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>
diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
index e639e8e..0c903eb 100644
--- a/fs/xfs/xfs_trans.h
+++ b/fs/xfs/xfs_trans.h
@@ -161,105 +161,14 @@
* the amount of space needed to log the item it describes
* once we get to commit processing (see xfs_trans_commit()).
*/
-typedef struct xfs_log_item_desc {
+struct xfs_log_item_desc {
struct xfs_log_item *lid_item;
- ushort lid_size;
- unsigned char lid_flags;
- unsigned char lid_index;
-} xfs_log_item_desc_t;
+ ushort lid_size;
+ unsigned char lid_flags;
+ struct list_head lid_trans;
+};
#define XFS_LID_DIRTY 0x1
-#define XFS_LID_PINNED 0x2
-
-/*
- * This structure is used to maintain a chunk list of log_item_desc
- * structures. The free field is a bitmask indicating which descriptors
- * in this chunk's array are free. The unused field is the first value
- * not used since this chunk was allocated.
- */
-#define XFS_LIC_NUM_SLOTS 15
-typedef struct xfs_log_item_chunk {
- struct xfs_log_item_chunk *lic_next;
- ushort lic_free;
- ushort lic_unused;
- xfs_log_item_desc_t lic_descs[XFS_LIC_NUM_SLOTS];
-} xfs_log_item_chunk_t;
-
-#define XFS_LIC_MAX_SLOT (XFS_LIC_NUM_SLOTS - 1)
-#define XFS_LIC_FREEMASK ((1 << XFS_LIC_NUM_SLOTS) - 1)
-
-
-/*
- * Initialize the given chunk. Set the chunk's free descriptor mask
- * to indicate that all descriptors are free. The caller gets to set
- * lic_unused to the right value (0 matches all free). The
- * lic_descs.lid_index values are set up as each desc is allocated.
- */
-static inline void xfs_lic_init(xfs_log_item_chunk_t *cp)
-{
- cp->lic_free = XFS_LIC_FREEMASK;
-}
-
-static inline void xfs_lic_init_slot(xfs_log_item_chunk_t *cp, int slot)
-{
- cp->lic_descs[slot].lid_index = (unsigned char)(slot);
-}
-
-static inline int xfs_lic_vacancy(xfs_log_item_chunk_t *cp)
-{
- return cp->lic_free & XFS_LIC_FREEMASK;
-}
-
-static inline void xfs_lic_all_free(xfs_log_item_chunk_t *cp)
-{
- cp->lic_free = XFS_LIC_FREEMASK;
-}
-
-static inline int xfs_lic_are_all_free(xfs_log_item_chunk_t *cp)
-{
- return ((cp->lic_free & XFS_LIC_FREEMASK) == XFS_LIC_FREEMASK);
-}
-
-static inline int xfs_lic_isfree(xfs_log_item_chunk_t *cp, int slot)
-{
- return (cp->lic_free & (1 << slot));
-}
-
-static inline void xfs_lic_claim(xfs_log_item_chunk_t *cp, int slot)
-{
- cp->lic_free &= ~(1 << slot);
-}
-
-static inline void xfs_lic_relse(xfs_log_item_chunk_t *cp, int slot)
-{
- cp->lic_free |= 1 << slot;
-}
-
-static inline xfs_log_item_desc_t *
-xfs_lic_slot(xfs_log_item_chunk_t *cp, int slot)
-{
- return &(cp->lic_descs[slot]);
-}
-
-static inline int xfs_lic_desc_to_slot(xfs_log_item_desc_t *dp)
-{
- return (uint)dp->lid_index;
-}
-
-/*
- * Calculate the address of a chunk given a descriptor pointer:
- * dp - dp->lid_index give the address of the start of the lic_descs array.
- * From this we subtract the offset of the lic_descs field in a chunk.
- * All of this yields the address of the chunk, which is
- * cast to a chunk pointer.
- */
-static inline xfs_log_item_chunk_t *
-xfs_lic_desc_to_chunk(xfs_log_item_desc_t *dp)
-{
- return (xfs_log_item_chunk_t*) \
- (((xfs_caddr_t)((dp) - (dp)->lid_index)) - \
- (xfs_caddr_t)(((xfs_log_item_chunk_t*)0)->lic_descs));
-}
#define XFS_TRANS_MAGIC 0x5452414E /* 'TRAN' */
/*
@@ -516,8 +425,7 @@
int64_t t_rblocks_delta;/* superblock rblocks change */
int64_t t_rextents_delta;/* superblocks rextents chg */
int64_t t_rextslog_delta;/* superblocks rextslog chg */
- unsigned int t_items_free; /* log item descs free */
- xfs_log_item_chunk_t t_items; /* first log item desc chunk */
+ struct list_head t_items; /* log item descriptors */
xfs_trans_header_t t_header; /* header for in-log trans */
struct list_head t_busy; /* list of busy extents */
unsigned long t_pflags; /* saved process flags state */
@@ -595,6 +503,7 @@
void xfs_trans_ail_destroy(struct xfs_mount *);
extern kmem_zone_t *xfs_trans_zone;
+extern kmem_zone_t *xfs_log_item_desc_zone;
#endif /* __KERNEL__ */