diff options
Diffstat (limited to 'fs/xfs/xfs_log_cil.c')
| -rw-r--r-- | fs/xfs/xfs_log_cil.c | 1201 |
1 files changed, 1201 insertions, 0 deletions
diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c new file mode 100644 index 000000000..d3884e08b --- /dev/null +++ b/fs/xfs/xfs_log_cil.c @@ -0,0 +1,1201 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (c) 2010 Red Hat, Inc. All Rights Reserved. + */ + +#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 *lip; + + list_for_each_entry(lip, &tp->t_items, li_trans) { + 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 (!test_bit(XFS_LI_DIRTY, &lip->li_flags)) + 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_large(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 *lip; + + + /* Bail out if we didn't find a log item. */ + if (list_empty(&tp->t_items)) { + ASSERT(0); + return; + } + + list_for_each_entry(lip, &tp->t_items, li_trans) { + 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 (!test_bit(XFS_LI_DIRTY, &lip->li_flags)) + 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 *lip; + 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(lip, &tp->t_items, li_trans) { + + /* Skip items which aren't dirty in this transaction. */ + if (!test_bit(XFS_LI_DIRTY, &lip->li_flags)) + 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(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); + tp->t_ticket = NULL; + 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); +} + |