1 files changed, 494 insertions, 0 deletions

diff --git a/xlators/cluster/afr/src/afr-read-txn.c b/xlators/cluster/afr/src/afr-read-txn.c
new file mode 100644
index 00000000000..6fc2c75145c
--- /dev/null
+++ b/xlators/cluster/afr/src/afr-read-txn.c
@@ -0,0 +1,494 @@
+/*
+  Copyright (c) 2013 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.
+*/
+
+#include "afr.h"
+#include "afr-transaction.h"
+#include "afr-messages.h"
+
+void
+afr_pending_read_increment(afr_private_t *priv, int child_index)
+{
+    if (child_index < 0 || child_index > priv->child_count)
+        return;
+
+    GF_ATOMIC_INC(priv->pending_reads[child_index]);
+}
+
+void
+afr_pending_read_decrement(afr_private_t *priv, int child_index)
+{
+    if (child_index < 0 || child_index > priv->child_count)
+        return;
+
+    GF_ATOMIC_DEC(priv->pending_reads[child_index]);
+}
+
+void
+afr_read_txn_wind(call_frame_t *frame, xlator_t *this, int subvol)
+{
+    afr_local_t *local = NULL;
+    afr_private_t *priv = NULL;
+
+    local = frame->local;
+    priv = this->private;
+
+    afr_pending_read_decrement(priv, local->read_subvol);
+    local->read_subvol = subvol;
+    afr_pending_read_increment(priv, subvol);
+    local->readfn(frame, this, subvol);
+}
+
+int
+afr_read_txn_next_subvol(call_frame_t *frame, xlator_t *this)
+{
+    afr_local_t *local = NULL;
+    afr_private_t *priv = NULL;
+    int i = 0;
+    int subvol = -1;
+
+    local = frame->local;
+    priv = this->private;
+
+    for (i = 0; i < priv->child_count; i++) {
+        if (!local->readable[i]) {
+            /* don't even bother trying here.
+               just mark as attempted and move on. */
+            local->read_attempted[i] = 1;
+            continue;
+        }
+
+        if (!local->read_attempted[i]) {
+            subvol = i;
+            break;
+        }
+    }
+
+    /* If no more subvols were available for reading, we leave
+       @subvol as -1, which is an indication we have run out of
+       readable subvols. */
+    if (subvol != -1)
+        local->read_attempted[subvol] = 1;
+    afr_read_txn_wind(frame, this, subvol);
+
+    return 0;
+}
+
+static int
+afr_ta_read_txn_done(int ret, call_frame_t *ta_frame, void *opaque)
+{
+    STACK_DESTROY(ta_frame->root);
+    return 0;
+}
+
+static int
+afr_ta_read_txn(void *opaque)
+{
+    call_frame_t *frame = NULL;
+    xlator_t *this = NULL;
+    int read_subvol = -1;
+    int query_child = AFR_CHILD_UNKNOWN;
+    int possible_bad_child = AFR_CHILD_UNKNOWN;
+    int ret = 0;
+    int op_errno = ENOMEM;
+    afr_local_t *local = NULL;
+    afr_private_t *priv = NULL;
+    struct gf_flock flock = {
+        0,
+    };
+    dict_t *xdata_req = NULL;
+    dict_t *xdata_rsp = NULL;
+    int **pending = NULL;
+    loc_t loc = {
+        0,
+    };
+
+    frame = (call_frame_t *)opaque;
+    this = frame->this;
+    local = frame->local;
+    priv = this->private;
+    query_child = local->read_txn_query_child;
+
+    if (query_child == AFR_CHILD_ZERO) {
+        possible_bad_child = AFR_CHILD_ONE;
+    } else if (query_child == AFR_CHILD_ONE) {
+        possible_bad_child = AFR_CHILD_ZERO;
+    } else {
+        /*read_txn_query_child is AFR_CHILD_UNKNOWN*/
+        goto out;
+    }
+
+    /* Ask the query_child to see if it blames the possibly bad one. */
+    xdata_req = dict_new();
+    if (!xdata_req)
+        goto out;
+
+    pending = afr_matrix_create(priv->child_count, AFR_NUM_CHANGE_LOGS);
+    if (!pending)
+        goto out;
+
+    ret = afr_set_pending_dict(priv, xdata_req, pending);
+    if (ret < 0)
+        goto out;
+
+    if (local->fd) {
+        ret = syncop_fxattrop(priv->children[query_child], local->fd,
+                              GF_XATTROP_ADD_ARRAY, xdata_req, NULL, &xdata_rsp,
+                              NULL);
+    } else {
+        ret = syncop_xattrop(priv->children[query_child], &local->loc,
+                             GF_XATTROP_ADD_ARRAY, xdata_req, NULL, &xdata_rsp,
+                             NULL);
+    }
+    if (ret || !xdata_rsp) {
+        gf_msg(this->name, GF_LOG_ERROR, -ret, AFR_MSG_THIN_ARB,
+               "Failed xattrop for gfid %s on %s",
+               uuid_utoa(local->inode->gfid),
+               priv->children[query_child]->name);
+        op_errno = -ret;
+        goto out;
+    }
+
+    if (afr_ta_dict_contains_pending_xattr(xdata_rsp, priv,
+                                           possible_bad_child)) {
+        read_subvol = query_child;
+        goto out;
+    }
+    dict_unref(xdata_rsp);
+    xdata_rsp = NULL;
+
+    /* It doesn't. So query thin-arbiter to see if it blames any data brick. */
+    ret = afr_fill_ta_loc(this, &loc, _gf_true);
+    if (ret) {
+        gf_msg(this->name, GF_LOG_ERROR, -ret, AFR_MSG_THIN_ARB,
+               "Failed to populate thin-arbiter loc for: %s.", loc.name);
+        goto out;
+    }
+    flock.l_type = F_WRLCK; /*start and length are already zero. */
+    ret = syncop_inodelk(priv->children[THIN_ARBITER_BRICK_INDEX],
+                         AFR_TA_DOM_MODIFY, &loc, F_SETLKW, &flock, NULL, NULL);
+    if (ret) {
+        gf_msg(this->name, GF_LOG_ERROR, -ret, AFR_MSG_THIN_ARB,
+               "gfid:%s: Failed to get AFR_TA_DOM_MODIFY lock on %s.",
+               uuid_utoa(local->inode->gfid),
+               priv->pending_key[THIN_ARBITER_BRICK_INDEX]);
+        op_errno = -ret;
+        goto out;
+    }
+
+    ret = syncop_xattrop(priv->children[THIN_ARBITER_BRICK_INDEX], &loc,
+                         GF_XATTROP_ADD_ARRAY, xdata_req, NULL, &xdata_rsp,
+                         NULL);
+    if (ret || !xdata_rsp) {
+        gf_msg(this->name, GF_LOG_ERROR, -ret, AFR_MSG_THIN_ARB,
+               "gfid:%s: Failed xattrop on %s.", uuid_utoa(local->inode->gfid),
+               priv->pending_key[THIN_ARBITER_BRICK_INDEX]);
+        op_errno = -ret;
+        goto unlock;
+    }
+
+    if (!afr_ta_dict_contains_pending_xattr(xdata_rsp, priv, query_child)) {
+        read_subvol = query_child;
+    } else {
+        gf_msg(this->name, GF_LOG_ERROR, EIO, AFR_MSG_THIN_ARB,
+               "Failing read for gfid %s since good brick %s is down",
+               uuid_utoa(local->inode->gfid),
+               priv->children[possible_bad_child]->name);
+        op_errno = EIO;
+    }
+
+unlock:
+    flock.l_type = F_UNLCK;
+    ret = syncop_inodelk(priv->children[THIN_ARBITER_BRICK_INDEX],
+                         AFR_TA_DOM_MODIFY, &loc, F_SETLK, &flock, NULL, NULL);
+    if (ret) {
+        gf_msg(this->name, GF_LOG_ERROR, -ret, AFR_MSG_THIN_ARB,
+               "gfid:%s: Failed to unlock AFR_TA_DOM_MODIFY lock on "
+               "%s.",
+               uuid_utoa(local->inode->gfid),
+               priv->pending_key[THIN_ARBITER_BRICK_INDEX]);
+    }
+out:
+    if (xdata_req)
+        dict_unref(xdata_req);
+    if (xdata_rsp)
+        dict_unref(xdata_rsp);
+    if (pending)
+        afr_matrix_cleanup(pending, priv->child_count);
+    loc_wipe(&loc);
+
+    if (read_subvol == -1) {
+        local->op_ret = -1;
+        local->op_errno = op_errno;
+    }
+    afr_read_txn_wind(frame, this, read_subvol);
+    return ret;
+}
+
+void
+afr_ta_read_txn_synctask(call_frame_t *frame, xlator_t *this)
+{
+    call_frame_t *ta_frame = NULL;
+    afr_local_t *local = NULL;
+    int ret = 0;
+
+    local = frame->local;
+    ta_frame = afr_ta_frame_create(this);
+    if (!ta_frame) {
+        local->op_ret = -1;
+        local->op_errno = ENOMEM;
+        gf_msg(this->name, GF_LOG_ERROR, ENOMEM, AFR_MSG_THIN_ARB,
+               "Failed to create ta_frame");
+        goto out;
+    }
+    ret = synctask_new(this->ctx->env, afr_ta_read_txn, afr_ta_read_txn_done,
+                       ta_frame, frame);
+    if (ret) {
+        gf_msg(this->name, GF_LOG_ERROR, ENOMEM, AFR_MSG_THIN_ARB,
+               "Failed to launch "
+               "afr_ta_read_txn synctask for gfid %s.",
+               uuid_utoa(local->inode->gfid));
+        local->op_ret = -1;
+        local->op_errno = ENOMEM;
+        STACK_DESTROY(ta_frame->root);
+        goto out;
+    }
+    return;
+out:
+    afr_read_txn_wind(frame, this, -1);
+}
+
+int
+afr_read_txn_refresh_done(call_frame_t *frame, xlator_t *this, int err)
+{
+    afr_private_t *priv = NULL;
+    afr_local_t *local = NULL;
+    int read_subvol = -1;
+    inode_t *inode = NULL;
+    int ret = -1;
+    int spb_subvol = -1;
+
+    local = frame->local;
+    inode = local->inode;
+    priv = this->private;
+
+    if (err) {
+        if (!priv->thin_arbiter_count)
+            goto readfn;
+        if (err != EINVAL)
+            goto readfn;
+        /* We need to query the good bricks and/or thin-arbiter.*/
+        afr_ta_read_txn_synctask(frame, this);
+        return 0;
+    }
+
+    read_subvol = afr_read_subvol_select_by_policy(inode, this, local->readable,
+                                                   NULL);
+    if (read_subvol == -1) {
+        err = EIO;
+        goto readfn;
+    }
+
+    if (local->read_attempted[read_subvol]) {
+        afr_read_txn_next_subvol(frame, this);
+        return 0;
+    }
+
+    local->read_attempted[read_subvol] = 1;
+readfn:
+    if (read_subvol == -1) {
+        ret = afr_split_brain_read_subvol_get(inode, this, frame, &spb_subvol);
+        if ((ret == 0) && spb_subvol >= 0)
+            read_subvol = spb_subvol;
+    }
+
+    if (read_subvol == -1) {
+        AFR_SET_ERROR_AND_CHECK_SPLIT_BRAIN(-1, err);
+    }
+    afr_read_txn_wind(frame, this, read_subvol);
+
+    return 0;
+}
+
+int
+afr_read_txn_continue(call_frame_t *frame, xlator_t *this, int subvol)
+{
+    afr_local_t *local = NULL;
+
+    local = frame->local;
+
+    if (!local->refreshed) {
+        local->refreshed = _gf_true;
+        afr_inode_refresh(frame, this, local->inode, NULL,
+                          afr_read_txn_refresh_done);
+    } else {
+        afr_read_txn_next_subvol(frame, this);
+    }
+
+    return 0;
+}
+
+/* afr_read_txn_wipe:
+
+   clean internal variables in @local in order to make
+   it possible to call afr_read_txn() multiple times from
+   the same frame
+*/
+
+void
+afr_read_txn_wipe(call_frame_t *frame, xlator_t *this)
+{
+    afr_local_t *local = NULL;
+    afr_private_t *priv = NULL;
+    int i = 0;
+
+    local = frame->local;
+    priv = this->private;
+
+    local->readfn = NULL;
+
+    if (local->inode)
+        inode_unref(local->inode);
+
+    for (i = 0; i < priv->child_count; i++) {
+        local->read_attempted[i] = 0;
+        local->readable[i] = 0;
+    }
+}
+
+/*
+  afr_read_txn:
+
+  This is the read transaction function. The way it works:
+
+  - Determine read-subvolume from inode ctx.
+
+  - If read-subvolume's generation was stale, refresh ctx once by
+    calling afr_inode_refresh()
+
+    Else make an attempt to read on read-subvolume.
+
+  - If attempted read on read-subvolume fails, refresh ctx once
+    by calling afr_inode_refresh()
+
+  - After ctx refresh, query read-subvolume freshly and attempt
+    read once.
+
+  - If read fails, try every other readable[] subvolume before
+    finally giving up. readable[] elements are set by afr_inode_refresh()
+    based on dirty and pending flags.
+
+  - If file is in split brain in the backend, generation will be
+    kept 0 by afr_inode_refresh() and readable[] will be set 0 for
+    all elements. Therefore reads always fail.
+*/
+
+int
+afr_read_txn(call_frame_t *frame, xlator_t *this, inode_t *inode,
+             afr_read_txn_wind_t readfn, afr_transaction_type type)
+{
+    afr_local_t *local = NULL;
+    afr_private_t *priv = NULL;
+    unsigned char *data = NULL;
+    unsigned char *metadata = NULL;
+    int read_subvol = -1;
+    int event_generation = 0;
+    int ret = -1;
+
+    priv = this->private;
+    local = frame->local;
+    data = alloca0(priv->child_count);
+    metadata = alloca0(priv->child_count);
+
+    afr_read_txn_wipe(frame, this);
+
+    local->readfn = readfn;
+    local->inode = inode_ref(inode);
+    local->is_read_txn = _gf_true;
+    local->transaction.type = type;
+
+    if (priv->quorum_count && !afr_has_quorum(local->child_up, this, NULL)) {
+        local->op_ret = -1;
+        local->op_errno = afr_quorum_errno(priv);
+        goto read;
+    }
+
+    if (!afr_is_consistent_io_possible(local, priv, &local->op_errno)) {
+        local->op_ret = -1;
+        goto read;
+    }
+
+    if (priv->thin_arbiter_count && !afr_ta_has_quorum(priv, local)) {
+        local->op_ret = -1;
+        local->op_errno = -afr_quorum_errno(priv);
+        goto read;
+    }
+
+    if (priv->thin_arbiter_count &&
+        AFR_COUNT(local->child_up, priv->child_count) != priv->child_count) {
+        if (local->child_up[0]) {
+            local->read_txn_query_child = AFR_CHILD_ZERO;
+        } else if (local->child_up[1]) {
+            local->read_txn_query_child = AFR_CHILD_ONE;
+        }
+        afr_ta_read_txn_synctask(frame, this);
+        return 0;
+    }
+
+    ret = afr_inode_read_subvol_get(inode, this, data, metadata,
+                                    &event_generation);
+    if (ret == -1)
+        /* very first transaction on this inode */
+        goto refresh;
+    AFR_INTERSECT(local->readable, data, metadata, priv->child_count);
+
+    gf_msg_debug(this->name, 0,
+                 "%s: generation now vs cached: %d, "
+                 "%d",
+                 uuid_utoa(inode->gfid), local->event_generation,
+                 event_generation);
+    if (afr_is_inode_refresh_reqd(inode, this, local->event_generation,
+                                  event_generation))
+        /* servers have disconnected / reconnected, and possibly
+           rebooted, very likely changing the state of freshness
+           of copies */
+        goto refresh;
+
+    read_subvol = afr_read_subvol_select_by_policy(inode, this, local->readable,
+                                                   NULL);
+
+    if (read_subvol < 0 || read_subvol > priv->child_count) {
+        gf_msg_debug(this->name, 0,
+                     "Unreadable subvolume %d found "
+                     "with event generation %d for gfid %s.",
+                     read_subvol, event_generation, uuid_utoa(inode->gfid));
+        goto refresh;
+    }
+
+    if (!local->child_up[read_subvol]) {
+        /* should never happen, just in case */
+        gf_msg(this->name, GF_LOG_WARNING, 0, AFR_MSG_READ_SUBVOL_ERROR,
+               "subvolume %d is the "
+               "read subvolume in this generation, but is not up",
+               read_subvol);
+        goto refresh;
+    }
+
+    local->read_attempted[read_subvol] = 1;
+
+read:
+    afr_read_txn_wind(frame, this, read_subvol);
+
+    return 0;
+
+refresh:
+    afr_inode_refresh(frame, this, inode, NULL, afr_read_txn_refresh_done);
+
+    return 0;
+}