbd_resource *resource,
        struct drbd_connection *connection,
        unsigned long now)
{
        struct drbd_request *req;
        unsigned int count = 0;
        unsigned int show_state = 0;

        seq_puts(m, "n\tdevice\tvnr\t" RQ_HDR);
        spin_lock_irq(&resource->req_lock);
        list_for_each_entry(req, &connection->transfer_log, tl_requests) {
                unsigned int tmp = 0;
                unsigned int s;
                ++count;

                /* don't disable irq "forever" */
                if (!(count & 0x1ff)) {
                        struct drbd_request *req_next;
                        kref_get(&req->kref);
                        spin_unlock_irq(&resource->req_lock);
                        cond_resched();
                        spin_lock_irq(&resource->req_lock);
                        req_next = list_next_entry(req, tl_requests);
                        if (kref_put(&req->kref, drbd_req_destroy))
                                req = req_next;
                        if (&req->tl_requests == &connection->transfer_log)
                                break;
                }

                s = req->rq_state;

                /* This is meant to summarize timing issues, to be able to tell
                 * local disk problems from network problems.
                 * Skip requests, if we have shown an even older request with
                 * similar aspects already.  */
                if (req->master_bio == NULL)
                        tmp |= 1;
                if ((s & RQ_LOCAL_MASK) && (s & RQ_LOCAL_PENDING))
                        tmp |= 2;
                if (s & RQ_NET_MASK) {
                        if (!(s & RQ_NET_SENT))
                                tmp |= 4;
                        if (s & RQ_NET_PENDING)
                                tmp |= 8;
                        if (!(s & RQ_NET_DONE))
                                tmp |= 16;
                }
                if ((tmp & show_state) == tmp)
                        continue;
                show_state |= tmp;
                seq_printf(m, "%u\t", count);
                seq_print_minor_vnr_req(m, req, now);
                if (show_state == 0x1f)
                        break;
        }
        spin_unlock_irq(&resource->req_lock);
}

/* TODO: transfer_log and friends should be moved to resource */
static int in_flight_summary_show(struct seq_file *m, void *pos)
{
        struct drbd_resource *resource = m->private;
        struct drbd_connection *connection;
        unsigned long jif = jiffies;

        connection = first_connection(resource);
        /* This does not happen, actually.
         * But be robust and prepare for future code changes. */
        if (!connection || !kref_get_unless_zero(&connection->kref))
                return -ESTALE;

        /* BUMP me if you change the file format/content/presentation */
        seq_printf(m, "v: %u\n\n", 0);

        seq_puts(m, "oldest bitmap IO\n");
        seq_print_resource_pending_bitmap_io(m, resource, jif);
        seq_putc(m, '\n');

        seq_puts(m, "meta data IO\n");
        seq_print_resource_pending_meta_io(m, resource, jif);
        seq_putc(m, '\n');

        seq_puts(m, "socket buffer stats\n");
        /* for each connection ... once we have more than one */
        rcu_read_lock();
        if (connection->data.socket) {
                /* open coded SIOCINQ, the "relevant" part */
                struct tcp_sock *tp = tcp_sk(connection->data.socket->sk);
                int answ = tp->rcv_nxt - tp->copied_seq;
                seq_printf(m, "unread receive buffer: %u Byte\n", answ);
                /* open coded SIOCOUTQ, the "relevant" part */
                answ = tp->write_seq - tp->snd_una;
                seq_printf(m, "unacked send buffer: %u Byte\n", answ);
        }
        rcu_read_unlock();
        seq_putc(m, '\n');

        seq_puts(m, "oldest peer requests\n");
        seq_print_resource_pending_peer_requests(m, resource, jif);
        seq_putc(m, '\n');

        seq_puts(m, "application requests waiting for activity log\n");
        seq_print_waiting_for_AL(m, resource, jif);
        seq_putc(m, '\n');

        seq_puts(m, "oldest application requests\n");
        seq_print_resource_transfer_log_summary(m, resource, connection, jif);
        seq_putc(m, '\n');

        jif = jiffies - jif;
        if (jif)
                seq_printf(m, "generated in %d ms\n", jiffies_to_msecs(jif));
        kref_put(&connection->kref, drbd_destroy_connection);
        return 0;
}

/* simple_positive(file->f_path.dentry) respectively debugfs_positive(),
 * but neither is "reachable" from here.
 * So we have our own inline version of it above.  :-( */
static inline int debugfs_positive(struct dentry *dentry)
{
        return dentry->d_inode && !d_unhashed(dentry);
}

/* make sure at *open* time that the respective object won't go away. */
static int drbd_single_open(struct file *file, int (*show)(struct seq_file *, void *),
                                void *data, struct kref *kref,
                                void (*release)(struct kref *))
{
        struct dentry *parent;
        int ret = -ESTALE;

        /* Are we still linked,
         * or has debugfs_remove() already been called? */
        parent = file->f_path.dentry->d_parent;
        /* not sure if this can happen: */
        if (!parent || !parent->d_inode)
                goto out;
        /* serialize with d_delete() */
        mutex_lock(&parent->d_inode->i_mutex);
        /* Make sure the object is still alive */
        if (debugfs_positive(file->f_path.dentry)
        && kref_get_unless_zero(kref))
                ret = 0;
        mutex_unlock(&parent->d_inode->i_mutex);
        if (!ret) {
                ret = single_open(file, show, data);
                if (ret)
                        kref_put(kref, release);
        }
out:
        return ret;
}

static int in_flight_summary_open(struct inode *inode, struct file *file)
{
        struct drbd_resource *resource = inode->i_private;
        return drbd_single_open(file, in_flight_summary_show, resource,
                                &resource->kref, drbd_destroy_resource);
}

static int in_flight_summary_release(struct inode *inode, struct file *file)
{
        struct drbd_resource *resource = inode->i_private;
        kref_put(&resource->kref, drbd_destroy_resource);
        return single_release(inode, file);
}

static const struct file_operations in_flight_summary_fops = {
        .owner          = THIS_MODULE,
        .open           = in_flight_summary_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = in_flight_summary_release,
};

void drbd_debugfs_resource_add(struct drbd_resource *resource)
{
        struct dentry *dentry;
        if (!drbd_debugfs_resources)
                return;

        dentry = debugfs_create_dir(resource->name, drbd_debugfs_resources);
        if (IS_ERR_OR_NULL(dentry))
                goto fail;
        resource->debugfs_res = dentry;

        dentry = debugfs_create_dir("volumes", resource->debugfs_res);
        if (IS_ERR_OR_NULL(dentry))
                goto fail;
        resource->debugfs_res_volumes = dentry;

        dentry = debugfs_create_dir("connections", resource->debugfs_res);
        if (IS_ERR_OR_NULL(dentry))
                goto fail;
        resource->debugfs_res_connections = dentry;

        dentry = debugfs_create_file("in_flight_summary", S_IRUSR|S_IRGRP,
                        resource->debugfs_res, resource,
                        &in_flight_summary_fops);
        if (IS_ERR_OR_NULL(dentry))
                goto fail;
        resource->debugfs_res_in_flight_summary = dentry;
        return;

fail:
        drbd_debugfs_resource_cleanup(resource);
        drbd_err(resource, "failed to create debugfs dentry\n");
}

static void drbd_debugfs_remove(struct dentry **dp)
{
        debugfs_remove(*dp);
        *dp = NULL;
}

void drbd_debugfs_resource_cleanup(struct drbd_resource *resource)
{
        /* it is ok to call debugfs_remove(NULL) */
        drbd_debugfs_remove(&resource->debugfs_res_in_flight_summary);
        drbd_debugfs_remove(&resource->debugfs_res_connections);
        drbd_debugfs_remove(&resource->debugfs_res_volumes);
        drbd_debugfs_remove(&resource->debugfs_res);
}

static void seq_print_one_timing_detail(struct seq_file *m,
        const struct drbd_thread_timing_details *tdp,
        unsigned long now)
{
        struct drbd_thread_timing_details td;
        /* No locking...
         * use temporary assignment to get at consistent data. */
        do {
                td = *tdp;
        } while (td.cb_nr != tdp->cb_nr);
        if (!td.cb_addr)
                return;
        seq_printf(m, "%u\t%d\t%s:%u\t%ps\n",
                        td.cb_nr,
                        jiffies_to_msecs(now - td.start_jif),
                        td.caller_fn, td.line,
                        td.cb_addr);
}

static void seq_print_timing_details(struct seq_file *m,
                const char *title,
                unsigned int cb_nr, struct drbd_thread_timing_details *tdp, unsigned long now)
{
        unsigned int start_idx;
        unsigned int i;

        seq_printf(m, "%s\n", title);
        /* If not much is going on, this will result in natural ordering.
         * If it is very busy, we will possibly skip events, or even see wrap
         * arounds, which could only be avoided with locking.
         */
        start_idx = cb_nr % DRBD_THREAD_DETAILS_HIST;
        for (i = start_idx; i < DRBD_THREAD_DETAILS_HIST; i++)
                seq_print_one_timing_detail(m, tdp+i, now);
        for (i = 0; i < start_idx; i++)
                seq_print_one_timing_detail(m, tdp+i, now);
}

static int callback_history_show(struct seq_file *m, void *ignored)
{
        struct drbd_connection *connection = m->private;
        unsigned long jif = jiffies;

        /* BUMP me if you change the file format/content/presentation */
        seq_printf(m, "v: %u\n\n", 0);

        seq_puts(m, "n\tage\tcallsite\tfn\n");
        seq_print_timing_details(m, "worker", connection->w_cb_nr, connection->w_timing_details, jif);
        seq_print_timing_details(m, "receiver", connection->r_cb_nr, connection->r_timing_details, jif);
        return 0;
}

static int callback_history_open(struct inode *inode, struct file *file)
{
        struct drbd_connection *connection = inode->i_private;
        return drbd_single_open(file, callback_history_show, connection,
                                &connection->kref, drbd_destroy_connection);
}

static int callback_history_release(struct inode *inode, struct file *file)
{
        struct drbd_connection *connection = inode->i_private;
        kref_put(&connection->kref, drbd_destroy_connection);
        return single_release(inode, file);
}

static const struct file_operations connection_callback_history_fops = {
        .owner          = THIS_MODULE,
        .open           = callback_history_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = callback_history_release,
};

static int connection_oldest_requests_show(struct seq_file *m, void *ignored)
{
        struct drbd_connection *connection = m->private;
        unsigned long now = jiffies;
        struct drbd_request *r1, *r2;

        /* BUMP me if you change the file format/content/presentation */
        seq_printf(m, "v: %u\n\n", 0);

        spin_lock_irq(&connection->resource->req_lock);
        r1 = connection->req_next;
        if (r1)
                seq_print_minor_vnr_req(m, r1, now);
        r2 = connection->req_ack_pending;
        if (r2 && r2 != r1) {
                r1 = r2;
                seq_print_minor_vnr_req(m, r1, now);
        }
        r2 = connection->req_not_net_done;
        if (r2 && r2 != r1)
                seq_print_minor_vnr_req(m, r2, now);
        spin_unlock_irq(&connection->resource->req_lock);
        return 0;
}

static int connection_oldest_requests_open(struct inode *inode, struct file *file)
{
        struct drbd_connection *connection = inode->i_private;
        return drbd_single_open(file, connection_oldest_requests_show, connection,
                                &connection->kref, drbd_destroy_connection);
}

static int connection_oldest_requests_release(struct inode *inode, struct file *file)
{
        struct drbd_connection *connection = inode->i_private;
        kref_put(&connection->kref, drbd_destroy_connection);
        return single_release(inode, file);
}

static const struct file_operations connection_oldest_requests_fops = {
        .owner          = THIS_MODULE,
        .open           = connection_oldest_requests_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = connection_oldest_requests_release,
};

void drbd_debugfs_connection_add(struct drbd_connection *connection)
{
        struct dentry *conns_dir = connection->resource->debugfs_res_connections;
        struct dentry *dentry;
        if (!conns_dir)
                return;

        /* Once we enable mutliple peers,
         * these connections will have descriptive names.
         * For now, it is just the one connection to the (only) "peer". */
        dentry = debugfs_create_dir("peer", conns_dir);
        if (IS_ERR_OR_NULL(dentry))
                goto fail;
        connection->debugfs_conn = dentry;

        dentry = debugfs_create_file("callback_history", S_IRUSR|S_IRGRP,
                        connection->debugfs_conn, connection,
                        &connection_callback_history_fops);
        if (IS_ERR_OR_NULL(dentry))
                goto fail;
        connection->debugfs_conn_callback_history = dentry;

        dentry = debugfs_create_file("oldest_requests", S_IRUSR|S_IRGRP,
                        connection->debugfs_conn, connection,
                        &connection_oldest_requests_fops);
        if (IS_ERR_OR_NULL(dentry))
                goto fail;
        connection->debugfs_conn_oldest_requests = dentry;
        return;

fail:
        drbd_debugfs_connection_cleanup(connection);
        drbd_err(connection, "failed to create debugfs dentry\n");
}

void drbd_debugfs_connection_cleanup(struct drbd_connection *connection)
{
        drbd_debugfs_remove(&connection->debugfs_conn_callback_history);
        drbd_debugfs_remove(&connection->debugfs_conn_oldest_requests);
        drbd_debugfs_remove(&connection->debugfs_conn);
}

static void resync_dump_detail(struct seq_file *m, struct lc_element *e)
{
       struct bm_extent *bme = lc_entry(e, struct bm_extent, lce);

       seq_printf(m, "%5d %s %s %s", bme->rs_left,
                  test_bit(BME_NO_WRITES, &bme->flags) ? "NO_WRITES" : "---------",
                  test_bit(BME_LOCKED, &bme->flags) ? "LOCKED" : "------",
                  test_bit(BME_PRIORITY, &bme->flags) ? "PRIORITY" : "--------"
                  );
}

static int device_resync_extents_show(struct seq_file *m, void *ignored)
{
        struct drbd_device *device = m->private;

        /* BUMP me if you change the file format/content/presentation */
        seq_printf(m, "v: %u\n\n", 0);

        if (get_ldev_if_state(device, D_FAILED)) {
                lc_seq_printf_stats(m, device->resync);
                lc_seq_dump_details(m, device->resync, "rs_left flags", resync_dump_detail);
                put_ldev(device);
        }
        return 0;
}

static int device_act_log_extents_show(struct seq_file *m, void *ignored)
{
        struct drbd_device *device = m->private;

        /* BUMP me if you change the file format/content/presentation */
        seq_printf(m, "v: %u\n\n", 0);

        if (get_ldev_if_state(device, D_FAILED)) {
                lc_seq_printf_stats(m, device->act_log);
                lc_seq_dump_details(m, device->act_log, "", NULL);
                put_ldev(device);
        }
        return 0;
}

static int device_oldest_requests_show(struct seq_file *m, void *ignored)
{
        struct drbd_device *device = m->private;
        struct drbd_resource *resource = device->resource;
        unsigned long now = jiffies;
        struct drbd_request *r1, *r2;
        int i;

        /* BUMP me if you change the file format/content/presentation */
        seq_printf(m, "v: %u\n\n", 0);

        seq_puts(m, RQ_HDR);
        spin_lock_irq(&resource->req_lock);
        /* WRITE, then READ */
        for (i = 1; i >= 0; --i) {
                r1 = list_first_entry_or_null(&device->pending_master_completion[i],
                        struct drbd_request, req_pending_master_completion);
                r2 = list_first_entry_or_null(&device->pending_completion[i],
                        struct drbd_request, req_pending_local);
                if (r1)
                        seq_print_one_request(m, r1, now);
                if (r2 && r2 != r1)
                        seq_print_one_request(m, r2, now);
        }
        spin_unlock_irq(&resource->req_lock);
        return 0;
}

static int device_data_gen_id_show(struct seq_file *m, void *ignored)
{
        struct drbd_device *device = m->private;
        struct drbd_md *md;
        enum drbd_uuid_index idx;

        if (!get_ldev_if_state(device, D_FAILED))
                return -ENODEV;

        md = &device->ldev->md;
        spin_lock_irq(&md->uuid_lock);
        for (idx = UI_CURRENT; idx <= UI_HISTORY_END; idx++) {
                seq_printf(m, "0x%016llX\n", md->uuid[idx]);
        }
        spin_unlock_irq(&md->uuid_lock);
        put_ldev(device);
        return 0;
}

#define drbd_debugfs_device_attr(name)                                          \
static int device_ ## name ## _open(struct inode *inode, struct file *file)     \
{                                                                               \
        struct drbd_device *device = inode->i_private;                          \
        return drbd_single_open(file, device_ ## name ## _show, device,         \
                                &device->kref, drbd_destroy_device);            \
}                                                                               \
static int device_ ## name ## _release(struct inode *inode, struct file *file)  \
{                                                                               \
        struct drbd_device *device = inode->i_private;                          \
        kref_put(&device->kref, drbd_destroy_device);                           \
        return single_release(inode, file);                                     \
}                                                                               \
static const struct file_operations device_ ## name ## _fops = {                \
        .owner          = THIS_MODULE,                                          \
        .open           = device_ ## name ## _open,                             \
        .read           = seq_read,                                             \
        .llseek         = seq_lseek,                                            \
        .release        = device_ ## name ## _release,                          \
};

drbd_debugfs_device_attr(oldest_requests)
drbd_debugfs_device_attr(act_log_extents)
drbd_debugfs_device_attr(resync_extents)
drbd_debugfs_device_attr(data_gen_id)

void drbd_debugfs_device_add(struct drbd_device *device)
{
        struct dentry *vols_dir = device->resource->debugfs_res_volumes;
        char minor_buf[8]; /* MINORMASK, MINORBITS == 20; */
        char vnr_buf[8];   /* volume number vnr is even 16 bit only; */
        char *slink_name = NULL;

        struct dentry *dentry;
        if (!vols_dir || !drbd_debugfs_minors)
                return;

        snprintf(vnr_buf, sizeof(vnr_buf), "%u", device->vnr);
        dentry = debugfs_create_dir(vnr_buf, vols_dir);
        if (IS_ERR_OR_NULL(dentry))
                goto fail;
        device->debugfs_vol = dentry;

        snprintf(minor_buf, sizeof(minor_buf), "%u", device->minor);
        slink_name = kasprintf(GFP_KERNEL, "../resources/%s/volumes/%u",
                        device->resource->name, device->vnr);
        if (!slink_name)
                goto fail;
        dentry = debugfs_create_symlink(minor_buf, drbd_debugfs_minors, slink_name);
        kfree(slink_name);
        slink_name = NULL;
        if (IS_ERR_OR_NULL(dentry))
                goto fail;
        device->debugfs_minor = dentry;

#define DCF(name)       do {                                    \
        dentry = debugfs_create_file(#name, S_IRUSR|S_IRGRP,    \
                        device->debugfs_vol, device,            \
                        &device_ ## name ## _fops);             \
        if (IS_ERR_OR_NULL(dentry))                             \
                goto fail;                                      \
        device->debugfs_vol_ ## name = dentry;                  \
        } while (0)

        DCF(oldest_requests);
        DCF(act_log_extents);
        DCF(resync_extents);
        DCF(data_gen_id);
#undef DCF
        return;

fail:
        drbd_debugfs_device_cleanup(device);
        drbd_err(device, "failed to create debugfs entries\n");
}

void drbd_debugfs_device_cleanup(struct drbd_device *device)
{
        drbd_debugfs_remove(&device->debugfs_minor);
        drbd_debugfs_remove(&device->debugfs_vol_oldest_requests);
        drbd_debugfs_remove(&device->debugfs_vol_act_log_extents);
        drbd_debugfs_remove(&device->debugfs_vol_resync_extents);
        drbd_debugfs_remove(&device->debugfs_vol_data_gen_id);
        drbd_debugfs_remove(&device->debugfs_vol);
}

void drbd_debugfs_peer_device_add(struct drbd_peer_device *peer_device)
{
        struct dentry *conn_dir = peer_device->connection->debugfs_conn;
        struct dentry *dentry;
        char vnr_buf[8];

        if (!conn_dir)
                return;

        snprintf(vnr_buf, sizeof(vnr_buf), "%u", peer_device->device->vnr);
        dentry = debugfs_create_dir(vnr_buf, conn_dir);
        if (IS_ERR_OR_NULL(dentry))
                goto fail;
        peer_device->debugfs_peer_dev = dentry;
        return;

fail:
        drbd_debugfs_peer_device_cleanup(peer_device);
        drbd_err(peer_device, "failed to create debugfs entries\n");
}

void drbd_debugfs_peer_device_cleanup(struct drbd_peer_device *peer_device)
{
        drbd_debugfs_remove(&peer_device->debugfs_peer_dev);
}

static int drbd_version_show(struct seq_file *m, void *ignored)
{
        seq_printf(m, "# %s\n", drbd_buildtag());
        seq_printf(m, "VERSION=%s\n", REL_VERSION);
        seq_printf(m, "API_VERSION=%u\n", API_VERSION);
        seq_printf(m, "PRO_VERSION_MIN=%u\n", PRO_VERSION_MIN);
        seq_printf(m, "PRO_VERSION_MAX=%u\n", PRO_VERSION_MAX);
        return 0;
}

static int drbd_version_open(struct inode *inode, struct file *file)
{
        return single_open(file, drbd_version_show, NULL);
}

static struct file_operations drbd_version_fops = {
        .owner = THIS_MODULE,
        .open = drbd_version_open,
        .llseek = seq_lseek,
        .read = seq_read,
        .release = single_release,
};

/* not __exit, may be indirectly called
 * from the module-load-failure path as well. */
void drbd_debugfs_cleanup(void)
{
        drbd_debugfs_remove(&drbd_debugfs_resources);
        drbd_debugfs_remove(&drbd_debugfs_minors);
        drbd_debugfs_remove(&drbd_debugfs_version);
        drbd_debugfs_remove(&drbd_debugfs_root);
}

int __init drbd_debugfs_init(void)
{
        struct dentry *dentry;

        dentry = debugfs_create_dir("drbd", NULL);
        if (IS_ERR_OR_NULL(dentry))
                goto fail;
        drbd_debugfs_root = dentry;

        dentry = debugfs_create_file("version", 0444, drbd_debugfs_root, NULL, &drbd_version_fops);
        if (IS_ERR_OR_NULL(dentry))
                goto fail;
        drbd_debugfs_version = dentry;

        dentry = debugfs_create_dir("resources", drbd_debugfs_root);
        if (IS_ERR_OR_NULL(dentry))
                goto fail;
        drbd_debugfs_resources = dentry;

        dentry = debugfs_create_dir("minors", drbd_debugfs_root);
        if (IS_ERR_OR_NULL(dentry))
                goto fail;
        drbd_debugfs_minors = dentry;
        return 0;

fail:
        drbd_debugfs_cleanup();
        if (dentry)
                return PTR_ERR(dentry);
        else
                return -EINVAL;
}