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authorDave Chinner <dchinner@redhat.com>2010-12-03 17:00:52 +1100
committerDave Chinner <david@fromorbit.com>2010-12-03 17:00:52 +1100
commitc90821a26a8c90ad1e3116393b8a8260ab46bffb (patch)
tree1970fa2af39b277e375c059d0e5654e890c44511
parente677d0f9548e2245ee3c2977661ca8ca165af188 (diff)
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xfs: consume iodone callback items on buffers as they are processed
To allow buffer iodone callbacks to consume multiple items off the callback list, first we need to convert the xfs_buf_do_callbacks() to consume items and always pull the next item from the head of the list. The means the item list walk is never dependent on knowing the next item on the list and hence allows callbacks to remove items from the list as well. This allows callbacks to do bulk operations by scanning the list for identical callbacks, consuming them all and then processing them in bulk, negating the need for multiple callbacks of that type. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
-rw-r--r--fs/xfs/xfs_buf_item.c32
1 files changed, 21 insertions, 11 deletions
diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
index 2686d0d..ed2b65f 100644
--- a/fs/xfs/xfs_buf_item.c
+++ b/fs/xfs/xfs_buf_item.c
@@ -142,7 +142,7 @@ xfs_buf_item_log_check(
#endif
STATIC void xfs_buf_error_relse(xfs_buf_t *bp);
-STATIC void xfs_buf_do_callbacks(xfs_buf_t *bp, xfs_log_item_t *lip);
+STATIC void xfs_buf_do_callbacks(struct xfs_buf *bp);
/*
* This returns the number of log iovecs needed to log the
@@ -450,7 +450,7 @@ xfs_buf_item_unpin(
* xfs_trans_ail_delete() drops the AIL lock.
*/
if (bip->bli_flags & XFS_BLI_STALE_INODE) {
- xfs_buf_do_callbacks(bp, (xfs_log_item_t *)bip);
+ xfs_buf_do_callbacks(bp);
XFS_BUF_SET_FSPRIVATE(bp, NULL);
XFS_BUF_CLR_IODONE_FUNC(bp);
} else {
@@ -918,15 +918,26 @@ xfs_buf_attach_iodone(
XFS_BUF_SET_IODONE_FUNC(bp, xfs_buf_iodone_callbacks);
}
+/*
+ * We can have many callbacks on a buffer. Running the callbacks individually
+ * can cause a lot of contention on the AIL lock, so we allow for a single
+ * callback to be able to scan the remaining lip->li_bio_list for other items
+ * of the same type and callback to be processed in the first call.
+ *
+ * As a result, the loop walking the callback list below will also modify the
+ * list. it removes the first item from the list and then runs the callback.
+ * The loop then restarts from the new head of the list. This allows the
+ * callback to scan and modify the list attached to the buffer and we don't
+ * have to care about maintaining a next item pointer.
+ */
STATIC void
xfs_buf_do_callbacks(
- xfs_buf_t *bp,
- xfs_log_item_t *lip)
+ struct xfs_buf *bp)
{
- xfs_log_item_t *nlip;
+ struct xfs_log_item *lip;
- while (lip != NULL) {
- nlip = lip->li_bio_list;
+ while ((lip = XFS_BUF_FSPRIVATE(bp, xfs_log_item_t *)) != NULL) {
+ XFS_BUF_SET_FSPRIVATE(bp, lip->li_bio_list);
ASSERT(lip->li_cb != NULL);
/*
* Clear the next pointer so we don't have any
@@ -936,7 +947,6 @@ xfs_buf_do_callbacks(
*/
lip->li_bio_list = NULL;
lip->li_cb(bp, lip);
- lip = nlip;
}
}
@@ -970,7 +980,7 @@ xfs_buf_iodone_callbacks(
ASSERT(XFS_BUF_TARGET(bp) == mp->m_ddev_targp);
XFS_BUF_SUPER_STALE(bp);
trace_xfs_buf_item_iodone(bp, _RET_IP_);
- xfs_buf_do_callbacks(bp, lip);
+ xfs_buf_do_callbacks(bp);
XFS_BUF_SET_FSPRIVATE(bp, NULL);
XFS_BUF_CLR_IODONE_FUNC(bp);
xfs_buf_ioend(bp, 0);
@@ -1029,7 +1039,7 @@ xfs_buf_iodone_callbacks(
return;
}
- xfs_buf_do_callbacks(bp, lip);
+ xfs_buf_do_callbacks(bp);
XFS_BUF_SET_FSPRIVATE(bp, NULL);
XFS_BUF_CLR_IODONE_FUNC(bp);
xfs_buf_ioend(bp, 0);
@@ -1063,7 +1073,7 @@ xfs_buf_error_relse(
* We have to unpin the pinned buffers so do the
* callbacks.
*/
- xfs_buf_do_callbacks(bp, lip);
+ xfs_buf_do_callbacks(bp);
XFS_BUF_SET_FSPRIVATE(bp, NULL);
XFS_BUF_CLR_IODONE_FUNC(bp);
XFS_BUF_SET_BRELSE_FUNC(bp,NULL);