blob: d4fadbe8ac90d732d6eca14b735eeb22a3e90f12 [file] [log] [blame]
* Copyright (c) 2010 Red Hat, Inc. All Rights Reserved.
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation.
* This program is distributed in the hope that it would be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_types.h"
#include "xfs_bit.h"
#include "xfs_log.h"
#include "xfs_inum.h"
#include "xfs_trans.h"
#include "xfs_trans_priv.h"
#include "xfs_log_priv.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_error.h"
#include "xfs_alloc.h"
#include "xfs_discard.h"
* Perform initial CIL structure initialisation.
struct log *log)
struct xfs_cil *cil;
struct xfs_cil_ctx *ctx;
cil = kmem_zalloc(sizeof(*cil), KM_SLEEP|KM_MAYFAIL);
if (!cil)
return ENOMEM;
ctx = kmem_zalloc(sizeof(*ctx), KM_SLEEP|KM_MAYFAIL);
if (!ctx) {
return ENOMEM;
ctx->sequence = 1;
ctx->cil = cil;
cil->xc_ctx = ctx;
cil->xc_current_sequence = ctx->sequence;
cil->xc_log = log;
log->l_cilp = cil;
return 0;
struct log *log)
if (log->l_cilp->xc_ctx) {
if (log->l_cilp->xc_ctx->ticket)
* Allocate a new ticket. Failing to get a new ticket makes it really hard to
* recover, so we don't allow failure here. Also, we allocate in a context that
* we don't want to be issuing transactions from, so we need to tell the
* allocation code this as well.
* We don't reserve any space for the ticket - we are going to steal whatever
* space we require from transactions as they commit. To ensure we reserve all
* the space required, we need to set the current reservation of the ticket to
* zero so that we know to steal the initial transaction overhead from the
* first transaction commit.
static struct xlog_ticket *
struct log *log)
struct xlog_ticket *tic;
tic = xlog_ticket_alloc(log, 0, 1, XFS_TRANSACTION, 0,
tic->t_trans_type = XFS_TRANS_CHECKPOINT;
* set the current reservation to zero so we know to steal the basic
* transaction overhead reservation from the first transaction commit.
tic->t_curr_res = 0;
return tic;
* After the first stage of log recovery is done, we know where the head and
* tail of the log are. We need this log initialisation done before we can
* initialise the first CIL checkpoint context.
* Here we allocate a log ticket to track space usage during a CIL push. This
* ticket is passed to xlog_write() directly so that we don't slowly leak log
* space by failing to account for space used by log headers and additional
* region headers for split regions.
struct log *log)
log->l_cilp->xc_ctx->ticket = xlog_cil_ticket_alloc(log);
log->l_cilp->xc_ctx->sequence = 1;
log->l_cilp->xc_ctx->commit_lsn = xlog_assign_lsn(log->l_curr_cycle,
* Format log item into a flat buffers
* For delayed logging, we need to hold a formatted buffer containing all the
* changes on the log item. This enables us to relog the item in memory and
* write it out asynchronously without needing to relock the object that was
* modified at the time it gets written into the iclog.
* This function builds a vector for the changes in each log item in the
* transaction. It then works out the length of the buffer needed for each log
* item, allocates them and formats the vector for the item into the buffer.
* The buffer is then attached to the log item are then inserted into the
* Committed Item List for tracking until the next checkpoint is written out.
* We don't set up region headers during this process; we simply copy the
* regions into the flat buffer. We can do this because we still have to do a
* formatting step to write the regions into the iclog buffer. Writing the
* ophdrs during the iclog write means that we can support splitting large
* regions across iclog boundares without needing a change in the format of the
* item/region encapsulation.
* Hence what we need to do now is change the rewrite the vector array to point
* to the copied region inside the buffer we just allocated. This allows us to
* format the regions into the iclog as though they are being formatted
* directly out of the objects themselves.
static struct xfs_log_vec *
struct xfs_trans *tp)
struct xfs_log_item_desc *lidp;
struct xfs_log_vec *lv = NULL;
struct xfs_log_vec *ret_lv = NULL;
/* Bail out if we didn't find a log item. */
if (list_empty(&tp->t_items)) {
return NULL;
list_for_each_entry(lidp, &tp->t_items, lid_trans) {
struct xfs_log_vec *new_lv;
void *ptr;
int index;
int len = 0;
uint niovecs;
/* Skip items which aren't dirty in this transaction. */
if (!(lidp->lid_flags & XFS_LID_DIRTY))
/* Skip items that do not have any vectors for writing */
niovecs = IOP_SIZE(lidp->lid_item);
if (!niovecs)
new_lv = kmem_zalloc(sizeof(*new_lv) +
niovecs * sizeof(struct xfs_log_iovec),
/* The allocated iovec region lies beyond the log vector. */
new_lv->lv_iovecp = (struct xfs_log_iovec *)&new_lv[1];
new_lv->lv_niovecs = niovecs;
new_lv->lv_item = lidp->lid_item;
/* build the vector array and calculate it's length */
IOP_FORMAT(new_lv->lv_item, new_lv->lv_iovecp);
for (index = 0; index < new_lv->lv_niovecs; index++)
len += new_lv->lv_iovecp[index].i_len;
new_lv->lv_buf_len = len;
new_lv->lv_buf = kmem_alloc(new_lv->lv_buf_len,
ptr = new_lv->lv_buf;
for (index = 0; index < new_lv->lv_niovecs; index++) {
struct xfs_log_iovec *vec = &new_lv->lv_iovecp[index];
memcpy(ptr, vec->i_addr, vec->i_len);
vec->i_addr = ptr;
ptr += vec->i_len;
ASSERT(ptr == new_lv->lv_buf + new_lv->lv_buf_len);
if (!ret_lv)
ret_lv = new_lv;
lv->lv_next = new_lv;
lv = new_lv;
return ret_lv;
* Prepare the log item for insertion into the CIL. Calculate the difference in
* log space and vectors it will consume, and if it is a new item pin it as
* well.
struct log *log,
struct xfs_log_vec *lv,
int *len,
int *diff_iovecs)
struct xfs_log_vec *old = lv->lv_item->li_lv;
if (old) {
/* existing lv on log item, space used is a delta */
ASSERT(old->lv_buf && old->lv_buf_len && old->lv_niovecs);
*len += lv->lv_buf_len - old->lv_buf_len;
*diff_iovecs += lv->lv_niovecs - old->lv_niovecs;
} else {
/* new lv, must pin the log item */
*len += lv->lv_buf_len;
*diff_iovecs += lv->lv_niovecs;
/* attach new log vector to log item */
lv->lv_item->li_lv = lv;
* If this is the first time the item is being committed to the
* CIL, store the sequence number on the log item so we can
* tell in future commits whether this is the first checkpoint
* the item is being committed into.
if (!lv->lv_item->li_seq)
lv->lv_item->li_seq = log->l_cilp->xc_ctx->sequence;
* Insert the log items into the CIL and calculate the difference in space
* consumed by the item. Add the space to the checkpoint ticket and calculate
* if the change requires additional log metadata. If it does, take that space
* as well. Remove the amount of space we added to the checkpoint ticket from
* the current transaction ticket so that the accounting works out correctly.
static void
struct log *log,
struct xfs_log_vec *log_vector,
struct xlog_ticket *ticket)
struct xfs_cil *cil = log->l_cilp;
struct xfs_cil_ctx *ctx = cil->xc_ctx;
struct xfs_log_vec *lv;
int len = 0;
int diff_iovecs = 0;
int iclog_space;
* Do all the accounting aggregation and switching of log vectors
* around in a separate loop to the insertion of items into the CIL.
* Then we can do a separate loop to update the CIL within a single
* lock/unlock pair. This reduces the number of round trips on the CIL
* lock from O(nr_logvectors) to O(1) and greatly reduces the overall
* hold time for the transaction commit.
* If this is the first time the item is being placed into the CIL in
* this context, pin it so it can't be written to disk until the CIL is
* flushed to the iclog and the iclog written to disk.
* We can do this safely because the context can't checkpoint until we
* are done so it doesn't matter exactly how we update the CIL.
for (lv = log_vector; lv; lv = lv->lv_next)
xfs_cil_prepare_item(log, lv, &len, &diff_iovecs);
/* account for space used by new iovec headers */
len += diff_iovecs * sizeof(xlog_op_header_t);
/* move the items to the tail of the CIL */
for (lv = log_vector; lv; lv = lv->lv_next)
list_move_tail(&lv->lv_item->li_cil, &cil->xc_cil);
ctx->nvecs += diff_iovecs;
* Now transfer enough transaction reservation to the context ticket
* for the checkpoint. The context ticket is special - the unit
* reservation has to grow as well as the current reservation as we
* steal from tickets so we can correctly determine the space used
* during the transaction commit.
if (ctx->ticket->t_curr_res == 0) {
/* first commit in checkpoint, steal the header reservation */
ASSERT(ticket->t_curr_res >= ctx->ticket->t_unit_res + len);
ctx->ticket->t_curr_res = ctx->ticket->t_unit_res;
ticket->t_curr_res -= ctx->ticket->t_unit_res;
/* do we need space for more log record headers? */
iclog_space = log->l_iclog_size - log->l_iclog_hsize;
if (len > 0 && (ctx->space_used / iclog_space !=
(ctx->space_used + len) / iclog_space)) {
int hdrs;
hdrs = (len + iclog_space - 1) / iclog_space;
/* need to take into account split region headers, too */
hdrs *= log->l_iclog_hsize + sizeof(struct xlog_op_header);
ctx->ticket->t_unit_res += hdrs;
ctx->ticket->t_curr_res += hdrs;
ticket->t_curr_res -= hdrs;
ASSERT(ticket->t_curr_res >= len);
ticket->t_curr_res -= len;
ctx->space_used += len;
static void
struct xfs_log_vec *log_vector)
struct xfs_log_vec *lv;
for (lv = log_vector; lv; ) {
struct xfs_log_vec *next = lv->lv_next;
lv = next;
* Mark all items committed and clear busy extents. We free the log vector
* chains in a separate pass so that we unpin the log items as quickly as
* possible.
static void
void *args,
int abort)
struct xfs_cil_ctx *ctx = args;
struct xfs_mount *mp = ctx->cil->xc_log->l_mp;
xfs_trans_committed_bulk(ctx->cil->xc_log->l_ailp, ctx->lv_chain,
ctx->start_lsn, abort);
xfs_alloc_busy_clear(mp, &ctx->busy_extents,
(mp->m_flags & XFS_MOUNT_DISCARD) && !abort);
if (!list_empty(&ctx->busy_extents)) {
xfs_discard_extents(mp, &ctx->busy_extents);
xfs_alloc_busy_clear(mp, &ctx->busy_extents, false);
* Push the Committed Item List to the log. If @push_seq flag is zero, then it
* is a background flush and so we can chose to ignore it. Otherwise, if the
* current sequence is the same as @push_seq we need to do a flush. If
* @push_seq is less than the current sequence, then it has already been
* flushed and we don't need to do anything - the caller will wait for it to
* complete if necessary.
* @push_seq is a value rather than a flag because that allows us to do an
* unlocked check of the sequence number for a match. Hence we can allows log
* forces to run racily and not issue pushes for the same sequence twice. If we
* get a race between multiple pushes for the same sequence they will block on
* the first one and then abort, hence avoiding needless pushes.
struct log *log,
xfs_lsn_t push_seq)
struct xfs_cil *cil = log->l_cilp;
struct xfs_log_vec *lv;
struct xfs_cil_ctx *ctx;
struct xfs_cil_ctx *new_ctx;
struct xlog_in_core *commit_iclog;
struct xlog_ticket *tic;
int num_lv;
int num_iovecs;
int len;
int error = 0;
struct xfs_trans_header thdr;
struct xfs_log_iovec lhdr;
struct xfs_log_vec lvhdr = { NULL };
xfs_lsn_t commit_lsn;
if (!cil)
return 0;
ASSERT(!push_seq || push_seq <= cil->xc_ctx->sequence);
new_ctx = kmem_zalloc(sizeof(*new_ctx), KM_SLEEP|KM_NOFS);
new_ctx->ticket = xlog_cil_ticket_alloc(log);
* Lock out transaction commit, but don't block for background pushes
* unless we are well over the CIL space limit. See the definition of
* XLOG_CIL_HARD_SPACE_LIMIT() for the full explanation of the logic
* used here.
if (!down_write_trylock(&cil->xc_ctx_lock)) {
if (!push_seq &&
cil->xc_ctx->space_used < XLOG_CIL_HARD_SPACE_LIMIT(log))
goto out_free_ticket;
ctx = cil->xc_ctx;
/* check if we've anything to push */
if (list_empty(&cil->xc_cil))
goto out_skip;
/* check for spurious background flush */
if (!push_seq && cil->xc_ctx->space_used < XLOG_CIL_SPACE_LIMIT(log))
goto out_skip;
/* check for a previously pushed seqeunce */
if (push_seq && push_seq < cil->xc_ctx->sequence)
goto out_skip;
* pull all the log vectors off the items in the CIL, and
* remove the items from the CIL. We don't need the CIL lock
* here because it's only needed on the transaction commit
* side which is currently locked out by the flush lock.
lv = NULL;
num_lv = 0;
num_iovecs = 0;
len = 0;
while (!list_empty(&cil->xc_cil)) {
struct xfs_log_item *item;
int i;
item = list_first_entry(&cil->xc_cil,
struct xfs_log_item, li_cil);
if (!ctx->lv_chain)
ctx->lv_chain = item->li_lv;
lv->lv_next = item->li_lv;
lv = item->li_lv;
item->li_lv = NULL;
num_iovecs += lv->lv_niovecs;
for (i = 0; i < lv->lv_niovecs; i++)
len += lv->lv_iovecp[i].i_len;
* initialise the new context and attach it to the CIL. Then attach
* the current context to the CIL committing lsit so it can be found
* during log forces to extract the commit lsn of the sequence that
* needs to be forced.
new_ctx->sequence = ctx->sequence + 1;
new_ctx->cil = cil;
cil->xc_ctx = new_ctx;
* mirror the new sequence into the cil structure so that we can do
* unlocked checks against the current sequence in log forces without
* risking deferencing a freed context pointer.
cil->xc_current_sequence = new_ctx->sequence;
* The switch is now done, so we can drop the context lock and move out
* of a shared context. We can't just go straight to the commit record,
* though - we need to synchronise with previous and future commits so
* that the commit records are correctly ordered in the log to ensure
* that we process items during log IO completion in the correct order.
* For example, if we get an EFI in one checkpoint and the EFD in the
* next (e.g. due to log forces), we do not want the checkpoint with
* the EFD to be committed before the checkpoint with the EFI. Hence
* we must strictly order the commit records of the checkpoints so
* that: a) the checkpoint callbacks are attached to the iclogs in the
* correct order; and b) the checkpoints are replayed in correct order
* in log recovery.
* Hence we need to add this context to the committing context list so
* that higher sequences will wait for us to write out a commit record
* before they do.
list_add(&ctx->committing, &cil->xc_committing);
* Build a checkpoint transaction header and write it to the log to
* begin the transaction. We need to account for the space used by the
* transaction header here as it is not accounted for in xlog_write().
* The LSN we need to pass to the log items on transaction commit is
* the LSN reported by the first log vector write. If we use the commit
* record lsn then we can move the tail beyond the grant write head.
tic = ctx->ticket;
thdr.th_magic = XFS_TRANS_HEADER_MAGIC;
thdr.th_type = XFS_TRANS_CHECKPOINT;
thdr.th_tid = tic->t_tid;
thdr.th_num_items = num_iovecs;
lhdr.i_addr = &thdr;
lhdr.i_len = sizeof(xfs_trans_header_t);
tic->t_curr_res -= lhdr.i_len + sizeof(xlog_op_header_t);
lvhdr.lv_niovecs = 1;
lvhdr.lv_iovecp = &lhdr;
lvhdr.lv_next = ctx->lv_chain;
error = xlog_write(log, &lvhdr, tic, &ctx->start_lsn, NULL, 0);
if (error)
goto out_abort_free_ticket;
* now that we've written the checkpoint into the log, strictly
* order the commit records so replay will get them in the right order.
list_for_each_entry(new_ctx, &cil->xc_committing, committing) {
* Higher sequences will wait for this one so skip them.
* Don't wait for own own sequence, either.
if (new_ctx->sequence >= ctx->sequence)
if (!new_ctx->commit_lsn) {
* It is still being pushed! Wait for the push to
* complete, then start again from the beginning.
xlog_wait(&cil->xc_commit_wait, &cil->xc_cil_lock);
goto restart;
/* xfs_log_done always frees the ticket on error. */
commit_lsn = xfs_log_done(log->l_mp, tic, &commit_iclog, 0);
if (commit_lsn == -1)
goto out_abort;
/* attach all the transactions w/ busy extents to iclog */
ctx->log_cb.cb_func = xlog_cil_committed;
ctx->log_cb.cb_arg = ctx;
error = xfs_log_notify(log->l_mp, commit_iclog, &ctx->log_cb);
if (error)
goto out_abort;
* now the checkpoint commit is complete and we've attached the
* callbacks to the iclog we can assign the commit LSN to the context
* and wake up anyone who is waiting for the commit to complete.
ctx->commit_lsn = commit_lsn;
/* release the hounds! */
return xfs_log_release_iclog(log->l_mp, commit_iclog);
return 0;
xlog_cil_committed(ctx, XFS_LI_ABORTED);
return XFS_ERROR(EIO);
* Commit a transaction with the given vector to the Committed Item List.
* To do this, we need to format the item, pin it in memory if required and
* account for the space used by the transaction. Once we have done that we
* need to release the unused reservation for the transaction, attach the
* transaction to the checkpoint context so we carry the busy extents through
* to checkpoint completion, and then unlock all the items in the transaction.
* For more specific information about the order of operations in
* xfs_log_commit_cil() please refer to the comments in
* xfs_trans_commit_iclog().
* Called with the context lock already held in read mode to lock out
* background commit, returns without it held once background commits are
* allowed again.
struct xfs_mount *mp,
struct xfs_trans *tp,
xfs_lsn_t *commit_lsn,
int flags)
struct log *log = mp->m_log;
int log_flags = 0;
int push = 0;
struct xfs_log_vec *log_vector;
* Do all the hard work of formatting items (including memory
* allocation) outside the CIL context lock. This prevents stalling CIL
* pushes when we are low on memory and a transaction commit spends a
* lot of time in memory reclaim.
log_vector = xlog_cil_prepare_log_vecs(tp);
if (!log_vector)
return ENOMEM;
/* lock out background commit */
if (commit_lsn)
*commit_lsn = log->l_cilp->xc_ctx->sequence;
xlog_cil_insert_items(log, log_vector, tp->t_ticket);
/* check we didn't blow the reservation */
if (tp->t_ticket->t_curr_res < 0)
xlog_print_tic_res(log->l_mp, tp->t_ticket);
/* attach the transaction to the CIL if it has any busy extents */
if (!list_empty(&tp->t_busy)) {
tp->t_commit_lsn = *commit_lsn;
xfs_log_done(mp, tp->t_ticket, NULL, log_flags);
* Once all the items of the transaction have been copied to the CIL,
* the items can be unlocked and freed.
* This needs to be done before we drop the CIL context lock because we
* have to update state in the log items and unlock them before they go
* to disk. If we don't, then the CIL checkpoint can race with us and
* we can run checkpoint completion before we've updated and unlocked
* the log items. This affects (at least) processing of stale buffers,
* inodes and EFIs.
xfs_trans_free_items(tp, *commit_lsn, 0);
/* check for background commit before unlock */
if (log->l_cilp->xc_ctx->space_used > XLOG_CIL_SPACE_LIMIT(log))
push = 1;
* We need to push CIL every so often so we don't cache more than we
* can fit in the log. The limit really is that a checkpoint can't be
* more than half the log (the current checkpoint is not allowed to
* overwrite the previous checkpoint), but commit latency and memory
* usage limit this to a smaller size in most cases.
if (push)
xlog_cil_push(log, 0);
return 0;
* Conditionally push the CIL based on the sequence passed in.
* We only need to push if we haven't already pushed the sequence
* number given. Hence the only time we will trigger a push here is
* if the push sequence is the same as the current context.
* We return the current commit lsn to allow the callers to determine if a
* iclog flush is necessary following this call.
* XXX: Initially, just push the CIL unconditionally and return whatever
* commit lsn is there. It'll be empty, so this is broken for now.
struct log *log,
xfs_lsn_t sequence)
struct xfs_cil *cil = log->l_cilp;
struct xfs_cil_ctx *ctx;
xfs_lsn_t commit_lsn = NULLCOMMITLSN;
ASSERT(sequence <= cil->xc_current_sequence);
* check to see if we need to force out the current context.
* xlog_cil_push() handles racing pushes for the same sequence,
* so no need to deal with it here.
if (sequence == cil->xc_current_sequence)
xlog_cil_push(log, sequence);
* See if we can find a previous sequence still committing.
* We need to wait for all previous sequence commits to complete
* before allowing the force of push_seq to go ahead. Hence block
* on commits for those as well.
list_for_each_entry(ctx, &cil->xc_committing, committing) {
if (ctx->sequence > sequence)
if (!ctx->commit_lsn) {
* It is still being pushed! Wait for the push to
* complete, then start again from the beginning.
xlog_wait(&cil->xc_commit_wait, &cil->xc_cil_lock);
goto restart;
if (ctx->sequence != sequence)
/* found it! */
commit_lsn = ctx->commit_lsn;
return commit_lsn;
* Check if the current log item was first committed in this sequence.
* We can't rely on just the log item being in the CIL, we have to check
* the recorded commit sequence number.
* Note: for this to be used in a non-racy manner, it has to be called with
* CIL flushing locked out. As a result, it should only be used during the
* transaction commit process when deciding what to format into the item.
struct xfs_log_item *lip)
struct xfs_cil_ctx *ctx;
if (list_empty(&lip->li_cil))
return false;
ctx = lip->li_mountp->m_log->l_cilp->xc_ctx;
* li_seq is written on the first commit of a log item to record the
* first checkpoint it is written to. Hence if it is different to the
* current sequence, we're in a new checkpoint.
if (XFS_LSN_CMP(lip->li_seq, ctx->sequence) != 0)
return false;
return true;