/*
* 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
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* 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_format.h"
#include "xfs_log_format.h"
#include "xfs_shared.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_error.h"
#include "xfs_alloc.h"
#include "xfs_extent_busy.h"
#include "xfs_discard.h"
#include "xfs_trans.h"
#include "xfs_trans_priv.h"
#include "xfs_log.h"
#include "xfs_log_priv.h"
#include "xfs_trace.h"
struct workqueue_struct *xfs_discard_wq;
/*
* 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 *
xlog_cil_ticket_alloc(
struct xlog *log)
{
struct xlog_ticket *tic;
tic = xlog_ticket_alloc(log, 0, 1, XFS_TRANSACTION, 0,
KM_SLEEP|KM_NOFS);
/*
* 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.
*/
void
xlog_cil_init_post_recovery(
struct xlog *log)
{
log->l_cilp->xc_ctx->ticket = xlog_cil_ticket_alloc(log);
log->l_cilp->xc_ctx->sequence = 1;
}
static inline int
xlog_cil_iovec_space(
uint niovecs)
{
return round_up((sizeof(struct xfs_log_vec) +
niovecs * sizeof(struct xfs_log_iovec)),
sizeof(uint64_t));
}
/*
* Allocate or pin log vector buffers for CIL insertion.
*
* The CIL currently uses disposable buffers for copying a snapshot of the
* modified items into the log during a push. The biggest problem with this is
* the requirement to allocate the disposable buffer during the commit if:
* a) does not exist; or
* b) it is too small
*
* If we do this allocation within xlog_cil_insert_format_items(), it is done
* under the xc_ctx_lock, which means that a CIL push cannot occur during
* the memory allocation. This means that we have a potential deadlock situation
* under low memory conditions when we have lots of dirty metadata pinned in
* the CIL and we need a CIL commit to occur to free memory.
*
* To avoid this, we need to move the memory allocation outside the
* xc_ctx_lock, but because the log vector buffers are disposable, that opens
* up a TOCTOU race condition w.r.t. the CIL committing and removing the log
* vector buffers between the check and the formatting of the item into the
* log vector buffer within the xc_ctx_lock.
*
* Because the log vector buffer needs to be unchanged during the CIL push
* process, we cannot share the buffer between the transaction commit (which
* modifies the buffer) and the CIL push context that is writing the changes
* into the log. This means skipping preallocation of buffer space is
* unreliable, but we most definitely do not want to be allocating and freeing
* buffers unnecessarily during commits when overwrites can be done safely.
*
* The simplest solution to this problem is to allocate a shadow buffer when a
* log item is committed for the second time, and then to only use this buffer
* if necessary. The buffer can remain attached to the log item until such time
* it is needed, and this is the buffer that is reallocated to match the size of
* the incoming modification. Then during the formatting of the item we can swap
* the active buffer with the new one if we can't reuse the existing buffer. We
* don't free the old buffer as it may be reused on the next modification if
* it's size is right, otherwise we'll free and reallocate it at that point.
*
* 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 attaches the vector to the log item in preparation
* for the formatting step which occurs under the xc_ctx_lock.
*
* While this means the memory footprint goes up, it avoids the repeated
* alloc/free pattern that repeated modifications of an item would otherwise
* cause, and hence minimises the CPU overhead of such behaviour.
*/
static void
xlog_cil_alloc_shadow_bufs(
struct xlog *log,
struct xfs_trans *tp)
{
struct xfs_log_item_desc *lidp;
list_for_each_entry(lidp, &tp->t_items, lid_trans) {
struct xfs_log_item *lip = lidp->lid_item;
struct xfs_log_vec *lv;
int niovecs = 0;
int nbytes = 0;
int buf_size;
bool ordered = false;
/* Skip items which aren't dirty in this transaction. */
if (!(lidp->lid_flags & XFS_LID_DIRTY))
continue;
/* get number of vecs and size of data to be stored */
lip->li_ops->iop_size(lip, &niovecs, &nbytes);
/*
* Ordered items need to be tracked but we do not wish to write
* them. We need a logvec to track the object, but we do not
* need an iovec or buffer to be allocated for copying data.
*/
if (niovecs == XFS_LOG_VEC_ORDERED) {
ordered = true;
niovecs = 0;
nbytes = 0;
}
/*
* We 64-bit align the length of each iovec so that the start
* of the next one is naturally aligned. We'll need to
* account for that slack space here. Then round nbytes up
* to 64-bit alignment so that the initial buffer alignment is
* easy to calculate and verify.
*/
nbytes += niovecs * sizeof(uint64_t);
nbytes = round_up(nbytes, sizeof(uint64_t));
/*
* The data buffer needs to start 64-bit aligned, so round up
* that space to ensure we can align it appropriately and not
* overrun the buffer.
*/
buf_size = nbytes + xlog_cil_iovec_space(niovecs);
/*
* if we have no shadow buffer, or it is too small, we need to
* reallocate it.
*/
if (!lip->li_lv_shadow ||
buf_size > lip->li_lv_shadow->lv_size) {
/*
* We free and allocate here as a realloc would copy
* unecessary data. We don't use kmem_zalloc() for the
* same reason - we don't need to zero the data area in
* the buffer, only the log vector header and the iovec
* storage.
*/
kmem_free(lip->li_lv_shadow);
lv = kmem_alloc(buf_size, KM_SLEEP|KM_NOFS);
memset(lv, 0, xlog_cil_iovec_space(niovecs));
lv->lv_item = lip;
lv->lv_size = buf_size;
if (ordered)
lv->lv_buf_len = XFS_LOG_VEC_ORDERED;
else
lv->lv_iovecp = (struct xfs_log_iovec *)&lv[1];
lip->li_lv_shadow = lv;
} else {
/* same or smaller, optimise common overwrite case */
lv = lip->li_lv_shadow;
if (ordered)
lv->lv_buf_len = XFS_LOG_VEC_ORDERED;
else
lv->lv_buf_len = 0;
lv->lv_bytes = 0;
lv->lv_next = NULL;
}
/* Ensure the lv is set up according to ->iop_size */
lv->lv_niovecs = niovecs;
/* The allocated data region lies beyond the iovec region */
lv->lv_buf = (char *)lv + xlog_cil_iovec_space(niovecs);
}
}
/*
* 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.
*/
STATIC void
xfs_cil_prepare_item(
struct xlog *log,
struct xfs_log_vec *lv,
struct xfs_log_vec *old_lv,
int *diff_len,
int *diff_iovecs)
{
/* Account for the new LV being passed in */
if (lv->lv_buf_len != XFS_LOG_VEC_ORDERED) {
*diff_len += lv->lv_bytes;
*diff_iovecs += lv->lv_niovecs;
}
/*
* If there is no old LV, this is the first time we've seen the item in
* this CIL context and so we need to pin it. If we are replacing the
* old_lv, then remove the space it accounts for and make it the shadow
* buffer for later freeing. In both cases we are now switching to the
* shadow buffer, so update the the pointer to it appropriately.
*/
if (!old_lv) {
lv->lv_item->li_ops->iop_pin(lv->lv_item);
lv->lv_item->li_lv_shadow = NULL;
} else if (old_lv != lv) {
ASSERT(lv->lv_buf_len != XFS_LOG_VEC_ORDERED);
*diff_len -= old_lv->lv_bytes;
*diff_iovecs -= old_lv->lv_niovecs;
lv->lv_item->li_lv_shadow = old_lv;
}
/* 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;
}
/*
* 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 takes the prepared log vectors attached to each log item, and
* formats the changes into the log vector buffer. The buffer it uses is
* dependent on the current state of the vector in the CIL - the shadow lv is
* guaranteed to be large enough for the current modification, but we will only
* use that if we can't reuse the existing lv. If we can't reuse the existing
* lv, then simple swap it out for the shadow lv. We don't free it - that is
* done lazily either by th enext modification or the freeing of the log item.
*
* 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 void
xlog_cil_insert_format_items(
struct xlog *log,
struct xfs_trans *tp,
int *diff_len,
int *diff_iovecs)
{
struct xfs_log_item_desc *lidp;
/* Bail out if we didn't find a log item. */
if (list_empty(&tp->t_items)) {
ASSERT(0);
return;
}
list_for_each_entry(lidp, &tp->t_items, lid_trans) {
struct xfs_log_item *lip = lidp->lid_item;
struct xfs_log_vec *lv;
struct xfs_log_vec *old_lv = NULL;
struct xfs_log_vec *shadow;
bool ordered = false;
/* Skip items which aren't dirty in this transaction. */
if (!(lidp->lid_flags & XFS_LID_DIRTY))
continue;
/*
* The formatting size information is already attached to
* the shadow lv on the log item.
*/
shadow = lip->li_lv_shadow;
if (shadow->lv_buf_len == XFS_LOG_VEC_ORDERED)
ordered = true;
/* Skip items that do not have any vectors for writing */
if (!shadow->lv_niovecs && !ordered)
continue;
/* compare to existing item size */
old_lv = lip->li_lv;
if (lip->li_lv && shadow->lv_size <= lip->li_lv->lv_size) {
/* same or smaller, optimise common overwrite case */
lv = lip->li_lv;
lv->lv_next = NULL;
if (ordered)
goto insert;
/*
* set the item up as though it is a new insertion so
* that the space reservation accounting is correct.
*/
*diff_iovecs -= lv->lv_niovecs;
*diff_len -= lv->lv_bytes;
/* Ensure the lv is set up according to ->iop_size */
lv->lv_niovecs = shadow->lv_niovecs;
/* reset the lv buffer information for new formatting */
lv->lv_buf_len = 0;
lv->lv_bytes = 0;
lv->lv_buf = (char *)lv +
xlog_cil_iovec_space(lv->lv_niovecs);
} else {
/* switch to shadow buffer! */
lv = shadow;
lv->lv_item = lip;
if (ordered) {
/* track as an ordered logvec */
ASSERT(lip->li_lv == NULL);
goto insert;
}
}
ASSERT(IS_ALIGNED((unsigned long)lv->lv_buf, sizeof(uint64_t)));
lip->li_ops->iop_format(lip, lv);
insert:
xfs_cil_prepare_item(log, lv, old_lv, diff_len, diff_iovecs);
}
}
/*
* 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
xlog_cil_insert_items(
struct xlog *log,
struct xfs_trans *tp)
{
struct xfs_cil *cil = log->l_cilp;
struct xfs_cil_ctx *ctx = cil->xc_ctx;
struct xfs_log_item_desc *lidp;
int len = 0;
int diff_iovecs = 0;
int iclog_space;
int iovhdr_res = 0, split_res = 0, ctx_res = 0;
ASSERT(tp);
/*
* 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.
*/
xlog_cil_insert_format_items(log, tp, &len, &diff_iovecs);
spin_lock(&cil->xc_cil_lock);
/* account for space used by new iovec headers */
iovhdr_res = diff_iovecs * sizeof(xlog_op_header_t);
len += iovhdr_res;
ctx->nvecs += diff_iovecs;
/* attach the transaction to the CIL if it has any busy extents */
if (!list_empty(&tp->t_busy))
list_splice_init(&tp->t_busy, &ctx->busy_extents);
/*
* 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) {
ctx_res = ctx->ticket->t_unit_res;
ctx->ticket->t_curr_res = ctx_res;
tp->t_ticket->t_curr_res -= ctx_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)) {
split_res = (len + iclog_space - 1) / iclog_space;
/* need to take into account split region headers, too */
split_res *= log->l_iclog_hsize + sizeof(struct xlog_op_header);
ctx->ticket->t_unit_res += split_res;
ctx->ticket->t_curr_res += split_res;
tp->t_ticket->t_curr_res -= split_res;
ASSERT(tp->t_ticket->t_curr_res >= len);
}
tp->t_ticket->t_curr_res -= len;
ctx->space_used += len;
/*
* If we've overrun the reservation, dump the tx details before we move
* the log items. Shutdown is imminent...
*/
if (WARN_ON(tp->t_ticket->t_curr_res < 0)) {
xfs_warn(log->l_mp, "Transaction log reservation overrun:");
xfs_warn(log->l_mp,
" log items: %d bytes (iov hdrs: %d bytes)",
len, iovhdr_res);
xfs_warn(log->l_mp, " split region headers: %d bytes",
split_res);
xfs_warn(log->l_mp, " ctx ticket: %d bytes", ctx_res);
xlog_print_trans(tp);
}
/*
* Now (re-)position everything modified at the tail of the CIL.
* We do this here so we only need to take the CIL lock once during
* the transaction commit.
*/
list_for_each_entry(lidp, &tp->t_items, lid_trans) {
struct xfs_log_item *lip = lidp->lid_item;
/* Skip items which aren't dirty in this transaction. */
if (!(lidp->lid_flags & XFS_LID_DIRTY))
continue;
/*
* Only move the item if it isn't already at the tail. This is
* to prevent a transient list_empty() state when reinserting
* an item that is already the only item in the CIL.
*/
if (!list_is_last(&lip->li_cil, &cil->xc_cil))
list_move_tail(&lip->li_cil, &cil->xc_cil);
}
spin_unlock(&cil->xc_cil_lock);
if (tp->t_ticket->t_curr_res < 0)
xfs_force_shutdown(log->l_mp, SHUTDOWN_LOG_IO_ERROR);
}
static void
xlog_cil_free_logvec(
struct xfs_log_vec *log_vector)
{
struct xfs_log_vec *lv;
for (lv = log_vector; lv; ) {
struct xfs_log_vec *next = lv->lv_next;
kmem_free(lv);
lv = next;
}
}
static void
xlog_discard_endio_work(
struct work_struct *work)
{
struct xfs_cil_ctx *ctx =
container_of(work, struct xfs_cil_ctx, discard_endio_work);
struct xfs_mount *mp = ctx->cil->xc_log->l_mp;
xfs_extent_busy_clear(mp, &ctx->busy_extents, false);
kmem_free(ctx);
}
/*
* Queue up the actual completion to a thread to avoid IRQ-safe locking for
* pagb_lock. Note that we need a unbounded workqueue, otherwise we might
* get the execution delayed up to 30 seconds for weird reasons.
*/
static void
xlog_discard_endio(
struct bio *bio)
{
struct xfs_cil_ctx *ctx = bio->bi_private;
INIT_WORK(&ctx->discard_endio_work, xlog_discard_endio_work);
queue_work(xfs_discard_wq, &ctx->discard_endio_work);
bio_put(bio);
}
static void
xlog_discard_busy_extents(
struct xfs_mount *mp,
struct xfs_cil_ctx *ctx)
{
struct list_head *list = &ctx->busy_extents;
struct xfs_extent_busy *busyp;
struct bio *bio = NULL;
struct blk_plug plug;
int error = 0;
ASSERT(mp->m_flags & XFS_MOUNT_DISCARD);
blk_start_plug(&plug);
list_for_each_entry(busyp, list, list) {
trace_xfs_discard_extent(mp, busyp->agno, busyp->bno,
busyp->length);
error = __blkdev_issue_discard(mp->m_ddev_targp->bt_bdev,
XFS_AGB_TO_DADDR(mp, busyp->agno, busyp->bno),
XFS_FSB_TO_BB(mp, busyp->length),
GFP_NOFS, 0, &bio);
if (error && error != -EOPNOTSUPP) {
xfs_info(mp,
"discard failed for extent [0x%llx,%u], error %d",
(unsigned long long)busyp->bno,
busyp->length,
error);
break;
}
}
if (bio) {
bio->bi_private = ctx;
bio->bi_end_io = xlog_discard_endio;
submit_bio(bio);
} else {
xlog_discard_endio_work(&ctx->discard_endio_work);
}
blk_finish_plug(&plug);
}
/*
* 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
xlog_cil_committed(
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_extent_busy_sort(&ctx->busy_extents);
xfs_extent_busy_clear(mp, &ctx->busy_extents,
(mp->m_flags & XFS_MOUNT_DISCARD) && !abort);
/*
* If we are aborting the commit, wake up anyone waiting on the
* committing list. If we don't, then a shutdown we can leave processes
* waiting in xlog_cil_force_lsn() waiting on a sequence commit that
* will never happen because we aborted it.
*/
spin_lock(&ctx->cil->xc_push_lock);
if (abort)
wake_up_all(&ctx->cil->xc_commit_wait);
list_del(&ctx->committing);
spin_unlock(&ctx->cil->xc_push_lock);
xlog_cil_free_logvec(ctx->lv_chain);
if (!list_empty(&ctx->busy_extents))
xlog_discard_busy_extents(mp, ctx);
else
kmem_free(ctx);
}
/*
* 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.
*/
STATIC int
xlog_cil_push(
struct xlog *log)
{
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_iovecs;
int error = 0;
struct xfs_trans_header thdr;
struct xfs_log_iovec lhdr;
struct xfs_log_vec lvhdr = { NULL };
xfs_lsn_t commit_lsn;
xfs_lsn_t push_seq;
if (!cil)
return 0;
new_ctx = kmem_zalloc(sizeof(*new_ctx), KM_SLEEP|KM_NOFS);
new_ctx->ticket = xlog_cil_ticket_alloc(log);
down_write(&cil->xc_ctx_lock);
ctx = cil->xc_ctx;
spin_lock(&cil->xc_push_lock);
push_seq = cil->xc_push_seq;
ASSERT(push_seq <= ctx->sequence);
/*
* Check if we've anything to push. If there is nothing, then we don't
* move on to a new sequence number and so we have to be able to push
* this sequence again later.
*/
if (list_empty(&cil->xc_cil)) {
cil->xc_push_seq = 0;
spin_unlock(&cil->xc_push_lock);
goto out_skip;
}
/* check for a previously pushed seqeunce */
if (push_seq < cil->xc_ctx->sequence) {
spin_unlock(&cil->xc_push_lock);
goto out_skip;
}
/*
* We are now going to push this context, so add it to the committing
* list before we do anything else. This ensures that anyone waiting on
* this push can easily detect the difference between a "push in
* progress" and "CIL is empty, nothing to do".
*
* IOWs, a wait loop can now check for:
* the current sequence not being found on the committing list;
* an empty CIL; and
* an unchanged sequence number
* to detect a push that had nothing to do and therefore does not need
* waiting on. If the CIL is not empty, we get put on the committing
* list before emptying the CIL and bumping the sequence number. Hence
* an empty CIL and an unchanged sequence number means we jumped out
* above after doing nothing.
*
* Hence the waiter will either find the commit sequence on the
* committing list or the sequence number will be unchanged and the CIL
* still dirty. In that latter case, the push has not yet started, and
* so the waiter will have to continue trying to check the CIL
* committing list until it is found. In extreme cases of delay, the
* sequence may fully commit between the attempts the wait makes to wait
* on the commit sequence.
*/
list_add(&ctx->committing, &cil->xc_committing);
spin_unlock(&cil->xc_push_lock);
/*
* 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_iovecs = 0;
while (!list_empty(&cil->xc_cil)) {
struct xfs_log_item *item;
item = list_first_entry(&cil->xc_cil,
struct xfs_log_item, li_cil);
list_del_init(&item->li_cil);
if (!ctx->lv_chain)
ctx->lv_chain = item->li_lv;
else
lv->lv_next = item->li_lv;
lv = item->li_lv;
item->li_lv = NULL;
num_iovecs += lv->lv_niovecs;
}
/*
* 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.
*/
INIT_LIST_HEAD(&new_ctx->committing);
INIT_LIST_HEAD(&new_ctx->busy_extents);
new_ctx->sequence = ctx->sequence + 1;
new_ctx->cil = cil;
cil->xc_ctx = new_ctx;
/*
* 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.
*
* xfs_log_force_lsn requires us to mirror the new sequence into the cil
* structure atomically with the addition of this sequence to the
* committing list. This also ensures that we can do unlocked checks
* against the current sequence in log forces without risking
* deferencing a freed context pointer.
*/
spin_lock(&cil->xc_push_lock);
cil->xc_current_sequence = new_ctx->sequence;
spin_unlock(&cil->xc_push_lock);
up_write(&cil->xc_ctx_lock);
/*
* 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);
lhdr.i_type = XLOG_REG_TYPE_TRANSHDR;
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.
*/
restart:
spin_lock(&cil->xc_push_lock);
list_for_each_entry(new_ctx, &cil->xc_committing, committing) {
/*
* Avoid getting stuck in this loop because we were woken by the
* shutdown, but then went back to sleep once already in the
* shutdown state.
*/
if (XLOG_FORCED_SHUTDOWN(log)) {
spin_unlock(&cil->xc_push_lock);
goto out_abort_free_ticket;
}
/*
* Higher sequences will wait for this one so skip them.
* Don't wait for our own sequence, either.
*/
if (new_ctx->sequence >= ctx->sequence)
continue;
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_push_lock);
goto restart;
}
}
spin_unlock(&cil->xc_push_lock);
/* xfs_log_done always frees the ticket on error. */
commit_lsn = xfs_log_done(log->l_mp, tic, &commit_iclog, false);
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.
*/
spin_lock(&cil->xc_push_lock);
ctx->commit_lsn = commit_lsn;
wake_up_all(&cil->xc_commit_wait);
spin_unlock(&cil->xc_push_lock);
/* release the hounds! */
return xfs_log_release_iclog(log->l_mp, commit_iclog);
out_skip:
up_write(&cil->xc_ctx_lock);
xfs_log_ticket_put(new_ctx->ticket);
kmem_free(new_ctx);
return 0;
out_abort_free_ticket:
xfs_log_ticket_put(tic);
out_abort:
xlog_cil_committed(ctx, XFS_LI_ABORTED);
return -EIO;
}
static void
xlog_cil_push_work(
struct work_struct *work)
{
struct xfs_cil *cil = container_of(work, struct xfs_cil,
xc_push_work);
xlog_cil_push(cil->xc_log);
}
/*
* 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.
*/
static void
xlog_cil_push_background(
struct xlog *log)
{
struct xfs_cil *cil = log->l_cilp;
/*
* The cil won't be empty because we are called while holding the
* context lock so whatever we added to the CIL will still be there
*/
ASSERT(!list_empty(&cil->xc_cil));
/*
* don't do a background push if we haven't used up all the
* space available yet.
*/
if (cil->xc_ctx->space_used < XLOG_CIL_SPACE_LIMIT(log))
return;
spin_lock(&cil->xc_push_lock);
if (cil->xc_push_seq < cil->xc_current_sequence) {
cil->xc_push_seq = cil->xc_current_sequence;
queue_work(log->l_mp->m_cil_workqueue, &cil->xc_push_work);
}
spin_unlock(&cil->xc_push_lock);
}
/*
* xlog_cil_push_now() is used to trigger an immediate CIL push to the sequence
* number that is passed. When it returns, the work will be queued for
* @push_seq, but it won't be completed. The caller is expected to do any
* waiting for push_seq to complete if it is required.
*/
static void
xlog_cil_push_now(
struct xlog *log,
xfs_lsn_t push_seq)
{
struct xfs_cil *cil = log->l_cilp;
if (!cil)
return;
ASSERT(push_seq && push_seq <= cil->xc_current_sequence);
/* start on any pending background push to minimise wait time on it */
flush_work(&cil->xc_push_work);
/*
* If the CIL is empty or we've already pushed the sequence then
* there's no work we need to do.
*/
spin_lock(&cil->xc_push_lock);
if (list_empty(&cil->xc_cil) || push_seq <= cil->xc_push_seq) {
spin_unlock(&cil->xc_push_lock);
return;
}
cil->xc_push_seq = push_seq;
queue_work(log->l_mp->m_cil_workqueue, &cil->xc_push_work);
spin_unlock(&cil->xc_push_lock);
}
bool
xlog_cil_empty(
struct xlog *log)
{
struct xfs_cil *cil = log->l_cilp;
bool empty = false;
spin_lock(&cil->xc_push_lock);
if (list_empty(&cil->xc_cil))
empty = true;
spin_unlock(&cil->xc_push_lock);
return empty;
}
/*
* 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.
*
* 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.
*/
void
xfs_log_commit_cil(
struct xfs_mount *mp,
struct xfs_trans *tp,
xfs_lsn_t *commit_lsn,
bool regrant)
{
struct xlog *log = mp->m_log;
struct xfs_cil *cil = log->l_cilp;
xfs_lsn_t xc_commit_lsn;
/*
* Do all necessary memory allocation before we lock the CIL.
* This ensures the allocation does not deadlock with a CIL
* push in memory reclaim (e.g. from kswapd).
*/
xlog_cil_alloc_shadow_bufs(log, tp);
/* lock out background commit */
down_read(&cil->xc_ctx_lock);
xlog_cil_insert_items(log, tp);
xc_commit_lsn = cil->xc_ctx->sequence;
if (commit_lsn)
*commit_lsn = xc_commit_lsn;
xfs_log_done(mp, tp->t_ticket, NULL, regrant);
xfs_trans_unreserve_and_mod_sb(tp);
/*
* 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, xc_commit_lsn, false);
xlog_cil_push_background(log);
up_read(&cil->xc_ctx_lock);
}
/*
* 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.
*/
xfs_lsn_t
xlog_cil_force_lsn(
struct xlog *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.
*/
restart:
xlog_cil_push_now(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.
*/
spin_lock(&cil->xc_push_lock);
list_for_each_entry(ctx, &cil->xc_committing, committing) {
/*
* Avoid getting stuck in this loop because we were woken by the
* shutdown, but then went back to sleep once already in the
* shutdown state.
*/
if (XLOG_FORCED_SHUTDOWN(log))
goto out_shutdown;
if (ctx->sequence > sequence)
continue;
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_push_lock);
goto restart;
}
if (ctx->sequence != sequence)
continue;
/* found it! */
commit_lsn = ctx->commit_lsn;
}
/*
* The call to xlog_cil_push_now() executes the push in the background.
* Hence by the time we have got here it our sequence may not have been
* pushed yet. This is true if the current sequence still matches the
* push sequence after the above wait loop and the CIL still contains
* dirty objects. This is guaranteed by the push code first adding the
* context to the committing list before emptying the CIL.
*
* Hence if we don't find the context in the committing list and the
* current sequence number is unchanged then the CIL contents are
* significant. If the CIL is empty, if means there was nothing to push
* and that means there is nothing to wait for. If the CIL is not empty,
* it means we haven't yet started the push, because if it had started
* we would have found the context on the committing list.
*/
if (sequence == cil->xc_current_sequence &&
!list_empty(&cil->xc_cil)) {
spin_unlock(&cil->xc_push_lock);
goto restart;
}
spin_unlock(&cil->xc_push_lock);
return commit_lsn;
/*
* We detected a shutdown in progress. We need to trigger the log force
* to pass through it's iclog state machine error handling, even though
* we are already in a shutdown state. Hence we can't return
* NULLCOMMITLSN here as that has special meaning to log forces (i.e.
* LSN is already stable), so we return a zero LSN instead.
*/
out_shutdown:
spin_unlock(&cil->xc_push_lock);
return 0;
}
/*
* 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.
*/
bool
xfs_log_item_in_current_chkpt(
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;
}
/*
* Perform initial CIL structure initialisation.
*/
int
xlog_cil_init(
struct xlog *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) {
kmem_free(cil);
return -ENOMEM;
}
INIT_WORK(&cil->xc_push_work, xlog_cil_push_work);
INIT_LIST_HEAD(&cil->xc_cil);
INIT_LIST_HEAD(&cil->xc_committing);
spin_lock_init(&cil->xc_cil_lock);
spin_lock_init(&cil->xc_push_lock);
init_rwsem(&cil->xc_ctx_lock);
init_waitqueue_head(&cil->xc_commit_wait);
INIT_LIST_HEAD(&ctx->committing);
INIT_LIST_HEAD(&ctx->busy_extents);
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;
}
void
xlog_cil_destroy(
struct xlog *log)
{
if (log->l_cilp->xc_ctx) {
if (log->l_cilp->xc_ctx->ticket)
xfs_log_ticket_put(log->l_cilp->xc_ctx->ticket);
kmem_free(log->l_cilp->xc_ctx);
}
ASSERT(list_empty(&log->l_cilp->xc_cil));
kmem_free(log->l_cilp);
}
