/*
  Copyright (c) 2008-2012 Red Hat, Inc. <http://www.redhat.com>
  This file is part of GlusterFS.

  This file is licensed to you under your choice of the GNU Lesser
  General Public License, version 3 or any later version (LGPLv3 or
  later), or the GNU General Public License, version 2 (GPLv2), in all
  cases as published by the Free Software Foundation.
*/

/*
  TODO:
  - handle O_DIRECT
  - maintain offset, flush on lseek
  - ensure efficient memory management in case of random seek
*/

#include <glusterfs/glusterfs.h>
#include <glusterfs/logging.h>
#include <glusterfs/dict.h>
#include <glusterfs/xlator.h>
#include "read-ahead.h"
#include <glusterfs/statedump.h>
#include <assert.h>
#include <sys/time.h>
#include "read-ahead-messages.h"

static void
read_ahead(call_frame_t *frame, ra_file_t *file);

int
ra_open_cbk(call_frame_t *frame, void *cookie, xlator_t *this, int32_t op_ret,
            int32_t op_errno, fd_t *fd, dict_t *xdata)
{
    ra_conf_t *conf = NULL;
    ra_file_t *file = NULL;
    int ret = 0;

    GF_ASSERT(frame);
    GF_VALIDATE_OR_GOTO(frame->this->name, this, unwind);

    conf = this->private;

    if (op_ret == -1) {
        goto unwind;
    }

    file = GF_CALLOC(1, sizeof(*file), gf_ra_mt_ra_file_t);
    if (!file) {
        op_ret = -1;
        op_errno = ENOMEM;
        goto unwind;
    }

    /* If O_DIRECT open, we disable caching on it */

    if ((fd->flags & O_DIRECT) || ((fd->flags & O_ACCMODE) == O_WRONLY))
        file->disabled = 1;

    file->offset = (unsigned long long)0;
    file->conf = conf;
    file->pages.next = &file->pages;
    file->pages.prev = &file->pages;
    file->pages.offset = (unsigned long long)0;
    file->pages.file = file;

    ra_conf_lock(conf);
    {
        file->next = conf->files.next;
        conf->files.next = file;
        file->next->prev = file;
        file->prev = &conf->files;
    }
    ra_conf_unlock(conf);

    file->fd = fd;
    file->page_count = conf->page_count;
    file->page_size = conf->page_size;
    pthread_mutex_init(&file->file_lock, NULL);

    if (!file->disabled) {
        file->page_count = 1;
    }

    ret = fd_ctx_set(fd, this, (uint64_t)(long)file);
    if (ret == -1) {
        gf_msg(frame->this->name, GF_LOG_WARNING, 0, READ_AHEAD_MSG_NO_MEMORY,
               "cannot set read-ahead context"
               "information in fd (%p)",
               fd);
        ra_file_destroy(file);
        op_ret = -1;
        op_errno = ENOMEM;
    }

unwind:
    frame->local = NULL;

    STACK_UNWIND_STRICT(open, frame, op_ret, op_errno, fd, xdata);

    return 0;
}

int
ra_create_cbk(call_frame_t *frame, void *cookie, xlator_t *this, int32_t op_ret,
              int32_t op_errno, fd_t *fd, inode_t *inode, struct iatt *buf,
              struct iatt *preparent, struct iatt *postparent, dict_t *xdata)
{
    ra_conf_t *conf = NULL;
    ra_file_t *file = NULL;
    int ret = 0;

    GF_ASSERT(frame);
    GF_VALIDATE_OR_GOTO(frame->this->name, this, unwind);

    conf = this->private;

    if (op_ret == -1) {
        goto unwind;
    }

    file = GF_CALLOC(1, sizeof(*file), gf_ra_mt_ra_file_t);
    if (!file) {
        op_ret = -1;
        op_errno = ENOMEM;
        goto unwind;
    }

    /* If O_DIRECT open, we disable caching on it */

    if ((fd->flags & O_DIRECT) || ((fd->flags & O_ACCMODE) == O_WRONLY))
        file->disabled = 1;

    file->offset = (unsigned long long)0;
    // file->size = fd->inode->buf.ia_size;
    file->conf = conf;
    file->pages.next = &file->pages;
    file->pages.prev = &file->pages;
    file->pages.offset = (unsigned long long)0;
    file->pages.file = file;

    ra_conf_lock(conf);
    {
        file->next = conf->files.next;
        conf->files.next = file;
        file->next->prev = file;
        file->prev = &conf->files;
    }
    ra_conf_unlock(conf);

    file->fd = fd;
    file->page_count = conf->page_count;
    file->page_size = conf->page_size;
    pthread_mutex_init(&file->file_lock, NULL);

    ret = fd_ctx_set(fd, this, (uint64_t)(long)file);
    if (ret == -1) {
        gf_msg(this->name, GF_LOG_WARNING, 0, READ_AHEAD_MSG_NO_MEMORY,
               "cannot set read ahead context"
               "information in fd (%p)",
               fd);
        ra_file_destroy(file);
        op_ret = -1;
        op_errno = ENOMEM;
    }

unwind:
    STACK_UNWIND_STRICT(create, frame, op_ret, op_errno, fd, inode, buf,
                        preparent, postparent, xdata);

    return 0;
}

int
ra_open(call_frame_t *frame, xlator_t *this, loc_t *loc, int32_t flags,
        fd_t *fd, dict_t *xdata)
{
    GF_ASSERT(frame);
    GF_ASSERT(this);

    STACK_WIND(frame, ra_open_cbk, FIRST_CHILD(this),
               FIRST_CHILD(this)->fops->open, loc, flags, fd, xdata);

    return 0;
}

int
ra_create(call_frame_t *frame, xlator_t *this, loc_t *loc, int32_t flags,
          mode_t mode, mode_t umask, fd_t *fd, dict_t *xdata)
{
    GF_ASSERT(frame);
    GF_ASSERT(this);

    STACK_WIND(frame, ra_create_cbk, FIRST_CHILD(this),
               FIRST_CHILD(this)->fops->create, loc, flags, mode, umask, fd,
               xdata);

    return 0;
}

/* free cache pages between offset and offset+size,
   does not touch pages with frames waiting on it
*/

static void
flush_region(call_frame_t *frame, ra_file_t *file, off_t offset, off_t size,
             int for_write)
{
    ra_page_t *trav = NULL;
    ra_page_t *next = NULL;

    ra_file_lock(file);
    {
        trav = file->pages.next;
        while (trav != &file->pages && trav->offset < (offset + size)) {
            next = trav->next;
            if (trav->offset >= offset) {
                if (!trav->waitq) {
                    ra_page_purge(trav);
                } else {
                    trav->stale = 1;

                    if (for_write) {
                        trav->poisoned = 1;
                    }
                }
            }
            trav = next;
        }
    }
    ra_file_unlock(file);
}

int
ra_release(xlator_t *this, fd_t *fd)
{
    uint64_t tmp_file = 0;
    int ret = 0;

    GF_VALIDATE_OR_GOTO("read-ahead", this, out);
    GF_VALIDATE_OR_GOTO(this->name, fd, out);

    ret = fd_ctx_del(fd, this, &tmp_file);

    if (!ret) {
        ra_file_destroy((ra_file_t *)(long)tmp_file);
    }

out:
    return 0;
}

void
read_ahead(call_frame_t *frame, ra_file_t *file)
{
    off_t ra_offset = 0;
    size_t ra_size = 0;
    off_t trav_offset = 0;
    ra_page_t *trav = NULL;
    off_t cap = 0;
    char fault = 0;

    GF_VALIDATE_OR_GOTO("read-ahead", frame, out);
    GF_VALIDATE_OR_GOTO(frame->this->name, file, out);

    if (!file->page_count) {
        goto out;
    }

    ra_size = file->page_size * file->page_count;
    ra_offset = gf_floor(file->offset, file->page_size);
    cap = file->size ? file->size : file->offset + ra_size;

    while (ra_offset < min(file->offset + ra_size, cap)) {
        ra_file_lock(file);
        {
            trav = ra_page_get(file, ra_offset);
        }
        ra_file_unlock(file);

        if (!trav)
            break;

        ra_offset += file->page_size;
    }

    if (trav) {
        /* comfortable enough */
        goto out;
    }

    trav_offset = ra_offset;

    cap = file->size ? file->size : ra_offset + ra_size;

    while (trav_offset < min(ra_offset + ra_size, cap)) {
        fault = 0;
        ra_file_lock(file);
        {
            trav = ra_page_get(file, trav_offset);
            if (!trav) {
                fault = 1;
                trav = ra_page_create(file, trav_offset);
                if (trav)
                    trav->dirty = 1;
            }
        }
        ra_file_unlock(file);

        if (!trav) {
            /* OUT OF MEMORY */
            break;
        }

        if (fault) {
            gf_msg_trace(frame->this->name, 0, "RA at offset=%" PRId64,
                         trav_offset);
            ra_page_fault(file, frame, trav_offset);
        }
        trav_offset += file->page_size;
    }

out:
    return;
}

int
ra_need_atime_cbk(call_frame_t *frame, void *cookie, xlator_t *this,
                  int32_t op_ret, int32_t op_errno, struct iovec *vector,
                  int32_t count, struct iatt *stbuf, struct iobref *iobref,
                  dict_t *xdata)
{
    GF_ASSERT(frame);
    STACK_DESTROY(frame->root);
    return 0;
}

static void
dispatch_requests(call_frame_t *frame, ra_file_t *file)
{
    ra_local_t *local = NULL;
    ra_conf_t *conf = NULL;
    off_t rounded_offset = 0;
    off_t rounded_end = 0;
    off_t trav_offset = 0;
    ra_page_t *trav = NULL;
    call_frame_t *ra_frame = NULL;
    char need_atime_update = 1;
    char fault = 0;

    GF_VALIDATE_OR_GOTO("read-ahead", frame, out);
    GF_VALIDATE_OR_GOTO(frame->this->name, file, out);

    local = frame->local;
    conf = file->conf;

    rounded_offset = gf_floor(local->offset, file->page_size);
    rounded_end = gf_roof(local->offset + local->size, file->page_size);

    trav_offset = rounded_offset;

    while (trav_offset < rounded_end) {
        fault = 0;

        ra_file_lock(file);
        {
            trav = ra_page_get(file, trav_offset);
            if (!trav) {
                trav = ra_page_create(file, trav_offset);
                if (!trav) {
                    local->op_ret = -1;
                    local->op_errno = ENOMEM;
                    goto unlock;
                }
                fault = 1;
                need_atime_update = 0;
            }
            trav->dirty = 0;

            if (trav->ready) {
                gf_msg_trace(frame->this->name, 0, "HIT at offset=%" PRId64 ".",
                             trav_offset);
                ra_frame_fill(trav, frame);
            } else {
                gf_msg_trace(frame->this->name, 0,
                             "IN-TRANSIT at "
                             "offset=%" PRId64 ".",
                             trav_offset);
                ra_wait_on_page(trav, frame);
                need_atime_update = 0;
            }
        }
    unlock:
        ra_file_unlock(file);

        if (local->op_ret == -1) {
            goto out;
        }

        if (fault) {
            gf_msg_trace(frame->this->name, 0, "MISS at offset=%" PRId64 ".",
                         trav_offset);
            ra_page_fault(file, frame, trav_offset);
        }

        trav_offset += file->page_size;
    }

    if (need_atime_update && conf->force_atime_update) {
        /* TODO: use untimens() since readv() can confuse underlying
           io-cache and others */
        ra_frame = copy_frame(frame);
        if (ra_frame == NULL) {
            goto out;
        }

        STACK_WIND(ra_frame, ra_need_atime_cbk, FIRST_CHILD(frame->this),
                   FIRST_CHILD(frame->this)->fops->readv, file->fd, 1, 1, 0,
                   NULL);
    }

out:
    return;
}

int
ra_readv_disabled_cbk(call_frame_t *frame, void *cookie, xlator_t *this,
                      int32_t op_ret, int32_t op_errno, struct iovec *vector,
                      int32_t count, struct iatt *stbuf, struct iobref *iobref,
                      dict_t *xdata)
{
    GF_ASSERT(frame);

    STACK_UNWIND_STRICT(readv, frame, op_ret, op_errno, vector, count, stbuf,
                        iobref, xdata);

    return 0;
}

int
ra_readv(call_frame_t *frame, xlator_t *this, fd_t *fd, size_t size,
         off_t offset, uint32_t flags, dict_t *xdata)
{
    ra_file_t *file = NULL;
    ra_local_t *local = NULL;
    ra_conf_t *conf = NULL;
    int op_errno = EINVAL;
    char expected_offset = 1;
    uint64_t tmp_file = 0;

    GF_ASSERT(frame);
    GF_VALIDATE_OR_GOTO(frame->this->name, this, unwind);
    GF_VALIDATE_OR_GOTO(frame->this->name, fd, unwind);

    conf = this->private;

    gf_msg_trace(this->name, 0,
                 "NEW REQ at offset=%" PRId64 " for size=%" GF_PRI_SIZET "",
                 offset, size);

    fd_ctx_get(fd, this, &tmp_file);
    file = (ra_file_t *)(long)tmp_file;

    if (!file || file->disabled) {
        goto disabled;
    }

    if (file->offset != offset) {
        gf_msg_trace(this->name, 0,
                     "unexpected offset (%" PRId64 " != %" PRId64
                     ") "
                     "resetting",
                     file->offset, offset);

        expected_offset = file->expected = file->page_count = 0;
    } else {
        gf_msg_trace(this->name, 0,
                     "expected offset (%" PRId64 ") when page_count=%d", offset,
                     file->page_count);

        if (file->expected < (file->page_size * conf->page_count)) {
            file->expected += size;
            file->page_count = min((file->expected / file->page_size),
                                   conf->page_count);
        }
    }

    if (!expected_offset) {
        flush_region(frame, file, 0, file->pages.prev->offset + 1, 0);
    }

    local = mem_get0(this->local_pool);
    if (!local) {
        op_errno = ENOMEM;
        goto unwind;
    }

    local->fd = fd;
    local->offset = offset;
    local->size = size;
    local->wait_count = 1;

    local->fill.next = &local->fill;
    local->fill.prev = &local->fill;

    pthread_mutex_init(&local->local_lock, NULL);

    frame->local = local;

    dispatch_requests(frame, file);

    flush_region(frame, file, 0, gf_floor(offset, file->page_size), 0);

    read_ahead(frame, file);

    file->offset = offset + size;

    ra_frame_return(frame);

    return 0;

unwind:
    STACK_UNWIND_STRICT(readv, frame, -1, op_errno, NULL, 0, NULL, NULL, NULL);

    return 0;

disabled:
    STACK_WIND(frame, ra_readv_disabled_cbk, FIRST_CHILD(frame->this),
               FIRST_CHILD(frame->this)->fops->readv, fd, size, offset, flags,
               xdata);
    return 0;
}

int
ra_flush_cbk(call_frame_t *frame, void *cookie, xlator_t *this, int32_t op_ret,
             int32_t op_errno, dict_t *xdata)
{
    GF_ASSERT(frame);
    STACK_UNWIND_STRICT(flush, frame, op_ret, op_errno, xdata);
    return 0;
}

int
ra_fsync_cbk(call_frame_t *frame, void *cookie, xlator_t *this, int32_t op_ret,
             int32_t op_errno, struct iatt *prebuf, struct iatt *postbuf,
             dict_t *xdata)
{
    GF_ASSERT(frame);
    STACK_UNWIND_STRICT(fsync, frame, op_ret, op_errno, prebuf, postbuf, xdata);
    return 0;
}

int
ra_flush(call_frame_t *frame, xlator_t *this, fd_t *fd, dict_t *xdata)
{
    int32_t op_errno = EINVAL;

    GF_ASSERT(frame);
    GF_VALIDATE_OR_GOTO(frame->this->name, this, unwind);
    GF_VALIDATE_OR_GOTO(frame->this->name, fd, unwind);

    STACK_WIND(frame, ra_flush_cbk, FIRST_CHILD(this),
               FIRST_CHILD(this)->fops->flush, fd, xdata);
    return 0;

unwind:
    STACK_UNWIND_STRICT(flush, frame, -1, op_errno, NULL);
    return 0;
}

int
ra_fsync(call_frame_t *frame, xlator_t *this, fd_t *fd, int32_t datasync,
         dict_t *xdata)
{
    int32_t op_errno = EINVAL;

    GF_ASSERT(frame);
    GF_VALIDATE_OR_GOTO(frame->this->name, this, unwind);
    GF_VALIDATE_OR_GOTO(frame->this->name, fd, unwind);

    STACK_WIND(frame, ra_fsync_cbk, FIRST_CHILD(this),
               FIRST_CHILD(this)->fops->fsync, fd, datasync, xdata);
    return 0;

unwind:
    STACK_UNWIND_STRICT(fsync, frame, -1, op_errno, NULL, NULL, NULL);
    return 0;
}

int
ra_writev_cbk(call_frame_t *frame, void *cookie, xlator_t *this, int32_t op_ret,
              int32_t op_errno, struct iatt *prebuf, struct iatt *postbuf,
              dict_t *xdata)
{
    ra_file_t *file = NULL;

    GF_ASSERT(frame);

    file = frame->local;

    if (file) {
        flush_region(frame, file, 0, file->pages.prev->offset + 1, 1);
    }

    frame->local = NULL;
    STACK_UNWIND_STRICT(writev, frame, op_ret, op_errno, prebuf, postbuf,
                        xdata);
    return 0;
}

int
ra_writev(call_frame_t *frame, xlator_t *this, fd_t *fd, struct iovec *vector,
          int32_t count, off_t offset, uint32_t flags, struct iobref *iobref,
          dict_t *xdata)
{
    ra_file_t *file = NULL;
    uint64_t tmp_file = 0;
    int32_t op_errno = EINVAL;
    inode_t *inode = NULL;
    fd_t *iter_fd = NULL;

    GF_ASSERT(frame);
    GF_VALIDATE_OR_GOTO(frame->this->name, this, unwind);
    GF_VALIDATE_OR_GOTO(frame->this->name, fd, unwind);

    inode = fd->inode;

    LOCK(&inode->lock);
    {
        list_for_each_entry(iter_fd, &inode->fd_list, inode_list)
        {
            tmp_file = 0;
            fd_ctx_get(iter_fd, this, &tmp_file);
            file = (ra_file_t *)(long)tmp_file;

            if (!file)
                continue;

            if (iter_fd == fd)
                frame->local = file;

            flush_region(frame, file, 0, file->pages.prev->offset + 1, 1);

            /* reset the read-ahead counters too */
            file->expected = file->page_count = 0;
        }
    }
    UNLOCK(&inode->lock);

    STACK_WIND(frame, ra_writev_cbk, FIRST_CHILD(this),
               FIRST_CHILD(this)->fops->writev, fd, vector, count, offset,
               flags, iobref, xdata);

    return 0;

unwind:
    STACK_UNWIND_STRICT(writev, frame, -1, op_errno, NULL, NULL, NULL);
    return 0;
}

int
ra_truncate_cbk(call_frame_t *frame, void *cookie, xlator_t *this,
                int32_t op_ret, int32_t op_errno, struct iatt *prebuf,
                struct iatt *postbuf, dict_t *xdata)
{
    GF_ASSERT(frame);

    STACK_UNWIND_STRICT(truncate, frame, op_ret, op_errno, prebuf, postbuf,
                        xdata);
    return 0;
}

int
ra_attr_cbk(call_frame_t *frame, void *cookie, xlator_t *this, int32_t op_ret,
            int32_t op_errno, struct iatt *buf, dict_t *xdata)
{
    GF_ASSERT(frame);

    STACK_UNWIND_STRICT(stat, frame, op_ret, op_errno, buf, xdata);
    return 0;
}

int
ra_truncate(call_frame_t *frame, xlator_t *this, loc_t *loc, off_t offset,
            dict_t *xdata)
{
    ra_file_t *file = NULL;
    fd_t *iter_fd = NULL;
    inode_t *inode = NULL;
    uint64_t tmp_file = 0;
    int32_t op_errno = EINVAL;

    GF_ASSERT(frame);
    GF_VALIDATE_OR_GOTO(frame->this->name, this, unwind);
    GF_VALIDATE_OR_GOTO(frame->this->name, loc, unwind);

    inode = loc->inode;

    LOCK(&inode->lock);
    {
        list_for_each_entry(iter_fd, &inode->fd_list, inode_list)
        {
            tmp_file = 0;
            fd_ctx_get(iter_fd, this, &tmp_file);
            file = (ra_file_t *)(long)tmp_file;

            if (!file)
                continue;
            /*
             * Truncation invalidates reads just like writing does.
             * TBD: this seems to flush more than it should.  The
             * only time we should flush at all is when we're
             * shortening (not lengthening) the file, and then only
             * from new EOF to old EOF.  The same problem exists in
             * ra_ftruncate.
             */
            flush_region(frame, file, 0, file->pages.prev->offset + 1, 1);
        }
    }
    UNLOCK(&inode->lock);

    STACK_WIND(frame, ra_truncate_cbk, FIRST_CHILD(this),
               FIRST_CHILD(this)->fops->truncate, loc, offset, xdata);
    return 0;

unwind:
    STACK_UNWIND_STRICT(truncate, frame, -1, op_errno, NULL, NULL, NULL);
    return 0;
}

void
ra_page_dump(struct ra_page *page)
{
    int i = 0;
    call_frame_t *frame = NULL;
    char key[GF_DUMP_MAX_BUF_LEN] = {
        0,
    };
    ra_waitq_t *trav = NULL;

    if (page == NULL) {
        goto out;
    }

    gf_proc_dump_write("offset", "%" PRId64, page->offset);

    gf_proc_dump_write("size", "%" GF_PRI_SIZET, page->size);

    gf_proc_dump_write("dirty", "%s", page->dirty ? "yes" : "no");

    gf_proc_dump_write("poisoned", "%s", page->poisoned ? "yes" : "no");

    gf_proc_dump_write("ready", "%s", page->ready ? "yes" : "no");

    for (trav = page->waitq; trav; trav = trav->next) {
        frame = trav->data;
        sprintf(key, "waiting-frame[%d]", i++);
        gf_proc_dump_write(key, "%" PRId64, frame->root->unique);
    }

out:
    return;
}

int32_t
ra_fdctx_dump(xlator_t *this, fd_t *fd)
{
    ra_file_t *file = NULL;
    ra_page_t *page = NULL;
    int32_t ret = 0, i = 0;
    uint64_t tmp_file = 0;
    char *path = NULL;
    char key_prefix[GF_DUMP_MAX_BUF_LEN] = {
        0,
    };

    fd_ctx_get(fd, this, &tmp_file);
    file = (ra_file_t *)(long)tmp_file;

    if (file == NULL) {
        ret = 0;
        goto out;
    }

    gf_proc_dump_build_key(key_prefix, "xlator.performance.read-ahead", "file");

    gf_proc_dump_add_section("%s", key_prefix);

    ret = __inode_path(fd->inode, NULL, &path);
    if (path != NULL) {
        gf_proc_dump_write("path", "%s", path);
        GF_FREE(path);
    }

    gf_proc_dump_write("fd", "%p", fd);

    gf_proc_dump_write("disabled", "%s", file->disabled ? "yes" : "no");

    if (file->disabled) {
        ret = 0;
        goto out;
    }

    gf_proc_dump_write("page-size", "%" PRId64, file->page_size);

    gf_proc_dump_write("page-count", "%u", file->page_count);

    gf_proc_dump_write("next-expected-offset-for-sequential-reads", "%" PRId64,
                       file->offset);

    for (page = file->pages.next; page != &file->pages; page = page->next) {
        gf_proc_dump_write("page", "%d: %p", i++, (void *)page);
        ra_page_dump(page);
    }

    ret = 0;
out:
    return ret;
}

int
ra_fstat(call_frame_t *frame, xlator_t *this, fd_t *fd, dict_t *xdata)
{
    ra_file_t *file = NULL;
    fd_t *iter_fd = NULL;
    inode_t *inode = NULL;
    uint64_t tmp_file = 0;
    int32_t op_errno = EINVAL;
    ra_conf_t *conf = NULL;

    conf = this->private;

    GF_ASSERT(frame);
    GF_VALIDATE_OR_GOTO(frame->this->name, this, unwind);
    GF_VALIDATE_OR_GOTO(frame->this->name, fd, unwind);

    inode = fd->inode;

    if (conf->force_atime_update) {
        LOCK(&inode->lock);
        {
            list_for_each_entry(iter_fd, &inode->fd_list, inode_list)
            {
                tmp_file = 0;
                fd_ctx_get(iter_fd, this, &tmp_file);
                file = (ra_file_t *)(long)tmp_file;

                if (!file)
                    continue;
                flush_region(frame, file, 0, file->pages.prev->offset + 1, 0);
            }
        }
        UNLOCK(&inode->lock);
    }

    STACK_WIND(frame, ra_attr_cbk, FIRST_CHILD(this),
               FIRST_CHILD(this)->fops->fstat, fd, xdata);
    return 0;

unwind:
    STACK_UNWIND_STRICT(stat, frame, -1, op_errno, NULL, NULL);
    return 0;
}

int
ra_ftruncate(call_frame_t *frame, xlator_t *this, fd_t *fd, off_t offset,
             dict_t *xdata)
{
    ra_file_t *file = NULL;
    fd_t *iter_fd = NULL;
    inode_t *inode = NULL;
    uint64_t tmp_file = 0;
    int32_t op_errno = EINVAL;

    GF_ASSERT(frame);
    GF_VALIDATE_OR_GOTO(frame->this->name, this, unwind);
    GF_VALIDATE_OR_GOTO(frame->this->name, fd, unwind);

    inode = fd->inode;

    LOCK(&inode->lock);
    {
        list_for_each_entry(iter_fd, &inode->fd_list, inode_list)
        {
            tmp_file = 0;
            fd_ctx_get(iter_fd, this, &tmp_file);
            file = (ra_file_t *)(long)tmp_file;
            if (!file)
                continue;
            /*
             * Truncation invalidates reads just like writing does.
             * TBD: this seems to flush more than it should.  The
             * only time we should flush at all is when we're
             * shortening (not lengthening) the file, and then only
             * from new EOF to old EOF.  The same problem exists in
             * ra_truncate.
             */
            flush_region(frame, file, 0, file->pages.prev->offset + 1, 1);
        }
    }
    UNLOCK(&inode->lock);

    STACK_WIND(frame, ra_truncate_cbk, FIRST_CHILD(this),
               FIRST_CHILD(this)->fops->ftruncate, fd, offset, xdata);
    return 0;

unwind:
    STACK_UNWIND_STRICT(truncate, frame, -1, op_errno, NULL, NULL, NULL);
    return 0;
}

int
ra_discard_cbk(call_frame_t *frame, void *cookie, xlator_t *this,
               int32_t op_ret, int32_t op_errno, struct iatt *prebuf,
               struct iatt *postbuf, dict_t *xdata)
{
    GF_ASSERT(frame);

    STACK_UNWIND_STRICT(discard, frame, op_ret, op_errno, prebuf, postbuf,
                        xdata);
    return 0;
}

static int
ra_discard(call_frame_t *frame, xlator_t *this, fd_t *fd, off_t offset,
           size_t len, dict_t *xdata)
{
    ra_file_t *file = NULL;
    fd_t *iter_fd = NULL;
    inode_t *inode = NULL;
    uint64_t tmp_file = 0;
    int32_t op_errno = EINVAL;

    GF_ASSERT(frame);
    GF_VALIDATE_OR_GOTO(frame->this->name, this, unwind);
    GF_VALIDATE_OR_GOTO(frame->this->name, fd, unwind);

    inode = fd->inode;

    LOCK(&inode->lock);
    {
        list_for_each_entry(iter_fd, &inode->fd_list, inode_list)
        {
            tmp_file = 0;
            fd_ctx_get(iter_fd, this, &tmp_file);
            file = (ra_file_t *)(long)tmp_file;
            if (!file)
                continue;

            flush_region(frame, file, offset, len, 1);
        }
    }
    UNLOCK(&inode->lock);

    STACK_WIND(frame, ra_discard_cbk, FIRST_CHILD(this),
               FIRST_CHILD(this)->fops->discard, fd, offset, len, xdata);
    return 0;

unwind:
    STACK_UNWIND_STRICT(discard, frame, -1, op_errno, NULL, NULL, NULL);
    return 0;
}

int
ra_zerofill_cbk(call_frame_t *frame, void *cookie, xlator_t *this,
                int32_t op_ret, int32_t op_errno, struct iatt *prebuf,
                struct iatt *postbuf, dict_t *xdata)
{
    GF_ASSERT(frame);

    STACK_UNWIND_STRICT(zerofill, frame, op_ret, op_errno, prebuf, postbuf,
                        xdata);
    return 0;
}

static int
ra_zerofill(call_frame_t *frame, xlator_t *this, fd_t *fd, off_t offset,
            off_t len, dict_t *xdata)
{
    ra_file_t *file = NULL;
    fd_t *iter_fd = NULL;
    inode_t *inode = NULL;
    uint64_t tmp_file = 0;
    int32_t op_errno = EINVAL;

    GF_ASSERT(frame);
    GF_VALIDATE_OR_GOTO(frame->this->name, this, unwind);
    GF_VALIDATE_OR_GOTO(frame->this->name, fd, unwind);

    inode = fd->inode;

    LOCK(&inode->lock);
    {
        list_for_each_entry(iter_fd, &inode->fd_list, inode_list)
        {
            tmp_file = 0;
            fd_ctx_get(iter_fd, this, &tmp_file);
            file = (ra_file_t *)(long)tmp_file;
            if (!file)
                continue;

            flush_region(frame, file, offset, len, 1);
        }
    }
    UNLOCK(&inode->lock);

    STACK_WIND(frame, ra_zerofill_cbk, FIRST_CHILD(this),
               FIRST_CHILD(this)->fops->zerofill, fd, offset, len, xdata);
    return 0;

unwind:
    STACK_UNWIND_STRICT(zerofill, frame, -1, op_errno, NULL, NULL, NULL);
    return 0;
}

int
ra_priv_dump(xlator_t *this)
{
    ra_conf_t *conf = NULL;
    int ret = -1;
    char key_prefix[GF_DUMP_MAX_BUF_LEN] = {
        0,
    };

    if (!this) {
        goto out;
    }

    conf = this->private;
    if (!conf) {
        gf_msg(this->name, GF_LOG_WARNING, 0, READ_AHEAD_MSG_XLATOR_CONF_NULL,
               "conf null in xlator");
        goto out;
    }

    gf_proc_dump_build_key(key_prefix, "xlator.performance.read-ahead", "priv");

    gf_proc_dump_add_section("%s", key_prefix);

    ret = pthread_mutex_trylock(&conf->conf_lock);
    if (ret)
        goto out;
    {
        gf_proc_dump_write("page_size", "%" PRIu64, conf->page_size);
        gf_proc_dump_write("page_count", "%d", conf->page_count);
        gf_proc_dump_write("force_atime_update", "%d",
                           conf->force_atime_update);
    }
    pthread_mutex_unlock(&conf->conf_lock);

    ret = 0;
out:
    if (ret && conf) {
        gf_proc_dump_write("Unable to dump priv",
                           "(Lock acquisition failed) %s", this->name);
    }
    return ret;
}

int32_t
mem_acct_init(xlator_t *this)
{
    int ret = -1;

    if (!this) {
        goto out;
    }

    ret = xlator_mem_acct_init(this, gf_ra_mt_end + 1);

    if (ret != 0) {
        gf_msg(this->name, GF_LOG_ERROR, ENOMEM, READ_AHEAD_MSG_NO_MEMORY,
               "Memory accounting init"
               "failed");
    }

out:
    return ret;
}

int
reconfigure(xlator_t *this, dict_t *options)
{
    ra_conf_t *conf = NULL;
    int ret = -1;

    GF_VALIDATE_OR_GOTO("read-ahead", this, out);
    GF_VALIDATE_OR_GOTO("read-ahead", this->private, out);

    conf = this->private;

    GF_OPTION_RECONF("page-count", conf->page_count, options, uint32, out);

    GF_OPTION_RECONF("page-size", conf->page_size, options, size_uint64, out);

    GF_OPTION_RECONF("pass-through", this->pass_through, options, bool, out);

    ret = 0;
out:
    return ret;
}

int
init(xlator_t *this)
{
    ra_conf_t *conf = NULL;
    int32_t ret = -1;

    GF_VALIDATE_OR_GOTO("read-ahead", this, out);

    if (!this->children || this->children->next) {
        gf_msg(this->name, GF_LOG_ERROR, 0,
               READ_AHEAD_MSG_XLATOR_CHILD_MISCONFIGURED,
               "FATAL: read-ahead not configured with exactly one"
               " child");
        goto out;
    }

    if (!this->parents) {
        gf_msg(this->name, GF_LOG_WARNING, 0, READ_AHEAD_MSG_VOL_MISCONFIGURED,
               "dangling volume. check volfile ");
    }

    conf = (void *)GF_CALLOC(1, sizeof(*conf), gf_ra_mt_ra_conf_t);
    if (conf == NULL) {
        goto out;
    }

    conf->page_size = this->ctx->page_size;

    GF_OPTION_INIT("page-size", conf->page_size, size_uint64, out);

    GF_OPTION_INIT("page-count", conf->page_count, uint32, out);

    GF_OPTION_INIT("force-atime-update", conf->force_atime_update, bool, out);

    GF_OPTION_INIT("pass-through", this->pass_through, bool, out);

    conf->files.next = &conf->files;
    conf->files.prev = &conf->files;

    pthread_mutex_init(&conf->conf_lock, NULL);

    this->local_pool = mem_pool_new(ra_local_t, 64);
    if (!this->local_pool) {
        ret = -1;
        gf_msg(this->name, GF_LOG_ERROR, ENOMEM, READ_AHEAD_MSG_NO_MEMORY,
               "failed to create local_t's memory pool");
        goto out;
    }

    this->private = conf;
    ret = 0;

out:
    if (ret == -1) {
        GF_FREE(conf);
    }

    return ret;
}

void
fini(xlator_t *this)
{
    ra_conf_t *conf = NULL;

    GF_VALIDATE_OR_GOTO("read-ahead", this, out);

    conf = this->private;
    if (conf == NULL) {
        goto out;
    }

    this->private = NULL;

    /* The files structures allocated in open and create are not deleted.
     * until that is freed, marking the below assert as warning.
    GF_ASSERT ((conf->files.next == &conf->files)
               && (conf->files.prev == &conf->files));
    */
    if (!((conf->files.next == &conf->files) &&
          (conf->files.prev == &conf->files))) {
        gf_msg(this->name, GF_LOG_INFO, 0,
               READ_AHEAD_MSG_UNDESTROYED_FILE_FOUND,
               "undestroyed read ahead file structures found");
    }

    pthread_mutex_destroy(&conf->conf_lock);
    GF_FREE(conf);

out:
    return;
}

struct xlator_fops fops = {
    .open = ra_open,
    .create = ra_create,
    .readv = ra_readv,
    .writev = ra_writev,
    .flush = ra_flush,
    .fsync = ra_fsync,
    .truncate = ra_truncate,
    .ftruncate = ra_ftruncate,
    .fstat = ra_fstat,
    .discard = ra_discard,
    .zerofill = ra_zerofill,
};

struct xlator_cbks cbks = {
    .release = ra_release,
};

struct xlator_dumpops dumpops = {
    .priv = ra_priv_dump,
    .fdctx = ra_fdctx_dump,
};

struct volume_options options[] = {
    {
        .key = {"read-ahead"},
        .type = GF_OPTION_TYPE_BOOL,
        .default_value = "off",
        .description = "enable/disable read-ahead",
        .op_version = {GD_OP_VERSION_6_0},
        .flags = OPT_FLAG_SETTABLE,
    },
    {.key = {"force-atime-update"},
     .type = GF_OPTION_TYPE_BOOL,
     .op_version = {1},
     .tags = {"read-ahead"},
     .default_value = "false"},
    {.key = {"page-count"},
     .type = GF_OPTION_TYPE_INT,
     .min = 1,
     .max = 16,
     .default_value = "4",
     .op_version = {1},
     .tags = {"read-ahead"},
     .description = "Number of pages that will be pre-fetched"},
    {.key = {"page-size"},
     .type = GF_OPTION_TYPE_SIZET,
     .min = 4096,
     .max = 1048576 * 64,
     .default_value = "131072",
     .op_version = {1},
     .flags = OPT_FLAG_SETTABLE | OPT_FLAG_DOC | OPT_FLAG_CLIENT_OPT,
     .tags = {"read-ahead"},
     .description = "Page size with which read-ahead performs server I/O"},
    {.key = {"pass-through"},
     .type = GF_OPTION_TYPE_BOOL,
     .default_value = "false",
     .op_version = {GD_OP_VERSION_4_1_0},
     .flags = OPT_FLAG_SETTABLE | OPT_FLAG_DOC | OPT_FLAG_CLIENT_OPT,
     .tags = {"read-ahead"},
     .description = "Enable/Disable read ahead translator"},
    {.key = {NULL}},
};

xlator_api_t xlator_api = {
    .init = init,
    .fini = fini,
    .reconfigure = reconfigure,
    .mem_acct_init = mem_acct_init,
    .op_version = {1}, /* Present from the initial version */
    .dumpops = &dumpops,
    .fops = &fops,
    .cbks = &cbks,
    .options = options,
    .identifier = "read-ahead",
    .category = GF_MAINTAINED,
};