rw.c

lustre 1.6.5 source code

                offset = (pos & ~CFS_PAGE_MASK);
                index = pos >> CFS_PAGE_SHIFT;
                bytes = CFS_PAGE_SIZE - offset;
                if (bytes > count)
                        bytes = count;

                /* prevent read beyond file range */
                if (/* local_lock && */
                    cmd == OBD_BRW_READ && pos + bytes >= st->st_size) {
                        if (pos >= st->st_size)
                                break;
                        bytes = st->st_size - pos;
                }

                /* prepare page for this index */
                page->index = index;
                page->addr = buf - offset;

                page->_offset = offset;
                page->_count = bytes;

                page++;
                npages++;
                count -= bytes;
                pos += bytes;
                buf += bytes;

                group->lig_rwcount += bytes;
                ret_bytes += bytes;
        } while (count);

        group->lig_npages += npages;

        for (i = 0, page = pages; i < npages;
             i++, page++, llap++, llap_cookie += llap_cookie_size){
                llap->llap_magic = LLAP_MAGIC;
                llap->llap_cookie = llap_cookie;
                rc = obd_prep_async_page(exp, lsm, NULL, page,
                                         (obd_off)page->index << CFS_PAGE_SHIFT,
                                         &llu_async_page_ops,
                                         llap, &llap->llap_cookie,
                                         1 /* no cache in liblustre at all */,
                                         NULL);
                if (rc) {
                        LASSERT(rc < 0);
                        llap->llap_cookie = NULL;
                        RETURN(rc);
                }
                CDEBUG(D_CACHE, "llap %p page %p group %p obj off "LPU64"\n",
                       llap, page, llap->llap_cookie,
                       (obd_off)pages->index << CFS_PAGE_SHIFT);
                page->private = (unsigned long)llap;
                llap->llap_page = page;
                llap->llap_inode = group->lig_inode;

                rc = obd_queue_group_io(exp, lsm, NULL, group->lig_oig,
                                        llap->llap_cookie, cmd,
                                        page->_offset, page->_count,
                                        group->lig_params->lrp_brw_flags,
                                        ASYNC_READY | ASYNC_URGENT |
                                        ASYNC_COUNT_STABLE | ASYNC_GROUP_SYNC);
                if (!local_lock && cmd == OBD_BRW_READ) {
                        /*
                         * In OST-side locking case short reads cannot be
                         * detected properly.
                         *
                         * The root of the problem is that
                         *
                         * kms = lov_merge_size(lsm, 1);
                         * if (end >= kms)
                         *         glimpse_size(inode);
                         * else
                         *         st->st_size = kms;
                         *
                         * logic in the read code (both llite and liblustre)
                         * only works correctly when client holds DLM lock on
                         * [start, end]. Without DLM lock KMS can be
                         * completely out of date, and client can either make
                         * spurious short-read (missing concurrent write), or
                         * return stale data (missing concurrent
                         * truncate). For llite client this is fatal, because
                         * incorrect data are cached and can be later sent
                         * back to the server (vide bug 5047). This is hard to
                         * fix by handling short-reads on the server, as there
                         * is no easy way to communicate file size (or amount
                         * of bytes read/written) back to the client,
                         * _especially_ because OSC pages can be sliced and
                         * dices into multiple RPCs arbitrary. Fortunately,
                         * liblustre doesn't cache data and the worst case is
                         * that we get race with concurrent write or truncate.
                         */
                }
                if (rc) {
                        LASSERT(rc < 0);
                        RETURN(rc);
                }

                llap->llap_queued = 1;
        }

        RETURN(ret_bytes);
}

static
struct llu_io_group * get_io_group(struct inode *inode, int maxpages,
                                   struct lustre_rw_params *params)
{
        struct llu_io_group *group;
        int rc;

        if (!llap_cookie_size)
                llap_cookie_size = obd_prep_async_page(llu_i2obdexp(inode),
                                                       NULL, NULL, NULL, 0,
                                                       NULL, NULL, NULL, 0,
                                                       NULL);

        OBD_ALLOC(group, LLU_IO_GROUP_SIZE(maxpages));
        if (!group)
                return ERR_PTR(-ENOMEM);

        I_REF(inode);
        group->lig_inode = inode;
        group->lig_maxpages = maxpages;
        group->lig_params = params;
        group->lig_llaps = (struct ll_async_page *)(group + 1);
        group->lig_pages = (struct page *)(&group->lig_llaps[maxpages]);
        group->lig_llap_cookies = (void *)(&group->lig_pages[maxpages]);

        rc = oig_init(&group->lig_oig);
        if (rc) {
                OBD_FREE(group, LLU_IO_GROUP_SIZE(maxpages));
                return ERR_PTR(rc);
        }

        return group;
}

static int max_io_pages(ssize_t len, int iovlen)
{
        return (((len + CFS_PAGE_SIZE -1) >> CFS_PAGE_SHIFT) + 2 + iovlen - 1);
}

static
void put_io_group(struct llu_io_group *group)
{
        struct lov_stripe_md *lsm = llu_i2info(group->lig_inode)->lli_smd;
        struct obd_export *exp = llu_i2obdexp(group->lig_inode);
        struct ll_async_page *llap = group->lig_llaps;
        int i;

        for (i = 0; i < group->lig_npages; i++, llap++) {
                if (llap->llap_cookie)
                        obd_teardown_async_page(exp, lsm, NULL,
                                                llap->llap_cookie);
        }

        I_RELE(group->lig_inode);

        oig_release(group->lig_oig);
        OBD_FREE(group, LLU_IO_GROUP_SIZE(group->lig_maxpages));
}

static
ssize_t llu_file_prwv(const struct iovec *iovec, int iovlen,
                        _SYSIO_OFF_T pos, ssize_t len,
                        void *private)
{
        struct llu_io_session *session = (struct llu_io_session *) private;
        struct inode *inode = session->lis_inode;
        struct llu_inode_info *lli = llu_i2info(inode);
        struct intnl_stat *st = llu_i2stat(inode);
        struct ll_file_data *fd = lli->lli_file_data;
        struct lustre_handle lockh = {0};
        struct lov_stripe_md *lsm = lli->lli_smd;
        struct obd_export *exp = NULL;
        struct llu_io_group *iogroup;
        struct lustre_rw_params p;
        struct ost_lvb lvb;
        __u64 kms;
        int err, is_read, iovidx, ret;
        int local_lock;
        ssize_t ret_len = len;
        ENTRY;

        /* in a large iov read/write we'll be repeatedly called.
         * so give a chance to answer cancel ast here
         */
        liblustre_wait_event(0);

        exp = llu_i2obdexp(inode);
        if (exp == NULL)
                RETURN(-EINVAL);

        if (len == 0 || iovlen == 0)
                RETURN(0);

        if (pos + len > lli->lli_maxbytes)
                RETURN(-ERANGE);

        lustre_build_lock_params(session->lis_cmd, lli->lli_open_flags,
                                 lli->lli_sbi->ll_lco.lco_flags,
                                 pos, len, &p);

        iogroup = get_io_group(inode, max_io_pages(len, iovlen), &p);
        if (IS_ERR(iogroup))
                RETURN(PTR_ERR(iogroup));

        local_lock = p.lrp_lock_mode != LCK_NL;

        err = llu_extent_lock(fd, inode, lsm, p.lrp_lock_mode, &p.lrp_policy,
                              &lockh, p.lrp_ast_flags);
        if (err != ELDLM_OK)
                GOTO(err_put, err);

        is_read = (session->lis_cmd == OBD_BRW_READ);
        if (is_read) {
                /*
                 * If OST-side locking is used, KMS can be completely out of
                 * date, and, hence, cannot be used for short-read
                 * detection. Rely in OST to handle short reads in that case.
                 */
                inode_init_lvb(inode, &lvb);
                obd_merge_lvb(exp, lsm, &lvb, 1);
                kms = lvb.lvb_size;
                /* extent.end is last byte of the range */
                if (p.lrp_policy.l_extent.end >= kms) {
                        /* A glimpse is necessary to determine whether
                         * we return a short read or some zeroes at
                         * the end of the buffer
                         *
                         * In the case of OST-side locking KMS can be
                         * completely out of date and short-reads maybe
                         * mishandled. See llu_queue_pio() for more detailed
                         * comment.
                         */
                        if ((err = llu_glimpse_size(inode))) {
                                GOTO(err_unlock, err);
                        }
                } else {
                        st->st_size = kms;
                }
        } else if (lli->lli_open_flags & O_APPEND) {
                pos = st->st_size;
        }

        for (iovidx = 0; iovidx < iovlen; iovidx++) {
                char *buf = (char *) iovec[iovidx].iov_base;
                size_t count = iovec[iovidx].iov_len;

                if (!count)
                        continue;
                if (len < count)
                        count = len;
                if (IS_BAD_PTR(buf) || IS_BAD_PTR(buf + count)) {
                        GOTO(err_unlock, err = -EFAULT);
                }

                if (is_read) {
                        if (/* local_lock && */ pos >= st->st_size)
                                break;
                } else {
                        if (pos >= lli->lli_maxbytes) {
                                GOTO(err_unlock, err = -EFBIG);
                        }
                        if (pos + count >= lli->lli_maxbytes)
                                count = lli->lli_maxbytes - pos;
                }

                ret = llu_queue_pio(session->lis_cmd, iogroup, buf, count, pos);
                if (ret < 0) {
                        GOTO(err_unlock, err = ret);
                } else {
                        pos += ret;
                        if (!is_read) {
                                LASSERT(ret == count);
                                obd_adjust_kms(exp, lsm, pos, 0);
                                /* file size grow immediately */
                                if (pos > st->st_size)
                                        st->st_size = pos;
                        }
                        len -= ret;
                        if (!len)
                                break;
                }
        }
        LASSERT(len == 0 || is_read); /* libsysio should guarantee this */

        err = obd_trigger_group_io(exp, lsm, NULL, iogroup->lig_oig);
        if (err)
                GOTO(err_unlock, err);

        err = oig_wait(iogroup->lig_oig);
        if (err) {
                CERROR("%s error: %s\n", is_read ? "read" : "write", strerror(-err));
                GOTO(err_unlock, err);
        }

        ret = llu_extent_unlock(fd, inode, lsm, p.lrp_lock_mode, &lockh);
        if (ret)
                CERROR("extent unlock error %d\n", ret);

        session->lis_groups[session->lis_ngroups++] = iogroup;
        RETURN(ret_len);

err_unlock:
        llu_extent_unlock(fd, inode, lsm, p.lrp_lock_mode, &lockh);
err_put:
        put_io_group(iogroup);
        RETURN((ssize_t)err);
}

static
struct llu_io_session *get_io_session(struct inode *ino, int ngroups, int cmd)
{
        struct llu_io_session *session;

        OBD_ALLOC(session, LLU_IO_SESSION_SIZE(ngroups));
        if (!session)
                return NULL;

        I_REF(ino);
        session->lis_inode = ino;
        session->lis_max_groups = ngroups;
        session->lis_cmd = cmd;
        return session;
}

static void put_io_session(struct llu_io_session *session)
{
        int i;

        for (i = 0; i < session->lis_ngroups; i++) {
                if (session->lis_groups[i]) {
                        put_io_group(session->lis_groups[i]);
                        session->lis_groups[i] = NULL;
                }
        }

        I_RELE(session->lis_inode);
        OBD_FREE(session, LLU_IO_SESSION_SIZE(session->lis_max_groups));
}

static int llu_file_rwx(struct inode *ino,
                        struct ioctx *ioctx,
                        int read)
{
        struct llu_io_session *session;
        ssize_t cc;
        int cmd = read ? OBD_BRW_READ : OBD_BRW_WRITE;
        ENTRY;

        LASSERT(ioctx->ioctx_xtvlen >= 0);
        LASSERT(ioctx->ioctx_iovlen >= 0);

        liblustre_wait_event(0);

        if (!ioctx->ioctx_xtvlen)
                RETURN(0);

        /* XXX consider other types later */
        if (S_ISDIR(llu_i2stat(ino)->st_mode))
                RETURN(-EISDIR);
        if (!S_ISREG(llu_i2stat(ino)->st_mode))
                RETURN(-EOPNOTSUPP);

        session = get_io_session(ino, ioctx->ioctx_xtvlen * 2, cmd);
        if (!session)
                RETURN(-ENOMEM);

        cc = _sysio_enumerate_extents(ioctx->ioctx_xtv, ioctx->ioctx_xtvlen,
                                      ioctx->ioctx_iov, ioctx->ioctx_iovlen,
                                      llu_file_prwv, session);

        if (cc >= 0) {
                LASSERT(!ioctx->ioctx_cc);
                ioctx->ioctx_private = session;
                cc = 0;
        } else {
                put_io_session(session);
        }

        liblustre_wait_event(0);
        RETURN(cc);
}

int llu_iop_read(struct inode *ino,
                 struct ioctx *ioctx)
{
        /* BUG: 5972 */
        struct intnl_stat *st = llu_i2stat(ino);
        st->st_atime = CURRENT_TIME;

        return llu_file_rwx(ino, ioctx, 1);
}

int llu_iop_write(struct inode *ino,
                  struct ioctx *ioctx)
{
        struct intnl_stat *st = llu_i2stat(ino);
        st->st_mtime = st->st_ctime = CURRENT_TIME;

        return llu_file_rwx(ino, ioctx, 0);
}

int llu_iop_iodone(struct ioctx *ioctx)
{
        struct llu_io_session *session;
        struct llu_io_group *group;
        int i, err = 0, rc = 0;
        ENTRY;

        liblustre_wait_event(0);

        session = (struct llu_io_session *) ioctx->ioctx_private;
        LASSERT(session);
        LASSERT(!IS_ERR(session));

        for (i = 0; i < session->lis_ngroups; i++) {
                group = session->lis_groups[i];
                if (group) {
                        if (!rc) {
                                err = oig_wait(group->lig_oig);
                                if (err)
                                        rc = err;
                        }
                        if (!rc)
                                ioctx->ioctx_cc += group->lig_rwcount;
                        put_io_group(group);
                        session->lis_groups[i] = NULL;
                }
        }

        if (rc) {
                LASSERT(rc < 0);
                ioctx->ioctx_cc = -1;
                ioctx->ioctx_errno = -rc;
        }

        put_io_session(session);
        ioctx->ioctx_private = NULL;
        liblustre_wait_event(0);

        RETURN(1);
}