xfs: simplify log item descriptor tracking

Currently we track log item descriptor belonging to a transaction using a
complex opencoded chunk allocator.  This code has been there since day one
and seems to work around the lack of an efficient slab allocator.

This patch replaces it with dynamically allocated log item descriptors
from a dedicated slab pool, linked to the transaction by a linked list.

This allows to greatly simplify the log item descriptor tracking to the
point where it's just a couple hundred lines in xfs_trans.c instead of
a separate file.  The external API has also been simplified while we're
at it - the xfs_trans_add_item and xfs_trans_del_item functions to add/
delete items from a transaction have been simplified to the bare minium,
and the xfs_trans_find_item function is replaced with a direct dereference
of the li_desc field.  All debug code walking the list of log items in
a transaction is down to a simple list_for_each_entry.

Note that we could easily use a singly linked list here instead of the
double linked list from list.h as the fastpath only does deletion from
sequential traversal.  But given that we don't have one available as
a library function yet I use the list.h functions for simplicity.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

1 files changed, 0 insertions, 440 deletions

diff --git a/fs/xfs/xfs_trans_item.c b/fs/xfs/xfs_trans_item.c
deleted file mode 100644
index 55035a7401cb..000000000000
--- a/fs/xfs/xfs_trans_item.c
+++ /dev/null
@@ -1,440 +0,0 @@
-/*
- * Copyright (c) 2000-2002,2005 Silicon Graphics, 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_types.h"
-#include "xfs_log.h"
-#include "xfs_inum.h"
-#include "xfs_trans.h"
-#include "xfs_trans_priv.h"
-/* XXX: from here down needed until struct xfs_trans has its own ailp */
-#include "xfs_bit.h"
-#include "xfs_buf_item.h"
-#include "xfs_sb.h"
-#include "xfs_ag.h"
-#include "xfs_dir2.h"
-#include "xfs_mount.h"
-
-STATIC int	xfs_trans_unlock_chunk(xfs_log_item_chunk_t *,
-					int, int, xfs_lsn_t);
-
-/*
- * This is called to add the given log item to the transaction's
- * list of log items.  It must find a free log item descriptor
- * or allocate a new one and add the item to that descriptor.
- * The function returns a pointer to item descriptor used to point
- * to the new item.  The log item will now point to its new descriptor
- * with its li_desc field.
- */
-xfs_log_item_desc_t *
-xfs_trans_add_item(xfs_trans_t *tp, xfs_log_item_t *lip)
-{
-	xfs_log_item_desc_t	*lidp;
-	xfs_log_item_chunk_t	*licp;
-	int			i=0;
-
-	/*
-	 * If there are no free descriptors, allocate a new chunk
-	 * of them and put it at the front of the chunk list.
-	 */
-	if (tp->t_items_free == 0) {
-		licp = (xfs_log_item_chunk_t*)
-		       kmem_alloc(sizeof(xfs_log_item_chunk_t), KM_SLEEP);
-		ASSERT(licp != NULL);
-		/*
-		 * Initialize the chunk, and then
-		 * claim the first slot in the newly allocated chunk.
-		 */
-		xfs_lic_init(licp);
-		xfs_lic_claim(licp, 0);
-		licp->lic_unused = 1;
-		xfs_lic_init_slot(licp, 0);
-		lidp = xfs_lic_slot(licp, 0);
-
-		/*
-		 * Link in the new chunk and update the free count.
-		 */
-		licp->lic_next = tp->t_items.lic_next;
-		tp->t_items.lic_next = licp;
-		tp->t_items_free = XFS_LIC_NUM_SLOTS - 1;
-
-		/*
-		 * Initialize the descriptor and the generic portion
-		 * of the log item.
-		 *
-		 * Point the new slot at this item and return it.
-		 * Also point the log item at its currently active
-		 * descriptor and set the item's mount pointer.
-		 */
-		lidp->lid_item = lip;
-		lidp->lid_flags = 0;
-		lidp->lid_size = 0;
-		lip->li_desc = lidp;
-		lip->li_mountp = tp->t_mountp;
-		lip->li_ailp = tp->t_mountp->m_ail;
-		return lidp;
-	}
-
-	/*
-	 * Find the free descriptor. It is somewhere in the chunklist
-	 * of descriptors.
-	 */
-	licp = &tp->t_items;
-	while (licp != NULL) {
-		if (xfs_lic_vacancy(licp)) {
-			if (licp->lic_unused <= XFS_LIC_MAX_SLOT) {
-				i = licp->lic_unused;
-				ASSERT(xfs_lic_isfree(licp, i));
-				break;
-			}
-			for (i = 0; i <= XFS_LIC_MAX_SLOT; i++) {
-				if (xfs_lic_isfree(licp, i))
-					break;
-			}
-			ASSERT(i <= XFS_LIC_MAX_SLOT);
-			break;
-		}
-		licp = licp->lic_next;
-	}
-	ASSERT(licp != NULL);
-	/*
-	 * If we find a free descriptor, claim it,
-	 * initialize it, and return it.
-	 */
-	xfs_lic_claim(licp, i);
-	if (licp->lic_unused <= i) {
-		licp->lic_unused = i + 1;
-		xfs_lic_init_slot(licp, i);
-	}
-	lidp = xfs_lic_slot(licp, i);
-	tp->t_items_free--;
-	lidp->lid_item = lip;
-	lidp->lid_flags = 0;
-	lidp->lid_size = 0;
-	lip->li_desc = lidp;
-	lip->li_mountp = tp->t_mountp;
-	lip->li_ailp = tp->t_mountp->m_ail;
-	return lidp;
-}
-
-/*
- * Free the given descriptor.
- *
- * This requires setting the bit in the chunk's free mask corresponding
- * to the given slot.
- */
-void
-xfs_trans_free_item(xfs_trans_t	*tp, xfs_log_item_desc_t *lidp)
-{
-	uint			slot;
-	xfs_log_item_chunk_t	*licp;
-	xfs_log_item_chunk_t	**licpp;
-
-	slot = xfs_lic_desc_to_slot(lidp);
-	licp = xfs_lic_desc_to_chunk(lidp);
-	xfs_lic_relse(licp, slot);
-	lidp->lid_item->li_desc = NULL;
-	tp->t_items_free++;
-
-	/*
-	 * If there are no more used items in the chunk and this is not
-	 * the chunk embedded in the transaction structure, then free
-	 * the chunk. First pull it from the chunk list and then
-	 * free it back to the heap.  We didn't bother with a doubly
-	 * linked list here because the lists should be very short
-	 * and this is not a performance path.  It's better to save
-	 * the memory of the extra pointer.
-	 *
-	 * Also decrement the transaction structure's count of free items
-	 * by the number in a chunk since we are freeing an empty chunk.
-	 */
-	if (xfs_lic_are_all_free(licp) && (licp != &(tp->t_items))) {
-		licpp = &(tp->t_items.lic_next);
-		while (*licpp != licp) {
-			ASSERT(*licpp != NULL);
-			licpp = &((*licpp)->lic_next);
-		}
-		*licpp = licp->lic_next;
-		kmem_free(licp);
-		tp->t_items_free -= XFS_LIC_NUM_SLOTS;
-	}
-}
-
-/*
- * This is called to find the descriptor corresponding to the given
- * log item.  It returns a pointer to the descriptor.
- * The log item MUST have a corresponding descriptor in the given
- * transaction.  This routine does not return NULL, it panics.
- *
- * The descriptor pointer is kept in the log item's li_desc field.
- * Just return it.
- */
-/*ARGSUSED*/
-xfs_log_item_desc_t *
-xfs_trans_find_item(xfs_trans_t	*tp, xfs_log_item_t *lip)
-{
-	ASSERT(lip->li_desc != NULL);
-
-	return lip->li_desc;
-}
-
-
-/*
- * Return a pointer to the first descriptor in the chunk list.
- * This does not return NULL if there are none, it panics.
- *
- * The first descriptor must be in either the first or second chunk.
- * This is because the only chunk allowed to be empty is the first.
- * All others are freed when they become empty.
- *
- * At some point this and xfs_trans_next_item() should be optimized
- * to quickly look at the mask to determine if there is anything to
- * look at.
- */
-xfs_log_item_desc_t *
-xfs_trans_first_item(xfs_trans_t *tp)
-{
-	xfs_log_item_chunk_t	*licp;
-	int			i;
-
-	licp = &tp->t_items;
-	/*
-	 * If it's not in the first chunk, skip to the second.
-	 */
-	if (xfs_lic_are_all_free(licp)) {
-		licp = licp->lic_next;
-	}
-
-	/*
-	 * Return the first non-free descriptor in the chunk.
-	 */
-	ASSERT(!xfs_lic_are_all_free(licp));
-	for (i = 0; i < licp->lic_unused; i++) {
-		if (xfs_lic_isfree(licp, i)) {
-			continue;
-		}
-
-		return xfs_lic_slot(licp, i);
-	}
-	cmn_err(CE_WARN, "xfs_trans_first_item() -- no first item");
-	return NULL;
-}
-
-
-/*
- * Given a descriptor, return the next descriptor in the chunk list.
- * This returns NULL if there are no more used descriptors in the list.
- *
- * We do this by first locating the chunk in which the descriptor resides,
- * and then scanning forward in the chunk and the list for the next
- * used descriptor.
- */
-/*ARGSUSED*/
-xfs_log_item_desc_t *
-xfs_trans_next_item(xfs_trans_t *tp, xfs_log_item_desc_t *lidp)
-{
-	xfs_log_item_chunk_t	*licp;
-	int			i;
-
-	licp = xfs_lic_desc_to_chunk(lidp);
-
-	/*
-	 * First search the rest of the chunk. The for loop keeps us
-	 * from referencing things beyond the end of the chunk.
-	 */
-	for (i = (int)xfs_lic_desc_to_slot(lidp) + 1; i < licp->lic_unused; i++) {
-		if (xfs_lic_isfree(licp, i)) {
-			continue;
-		}
-
-		return xfs_lic_slot(licp, i);
-	}
-
-	/*
-	 * Now search the next chunk.  It must be there, because the
-	 * next chunk would have been freed if it were empty.
-	 * If there is no next chunk, return NULL.
-	 */
-	if (licp->lic_next == NULL) {
-		return NULL;
-	}
-
-	licp = licp->lic_next;
-	ASSERT(!xfs_lic_are_all_free(licp));
-	for (i = 0; i < licp->lic_unused; i++) {
-		if (xfs_lic_isfree(licp, i)) {
-			continue;
-		}
-
-		return xfs_lic_slot(licp, i);
-	}
-	ASSERT(0);
-	/* NOTREACHED */
-	return NULL; /* keep gcc quite */
-}
-
-/*
- * This is called to unlock all of the items of a transaction and to free
- * all the descriptors of that transaction.
- *
- * It walks the list of descriptors and unlocks each item.  It frees
- * each chunk except that embedded in the transaction as it goes along.
- */
-void
-xfs_trans_free_items(
-	xfs_trans_t	*tp,
-	xfs_lsn_t	commit_lsn,
-	int		flags)
-{
-	xfs_log_item_chunk_t	*licp;
-	xfs_log_item_chunk_t	*next_licp;
-	int			abort;
-
-	abort = flags & XFS_TRANS_ABORT;
-	licp = &tp->t_items;
-	/*
-	 * Special case the embedded chunk so we don't free it below.
-	 */
-	if (!xfs_lic_are_all_free(licp)) {
-		(void) xfs_trans_unlock_chunk(licp, 1, abort, commit_lsn);
-		xfs_lic_all_free(licp);
-		licp->lic_unused = 0;
-	}
-	licp = licp->lic_next;
-
-	/*
-	 * Unlock each item in each chunk and free the chunks.
-	 */
-	while (licp != NULL) {
-		ASSERT(!xfs_lic_are_all_free(licp));
-		(void) xfs_trans_unlock_chunk(licp, 1, abort, commit_lsn);
-		next_licp = licp->lic_next;
-		kmem_free(licp);
-		licp = next_licp;
-	}
-
-	/*
-	 * Reset the transaction structure's free item count.
-	 */
-	tp->t_items_free = XFS_LIC_NUM_SLOTS;
-	tp->t_items.lic_next = NULL;
-}
-
-
-
-/*
- * This is called to unlock the items associated with a transaction.
- * Items which were not logged should be freed.
- * Those which were logged must still be tracked so they can be unpinned
- * when the transaction commits.
- */
-void
-xfs_trans_unlock_items(xfs_trans_t *tp, xfs_lsn_t commit_lsn)
-{
-	xfs_log_item_chunk_t	*licp;
-	xfs_log_item_chunk_t	*next_licp;
-	xfs_log_item_chunk_t	**licpp;
-	int			freed;
-
-	freed = 0;
-	licp = &tp->t_items;
-
-	/*
-	 * Special case the embedded chunk so we don't free.
-	 */
-	if (!xfs_lic_are_all_free(licp)) {
-		freed = xfs_trans_unlock_chunk(licp, 0, 0, commit_lsn);
-	}
-	licpp = &(tp->t_items.lic_next);
-	licp = licp->lic_next;
-
-	/*
-	 * Unlock each item in each chunk, free non-dirty descriptors,
-	 * and free empty chunks.
-	 */
-	while (licp != NULL) {
-		ASSERT(!xfs_lic_are_all_free(licp));
-		freed += xfs_trans_unlock_chunk(licp, 0, 0, commit_lsn);
-		next_licp = licp->lic_next;
-		if (xfs_lic_are_all_free(licp)) {
-			*licpp = next_licp;
-			kmem_free(licp);
-			freed -= XFS_LIC_NUM_SLOTS;
-		} else {
-			licpp = &(licp->lic_next);
-		}
-		ASSERT(*licpp == next_licp);
-		licp = next_licp;
-	}
-
-	/*
-	 * Fix the free descriptor count in the transaction.
-	 */
-	tp->t_items_free += freed;
-}
-
-/*
- * Unlock each item pointed to by a descriptor in the given chunk.
- * Stamp the commit lsn into each item if necessary.
- * Free descriptors pointing to items which are not dirty if freeing_chunk
- * is zero. If freeing_chunk is non-zero, then we need to unlock all
- * items in the chunk.
- * 
- * Return the number of descriptors freed.
- */
-STATIC int
-xfs_trans_unlock_chunk(
-	xfs_log_item_chunk_t	*licp,
-	int			freeing_chunk,
-	int			abort,
-	xfs_lsn_t		commit_lsn)
-{
-	xfs_log_item_desc_t	*lidp;
-	xfs_log_item_t		*lip;
-	int			i;
-	int			freed;
-
-	freed = 0;
-	lidp = licp->lic_descs;
-	for (i = 0; i < licp->lic_unused; i++, lidp++) {
-		if (xfs_lic_isfree(licp, i)) {
-			continue;
-		}
-		lip = lidp->lid_item;
-		lip->li_desc = NULL;
-
-		if (commit_lsn != NULLCOMMITLSN)
-			IOP_COMMITTING(lip, commit_lsn);
-		if (abort)
-			lip->li_flags |= XFS_LI_ABORTED;
-		IOP_UNLOCK(lip);
-
-		/*
-		 * Free the descriptor if the item is not dirty
-		 * within this transaction and the caller is not
-		 * going to just free the entire thing regardless.
-		 */
-		if (!(freeing_chunk) &&
-		    (!(lidp->lid_flags & XFS_LID_DIRTY) || abort)) {
-			xfs_lic_relse(licp, i);
-			freed++;
-		}
-	}
-
-	return freed;
-}