// SPDX-License-Identifier: GPL-2.0
/*
 * quota.c - CephFS quota
 *
 * Copyright (C) 2017-2018 SUSE
 */

#include <linux/statfs.h>

#include "super.h"
#include "mds_client.h"

void ceph_adjust_quota_realms_count(struct inode *inode, bool inc)
{
        struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;
        if (inc)
                atomic64_inc(&mdsc->quotarealms_count);
        else
                atomic64_dec(&mdsc->quotarealms_count);
}

static inline bool ceph_has_realms_with_quotas(struct inode *inode)
{
        struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;
        struct super_block *sb = mdsc->fsc->sb;

        if (atomic64_read(&mdsc->quotarealms_count) > 0)
                return true;
        /* if root is the real CephFS root, we don't have quota realms */
        if (sb->s_root->d_inode &&
            (sb->s_root->d_inode->i_ino == CEPH_INO_ROOT))
                return false;
        /* otherwise, we can't know for sure */
        return true;
}

void ceph_handle_quota(struct ceph_mds_client *mdsc,
                       struct ceph_mds_session *session,
                       struct ceph_msg *msg)
{
        struct super_block *sb = mdsc->fsc->sb;
        struct ceph_mds_quota *h = msg->front.iov_base;
        struct ceph_vino vino;
        struct inode *inode;
        struct ceph_inode_info *ci;

        if (msg->front.iov_len < sizeof(*h)) {
                pr_err("%s corrupt message mds%d len %d\n", __func__,
                       session->s_mds, (int)msg->front.iov_len);
                ceph_msg_dump(msg);
                return;
        }

        /* increment msg sequence number */
        mutex_lock(&session->s_mutex);
        session->s_seq++;
        mutex_unlock(&session->s_mutex);

        /* lookup inode */
        vino.ino = le64_to_cpu(h->ino);
        vino.snap = CEPH_NOSNAP;
        inode = ceph_find_inode(sb, vino);
        if (!inode) {
                pr_warn("Failed to find inode %llu\n", vino.ino);
                return;
        }
        ci = ceph_inode(inode);

        spin_lock(&ci->i_ceph_lock);
        ci->i_rbytes = le64_to_cpu(h->rbytes);
        ci->i_rfiles = le64_to_cpu(h->rfiles);
        ci->i_rsubdirs = le64_to_cpu(h->rsubdirs);
        __ceph_update_quota(ci, le64_to_cpu(h->max_bytes),
                            le64_to_cpu(h->max_files));
        spin_unlock(&ci->i_ceph_lock);

        /* avoid calling iput_final() in dispatch thread */
        ceph_async_iput(inode);
}

static struct ceph_quotarealm_inode *
find_quotarealm_inode(struct ceph_mds_client *mdsc, u64 ino)
{
        struct ceph_quotarealm_inode *qri = NULL;
        struct rb_node **node, *parent = NULL;

        mutex_lock(&mdsc->quotarealms_inodes_mutex);
        node = &(mdsc->quotarealms_inodes.rb_node);
        while (*node) {
                parent = *node;
                qri = container_of(*node, struct ceph_quotarealm_inode, node);

                if (ino < qri->ino)
                        node = &((*node)->rb_left);
                else if (ino > qri->ino)
                        node = &((*node)->rb_right);
                else
                        break;
        }
        if (!qri || (qri->ino != ino)) {
                /* Not found, create a new one and insert it */
                qri = kmalloc(sizeof(*qri), GFP_KERNEL);
                if (qri) {
                        qri->ino = ino;
                        qri->inode = NULL;
                        qri->timeout = 0;
                        mutex_init(&qri->mutex);
                        rb_link_node(&qri->node, parent, node);
                        rb_insert_color(&qri->node, &mdsc->quotarealms_inodes);
                } else
                        pr_warn("Failed to alloc quotarealms_inode\n");
        }
        mutex_unlock(&mdsc->quotarealms_inodes_mutex);

        return qri;
}

/*
 * This function will try to lookup a realm inode which isn't visible in the
 * filesystem mountpoint.  A list of these kind of inodes (not visible) is
 * maintained in the mdsc and freed only when the filesystem is umounted.
 *
 * Note that these inodes are kept in this list even if the lookup fails, which
 * allows to prevent useless lookup requests.
 */
static struct inode *lookup_quotarealm_inode(struct ceph_mds_client *mdsc,
                                             struct super_block *sb,
                                             struct ceph_snap_realm *realm)
{
        struct ceph_quotarealm_inode *qri;
        struct inode *in;

        qri = find_quotarealm_inode(mdsc, realm->ino);
        if (!qri)
                return NULL;

        mutex_lock(&qri->mutex);
        if (qri->inode) {
                /* A request has already returned the inode */
                mutex_unlock(&qri->mutex);
                return qri->inode;
        }
        /* Check if this inode lookup has failed recently */
        if (qri->timeout &&
            time_before_eq(jiffies, qri->timeout)) {
                mutex_unlock(&qri->mutex);
                return NULL;
        }
        in = ceph_lookup_inode(sb, realm->ino);
        if (IS_ERR(in)) {
                pr_warn("Can't lookup inode %llx (err: %ld)\n",
                        realm->ino, PTR_ERR(in));
                qri->timeout = jiffies + msecs_to_jiffies(60 * 1000); /* XXX */
        } else {
                qri->timeout = 0;
                qri->inode = in;
        }
        mutex_unlock(&qri->mutex);

        return in;
}

void ceph_cleanup_quotarealms_inodes(struct ceph_mds_client *mdsc)
{
        struct ceph_quotarealm_inode *qri;
        struct rb_node *node;

        /*
         * It should now be safe to clean quotarealms_inode tree without holding
         * mdsc->quotarealms_inodes_mutex...
         */
        mutex_lock(&mdsc->quotarealms_inodes_mutex);
        while (!RB_EMPTY_ROOT(&mdsc->quotarealms_inodes)) {
                node = rb_first(&mdsc->quotarealms_inodes);
                qri = rb_entry(node, struct ceph_quotarealm_inode, node);
                rb_erase(node, &mdsc->quotarealms_inodes);
                iput(qri->inode);
                kfree(qri);
        }
        mutex_unlock(&mdsc->quotarealms_inodes_mutex);
}

/*
 * This function walks through the snaprealm for an inode and returns the
 * ceph_snap_realm for the first snaprealm that has quotas set (either max_files
 * or max_bytes).  If the root is reached, return the root ceph_snap_realm
 * instead.
 *
 * Note that the caller is responsible for calling ceph_put_snap_realm() on the
 * returned realm.
 *
 * Callers of this function need to hold mdsc->snap_rwsem.  However, if there's
 * a need to do an inode lookup, this rwsem will be temporarily dropped.  Hence
 * the 'retry' argument: if rwsem needs to be dropped and 'retry' is 'false'
 * this function will return -EAGAIN; otherwise, the snaprealms walk-through
 * will be restarted.
 */
static struct ceph_snap_realm *get_quota_realm(struct ceph_mds_client *mdsc,
                                               struct inode *inode, bool retry)
{
        struct ceph_inode_info *ci = NULL;
        struct ceph_snap_realm *realm, *next;
        struct inode *in;
        bool has_quota;

        if (ceph_snap(inode) != CEPH_NOSNAP)
                return NULL;

restart:
        realm = ceph_inode(inode)->i_snap_realm;
        if (realm)
                ceph_get_snap_realm(mdsc, realm);
        else
                pr_err_ratelimited("get_quota_realm: ino (%llx.%llx) "
                                   "null i_snap_realm\n", ceph_vinop(inode));
        while (realm) {
                bool has_inode;

                spin_lock(&realm->inodes_with_caps_lock);
                has_inode = realm->inode;
                in = has_inode ? igrab(realm->inode) : NULL;
                spin_unlock(&realm->inodes_with_caps_lock);
                if (has_inode && !in)
                        break;
                if (!in) {
                        up_read(&mdsc->snap_rwsem);
                        in = lookup_quotarealm_inode(mdsc, inode->i_sb, realm);
                        down_read(&mdsc->snap_rwsem);
                        if (IS_ERR_OR_NULL(in))
                                break;
                        ceph_put_snap_realm(mdsc, realm);
                        if (!retry)
                                return ERR_PTR(-EAGAIN);
                        goto restart;
                }

                ci = ceph_inode(in);
                has_quota = __ceph_has_any_quota(ci);
                /* avoid calling iput_final() while holding mdsc->snap_rwsem */
                ceph_async_iput(in);

                next = realm->parent;
                if (has_quota || !next)
                       return realm;

                ceph_get_snap_realm(mdsc, next);
                ceph_put_snap_realm(mdsc, realm);
                realm = next;
        }
        if (realm)
                ceph_put_snap_realm(mdsc, realm);

        return NULL;
}

bool ceph_quota_is_same_realm(struct inode *old, struct inode *new)
{
        struct ceph_mds_client *mdsc = ceph_inode_to_client(old)->mdsc;
        struct ceph_snap_realm *old_realm, *new_realm;
        bool is_same;

restart:
        /*
         * We need to lookup 2 quota realms atomically, i.e. with snap_rwsem.
         * However, get_quota_realm may drop it temporarily.  By setting the
         * 'retry' parameter to 'false', we'll get -EAGAIN if the rwsem was
         * dropped and we can then restart the whole operation.
         */
        down_read(&mdsc->snap_rwsem);
        old_realm = get_quota_realm(mdsc, old, true);
        new_realm = get_quota_realm(mdsc, new, false);
        if (PTR_ERR(new_realm) == -EAGAIN) {
                up_read(&mdsc->snap_rwsem);
                if (old_realm)
                        ceph_put_snap_realm(mdsc, old_realm);
                goto restart;
        }
        is_same = (old_realm == new_realm);
        up_read(&mdsc->snap_rwsem);

        if (old_realm)
                ceph_put_snap_realm(mdsc, old_realm);
        if (new_realm)
                ceph_put_snap_realm(mdsc, new_realm);

        return is_same;
}

enum quota_check_op {
        QUOTA_CHECK_MAX_FILES_OP,       /* check quota max_files limit */
        QUOTA_CHECK_MAX_BYTES_OP,       /* check quota max_files limit */
        QUOTA_CHECK_MAX_BYTES_APPROACHING_OP    /* check if quota max_files
                                                   limit is approaching */
};

/*
 * check_quota_exceeded() will walk up the snaprealm hierarchy and, for each
 * realm, it will execute quota check operation defined by the 'op' parameter.
 * The snaprealm walk is interrupted if the quota check detects that the quota
 * is exceeded or if the root inode is reached.
 */
static bool check_quota_exceeded(struct inode *inode, enum quota_check_op op,
                                 loff_t delta)
{
        struct ceph_mds_client *mdsc = ceph_inode_to_client(inode)->mdsc;
        struct ceph_inode_info *ci;
        struct ceph_snap_realm *realm, *next;
        struct inode *in;
        u64 max, rvalue;
        bool exceeded = false;

        if (ceph_snap(inode) != CEPH_NOSNAP)
                return false;

        down_read(&mdsc->snap_rwsem);
restart:
        realm = ceph_inode(inode)->i_snap_realm;
        if (realm)
                ceph_get_snap_realm(mdsc, realm);
        else
                pr_err_ratelimited("check_quota_exceeded: ino (%llx.%llx) "
                                   "null i_snap_realm\n", ceph_vinop(inode));
        while (realm) {
                bool has_inode;

                spin_lock(&realm->inodes_with_caps_lock);
                has_inode = realm->inode;
                in = has_inode ? igrab(realm->inode) : NULL;
                spin_unlock(&realm->inodes_with_caps_lock);
                if (has_inode && !in)
                        break;
                if (!in) {
                        up_read(&mdsc->snap_rwsem);
                        in = lookup_quotarealm_inode(mdsc, inode->i_sb, realm);
                        down_read(&mdsc->snap_rwsem);
                        if (IS_ERR_OR_NULL(in))
                                break;
                        ceph_put_snap_realm(mdsc, realm);
                        goto restart;
                }
                ci = ceph_inode(in);
                spin_lock(&ci->i_ceph_lock);
                if (op == QUOTA_CHECK_MAX_FILES_OP) {
                        max = ci->i_max_files;
                        rvalue = ci->i_rfiles + ci->i_rsubdirs;
                } else {
                        max = ci->i_max_bytes;
                        rvalue = ci->i_rbytes;
                }
                spin_unlock(&ci->i_ceph_lock);
                switch (op) {
                case QUOTA_CHECK_MAX_FILES_OP:
                        exceeded = (max && (rvalue >= max));
                        break;
                case QUOTA_CHECK_MAX_BYTES_OP:
                        exceeded = (max && (rvalue + delta > max));
                        break;
                case QUOTA_CHECK_MAX_BYTES_APPROACHING_OP:
                        if (max) {
                                if (rvalue >= max)
                                        exceeded = true;
                                else {
                                        /*
                                         * when we're writing more that 1/16th
                                         * of the available space
                                         */
                                        exceeded =
                                                (((max - rvalue) >> 4) < delta);
                                }
                        }
                        break;
                default:
                        /* Shouldn't happen */
                        pr_warn("Invalid quota check op (%d)\n", op);
                        exceeded = true; /* Just break the loop */
                }
                /* avoid calling iput_final() while holding mdsc->snap_rwsem */
                ceph_async_iput(in);

                next = realm->parent;
                if (exceeded || !next)
                        break;
                ceph_get_snap_realm(mdsc, next);
                ceph_put_snap_realm(mdsc, realm);
                realm = next;
        }
        if (realm)
                ceph_put_snap_realm(mdsc, realm);
        up_read(&mdsc->snap_rwsem);

        return exceeded;
}

/*
 * ceph_quota_is_max_files_exceeded - check if we can create a new file
 * @inode:      directory where a new file is being created
 *
 * This functions returns true is max_files quota allows a new file to be
 * created.  It is necessary to walk through the snaprealm hierarchy (until the
 * FS root) to check all realms with quotas set.
 */
bool ceph_quota_is_max_files_exceeded(struct inode *inode)
{
        if (!ceph_has_realms_with_quotas(inode))
                return false;

        WARN_ON(!S_ISDIR(inode->i_mode));

        return check_quota_exceeded(inode, QUOTA_CHECK_MAX_FILES_OP, 0);
}

/*
 * ceph_quota_is_max_bytes_exceeded - check if we can write to a file
 * @inode:      inode being written
 * @newsize:    new size if write succeeds
 *
 * This functions returns true is max_bytes quota allows a file size to reach
 * @newsize; it returns false otherwise.
 */
bool ceph_quota_is_max_bytes_exceeded(struct inode *inode, loff_t newsize)
{
        loff_t size = i_size_read(inode);

        if (!ceph_has_realms_with_quotas(inode))
                return false;

        /* return immediately if we're decreasing file size */
        if (newsize <= size)
                return false;

        return check_quota_exceeded(inode, QUOTA_CHECK_MAX_BYTES_OP, (newsize - size));
}

/*
 * ceph_quota_is_max_bytes_approaching - check if we're reaching max_bytes
 * @inode:      inode being written
 * @newsize:    new size if write succeeds
 *
 * This function returns true if the new file size @newsize will be consuming
 * more than 1/16th of the available quota space; it returns false otherwise.
 */
bool ceph_quota_is_max_bytes_approaching(struct inode *inode, loff_t newsize)
{
        loff_t size = ceph_inode(inode)->i_reported_size;

        if (!ceph_has_realms_with_quotas(inode))
                return false;

        /* return immediately if we're decreasing file size */
        if (newsize <= size)
                return false;

        return check_quota_exceeded(inode, QUOTA_CHECK_MAX_BYTES_APPROACHING_OP,
                                    (newsize - size));
}

/*
 * ceph_quota_update_statfs - if root has quota update statfs with quota status
 * @fsc:        filesystem client instance
 * @buf:        statfs to update
 *
 * If the mounted filesystem root has max_bytes quota set, update the filesystem
 * statistics with the quota status.
 *
 * This function returns true if the stats have been updated, false otherwise.
 */
bool ceph_quota_update_statfs(struct ceph_fs_client *fsc, struct kstatfs *buf)
{
        struct ceph_mds_client *mdsc = fsc->mdsc;
        struct ceph_inode_info *ci;
        struct ceph_snap_realm *realm;
        struct inode *in;
        u64 total = 0, used, free;
        bool is_updated = false;

        down_read(&mdsc->snap_rwsem);
        realm = get_quota_realm(mdsc, d_inode(fsc->sb->s_root), true);
        up_read(&mdsc->snap_rwsem);
        if (!realm)
                return false;

        spin_lock(&realm->inodes_with_caps_lock);
        in = realm->inode ? igrab(realm->inode) : NULL;
        spin_unlock(&realm->inodes_with_caps_lock);
        if (in) {
                ci = ceph_inode(in);
                spin_lock(&ci->i_ceph_lock);
                if (ci->i_max_bytes) {
                        total = ci->i_max_bytes >> CEPH_BLOCK_SHIFT;
                        used = ci->i_rbytes >> CEPH_BLOCK_SHIFT;
                        /* It is possible for a quota to be exceeded.
                         * Report 'zero' in that case
                         */
                        free = total > used ? total - used : 0;
                }
                spin_unlock(&ci->i_ceph_lock);
                if (total) {
                        buf->f_blocks = total;
                        buf->f_bfree = free;
                        buf->f_bavail = free;
                        is_updated = true;
                }
                iput(in);
        }
        ceph_put_snap_realm(mdsc, realm);

        return is_updated;
}