* Drop the buffer log item refcount and take appropriate action. This helper
* determines whether the bli must be freed or not, since a decrement to zero
* does not necessarily mean the bli is unused.
- *
- * Return true if the bli is freed, false otherwise.
*/
-bool
+void
xfs_buf_item_put(
struct xfs_buf_log_item *bip)
{
- struct xfs_log_item *lip = &bip->bli_item;
- bool aborted;
- bool dirty;
+
+ ASSERT(xfs_buf_islocked(bip->bli_buf));
/* drop the bli ref and return if it wasn't the last one */
if (!atomic_dec_and_test(&bip->bli_refcount))
- return false;
+ return;
- /*
- * We dropped the last ref and must free the item if clean or aborted.
- * If the bli is dirty and non-aborted, the buffer was clean in the
- * transaction but still awaiting writeback from previous changes. In
- * that case, the bli is freed on buffer writeback completion.
- */
- aborted = test_bit(XFS_LI_ABORTED, &lip->li_flags) ||
- xlog_is_shutdown(lip->li_log);
- dirty = bip->bli_flags & XFS_BLI_DIRTY;
- if (dirty && !aborted)
- return false;
+ /* If the BLI is in the AIL, then it is still dirty and in use */
+ if (test_bit(XFS_LI_IN_AIL, &bip->bli_item.li_flags)) {
+ ASSERT(bip->bli_flags & XFS_BLI_DIRTY);
+ return;
+ }
/*
- * The bli is aborted or clean. An aborted item may be in the AIL
- * regardless of dirty state. For example, consider an aborted
- * transaction that invalidated a dirty bli and cleared the dirty
- * state.
+ * In shutdown conditions, we can be asked to free a dirty BLI that
+ * isn't in the AIL. This can occur due to a checkpoint aborting a BLI
+ * instead of inserting it into the AIL at checkpoint IO completion. If
+ * there's another bli reference (e.g. a btree cursor holds a clean
+ * reference) and it is released via xfs_trans_brelse(), we can get here
+ * with that aborted, dirty BLI. In this case, it is safe to free the
+ * dirty BLI immediately, as it is not in the AIL and there are no
+ * other references to it.
+ *
+ * We should never get here with a stale BLI via that path as
+ * xfs_trans_brelse() specifically holds onto stale buffers rather than
+ * releasing them.
*/
- if (aborted)
- xfs_trans_ail_delete(lip, 0);
+ ASSERT(!(bip->bli_flags & XFS_BLI_DIRTY) ||
+ test_bit(XFS_LI_ABORTED, &bip->bli_item.li_flags));
+ ASSERT(!(bip->bli_flags & XFS_BLI_STALE));
xfs_buf_item_relse(bip);
- return true;
}
/*
* if necessary but do not unlock the buffer. This is for support of
* xfs_trans_bhold(). Make sure the XFS_BLI_HOLD field is cleared if we don't
* free the item.
+ *
+ * If the XFS_BLI_STALE flag is set, the last reference to the BLI *must*
+ * perform a completion abort of any objects attached to the buffer for IO
+ * tracking purposes. This generally only happens in shutdown situations,
+ * normally xfs_buf_item_unpin() will drop the last BLI reference and perform
+ * completion processing. However, because transaction completion can race with
+ * checkpoint completion during a shutdown, this release context may end up
+ * being the last active reference to the BLI and so needs to perform this
+ * cleanup.
*/
STATIC void
xfs_buf_item_release(
{
struct xfs_buf_log_item *bip = BUF_ITEM(lip);
struct xfs_buf *bp = bip->bli_buf;
- bool released;
bool hold = bip->bli_flags & XFS_BLI_HOLD;
bool stale = bip->bli_flags & XFS_BLI_STALE;
-#if defined(DEBUG) || defined(XFS_WARN)
- bool ordered = bip->bli_flags & XFS_BLI_ORDERED;
- bool dirty = bip->bli_flags & XFS_BLI_DIRTY;
bool aborted = test_bit(XFS_LI_ABORTED,
&lip->li_flags);
+ bool dirty = bip->bli_flags & XFS_BLI_DIRTY;
+#if defined(DEBUG) || defined(XFS_WARN)
+ bool ordered = bip->bli_flags & XFS_BLI_ORDERED;
#endif
trace_xfs_buf_item_release(bip);
+ ASSERT(xfs_buf_islocked(bp));
+
/*
* The bli dirty state should match whether the blf has logged segments
* except for ordered buffers, where only the bli should be dirty.
bp->b_transp = NULL;
bip->bli_flags &= ~(XFS_BLI_LOGGED | XFS_BLI_HOLD | XFS_BLI_ORDERED);
+ /* If there are other references, then we have nothing to do. */
+ if (!atomic_dec_and_test(&bip->bli_refcount))
+ goto out_release;
+
+ /*
+ * Stale buffer completion frees the BLI, unlocks and releases the
+ * buffer. Neither the BLI or buffer are safe to reference after this
+ * call, so there's nothing more we need to do here.
+ *
+ * If we get here with a stale buffer and references to the BLI remain,
+ * we must not unlock the buffer as the last BLI reference owns lock
+ * context, not us.
+ */
+ if (stale) {
+ xfs_buf_item_finish_stale(bip);
+ xfs_buf_relse(bp);
+ ASSERT(!hold);
+ return;
+ }
+
+ /*
+ * Dirty or clean, aborted items are done and need to be removed from
+ * the AIL and released. This frees the BLI, but leaves the buffer
+ * locked and referenced.
+ */
+ if (aborted || xlog_is_shutdown(lip->li_log)) {
+ ASSERT(list_empty(&bip->bli_buf->b_li_list));
+ xfs_buf_item_done(bp);
+ goto out_release;
+ }
+
+ /*
+ * Clean, unreferenced BLIs can be immediately freed, leaving the buffer
+ * locked and referenced.
+ *
+ * Dirty, unreferenced BLIs *must* be in the AIL awaiting writeback.
+ */
+ if (!dirty)
+ xfs_buf_item_relse(bip);
+ else
+ ASSERT(test_bit(XFS_LI_IN_AIL, &lip->li_flags));
+
+ /* Not safe to reference the BLI from here */
+out_release:
/*
- * Unref the item and unlock the buffer unless held or stale. Stale
- * buffers remain locked until final unpin unless the bli is freed by
- * the unref call. The latter implies shutdown because buffer
- * invalidation dirties the bli and transaction.
+ * If we get here with a stale buffer, we must not unlock the
+ * buffer as the last BLI reference owns lock context, not us.
*/
- released = xfs_buf_item_put(bip);
- if (hold || (stale && !released))
+ if (stale || hold)
return;
- ASSERT(!stale || aborted);
xfs_buf_relse(bp);
}
projects / users / hch / xfs.git / commitdiff