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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"
#include "afr-messages.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;
}
#define AFR_READ_TXN_SET_ERROR_AND_GOTO(ret, errnum, index, label) \
do { \
local->op_ret = ret; \
local->op_errno = errnum; \
read_subvol = index; \
gf_msg (this->name, GF_LOG_ERROR, EIO, AFR_MSG_SPLIT_BRAIN,\
"Failing %s on gfid %s: split-brain observed.",\
gf_fop_list[local->op], uuid_utoa (inode->gfid));\
goto label; \
} while (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;
int spb_choice = -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_get_readable (frame, inode, this, local->readable,
&event_generation,
local->transaction.type);
if (ret == -EIO || !event_generation)
/* Even after refresh, we don't have a good
read subvolume. Time to bail */
AFR_READ_TXN_SET_ERROR_AND_GOTO (-1, EIO, -1, readfn);
read_subvol = afr_read_subvol_select_by_policy (inode, this,
local->readable, NULL);
if (read_subvol == -1)
AFR_READ_TXN_SET_ERROR_AND_GOTO (-1, EIO, -1, 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_inode_split_brain_choice_get (inode, this,
&spb_choice);
if ((ret == 0) && spb_choice >= 0)
read_subvol = spb_choice;
}
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, 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);
if (priv->quorum_reads &&
priv->quorum_count && !afr_has_quorum (priv->child_up, this)) {
local->op_ret = -1;
local->op_errno = ENOTCONN;
read_subvol = -1;
goto read;
}
if (!afr_is_consistent_io_possible (local, priv, &local->op_errno)) {
local->op_ret = -1;
read_subvol = -1;
goto read;
}
local->transaction.type = type;
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 (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 (this->name, GF_LOG_WARNING, 0, AFR_MSG_SPLIT_BRAIN,
"Unreadable subvolume %d found with event generation "
"%d for gfid %s. (Possible split-brain)",
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:
local->readfn (frame, this, read_subvol);
return 0;
refresh:
afr_inode_refresh (frame, this, inode, NULL, afr_read_txn_refresh_done);
return 0;
}
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