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/*
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"
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;
local->readfn (frame, this, subvol);
return 0;
}
int
afr_read_txn_refresh_done (call_frame_t *frame, xlator_t *this, int err)
{
afr_local_t *local = NULL;
int read_subvol = 0;
int event_generation = 0;
inode_t *inode = NULL;
int ret = -1;
local = frame->local;
inode = local->inode;
if (err) {
local->op_errno = -err;
local->op_ret = -1;
read_subvol = -1;
goto readfn;
}
ret = afr_inode_read_subvol_type_get (inode, this, local->readable,
&event_generation,
local->transaction.type);
if (ret == -1 || !event_generation) {
/* Even after refresh, we don't have a good
read subvolume. Time to bail */
local->op_ret = -1;
local->op_errno = EIO;
read_subvol = -1;
goto readfn;
}
read_subvol = afr_read_subvol_select_by_policy (inode, this,
local->readable);
if (read_subvol == -1) {
local->op_ret = -1;
local->op_errno = 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:
local->readfn (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,
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;
int read_subvol = -1;
int event_generation = 0;
int ret = -1;
priv = this->private;
local = frame->local;
afr_read_txn_wipe (frame, this);
local->readfn = readfn;
local->inode = inode_ref (inode);
local->transaction.type = type;
ret = afr_inode_read_subvol_type_get (inode, this, local->readable,
&event_generation, type);
if (ret == -1)
/* very first transaction on this inode */
goto refresh;
if (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);
if (read_subvol < 0 || read_subvol > priv->child_count) {
gf_msg (this->name, GF_LOG_WARNING, 0, AFR_MSG_SPLIT_BRAIN,
"Unreadable subvolume %d found with event generation "
"%d. (Possible split-brain)",
read_subvol, event_generation);
goto refresh;
}
if (!local->child_up[read_subvol]) {
/* should never happen, just in case */
gf_log (this->name, GF_LOG_WARNING, "subvolume %d is the "
"read subvolume in this generation, but is not up",
read_subvol);
goto refresh;
}
local->read_attempted[read_subvol] = 1;
local->readfn (frame, this, read_subvol);
return 0;
refresh:
afr_inode_refresh (frame, this, inode, afr_read_txn_refresh_done);
return 0;
}
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