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-rw-r--r--fs/xfs/xfs_buf_item.c110
1 files changed, 50 insertions, 60 deletions
diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
index 240340a..4cd5f61 100644
--- a/fs/xfs/xfs_buf_item.c
+++ b/fs/xfs/xfs_buf_item.c
@@ -341,10 +341,15 @@ xfs_buf_item_format(
}
/*
- * This is called to pin the buffer associated with the buf log
- * item in memory so it cannot be written out. Simply call bpin()
- * on the buffer to do this.
+ * This is called to pin the buffer associated with the buf log item in memory
+ * so it cannot be written out. Simply call bpin() on the buffer to do this.
+ *
+ * We also always take a reference to the buffer log item here so that the bli
+ * is held while the item is pinned in memory. This means that we can
+ * unconditionally drop the reference count a transaction holds when the
+ * transaction is completed.
*/
+
STATIC void
xfs_buf_item_pin(
xfs_buf_log_item_t *bip)
@@ -356,6 +361,7 @@ xfs_buf_item_pin(
ASSERT(atomic_read(&bip->bli_refcount) > 0);
ASSERT((bip->bli_flags & XFS_BLI_LOGGED) ||
(bip->bli_flags & XFS_BLI_STALE));
+ atomic_inc(&bip->bli_refcount);
trace_xfs_buf_item_pin(bip);
xfs_bpin(bp);
}
@@ -489,20 +495,23 @@ xfs_buf_item_trylock(
}
/*
- * Release the buffer associated with the buf log item.
- * If there is no dirty logged data associated with the
- * buffer recorded in the buf log item, then free the
- * buf log item and remove the reference to it in the
- * buffer.
+ * Release the buffer associated with the buf log item. If there is no dirty
+ * logged data associated with the buffer recorded in the buf log item, then
+ * free the buf log item and remove the reference to it in the buffer.
*
- * This call ignores the recursion count. It is only called
- * when the buffer should REALLY be unlocked, regardless
- * of the recursion count.
+ * This call ignores the recursion count. It is only called when the buffer
+ * should REALLY be unlocked, regardless of the recursion count.
*
- * If the XFS_BLI_HOLD flag is set in the buf log item, then
- * free the log item 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.
+ * We unconditionally drop the transaction's reference to the log item. If the
+ * item was logged, then another reference was taken when it was pinned, so we
+ * can safely drop the transaction reference now. This also allows us to avoid
+ * potential races with the unpin code freeing the bli by not referencing the
+ * bli after we've dropped the reference count.
+ *
+ * If the XFS_BLI_HOLD flag is set in the buf log item, then free the log item
+ * 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.
*/
STATIC void
xfs_buf_item_unlock(
@@ -514,73 +523,54 @@ xfs_buf_item_unlock(
bp = bip->bli_buf;
- /*
- * Clear the buffer's association with this transaction.
- */
+ /* Clear the buffer's association with this transaction. */
XFS_BUF_SET_FSPRIVATE2(bp, NULL);
/*
- * If this is a transaction abort, don't return early.
- * Instead, allow the brelse to happen.
- * Normally it would be done for stale (cancelled) buffers
- * at unpin time, but we'll never go through the pin/unpin
- * cycle if we abort inside commit.
+ * If this is a transaction abort, don't return early. Instead, allow
+ * the brelse to happen. Normally it would be done for stale
+ * (cancelled) buffers at unpin time, but we'll never go through the
+ * pin/unpin cycle if we abort inside commit.
*/
aborted = (bip->bli_item.li_flags & XFS_LI_ABORTED) != 0;
/*
- * If the buf item is marked stale, then don't do anything.
- * We'll unlock the buffer and free the buf item when the
- * buffer is unpinned for the last time.
+ * Before possibly freeing the buf item, determine if we should
+ * release the buffer at the end of this routine.
+ */
+ hold = bip->bli_flags & XFS_BLI_HOLD;
+
+ /* Clear the per transaction state. */
+ bip->bli_flags &= ~(XFS_BLI_LOGGED | XFS_BLI_HOLD);
+
+ /*
+ * If the buf item is marked stale, then don't do anything. We'll
+ * unlock the buffer and free the buf item when the buffer is unpinned
+ * for the last time.
*/
if (bip->bli_flags & XFS_BLI_STALE) {
- bip->bli_flags &= ~XFS_BLI_LOGGED;
trace_xfs_buf_item_unlock_stale(bip);
ASSERT(bip->bli_format.blf_flags & XFS_BLI_CANCEL);
- if (!aborted)
+ if (!aborted) {
+ atomic_dec(&bip->bli_refcount);
return;
+ }
}
- /*
- * Drop the transaction's reference to the log item if
- * it was not logged as part of the transaction. Otherwise
- * we'll drop the reference in xfs_buf_item_unpin() when
- * the transaction is really through with the buffer.
- */
- if (!(bip->bli_flags & XFS_BLI_LOGGED)) {
- atomic_dec(&bip->bli_refcount);
- } else {
- /*
- * Clear the logged flag since this is per
- * transaction state.
- */
- bip->bli_flags &= ~XFS_BLI_LOGGED;
- }
-
- /*
- * Before possibly freeing the buf item, determine if we should
- * release the buffer at the end of this routine.
- */
- hold = bip->bli_flags & XFS_BLI_HOLD;
trace_xfs_buf_item_unlock(bip);
/*
- * If the buf item isn't tracking any data, free it.
- * Otherwise, if XFS_BLI_HOLD is set clear it.
+ * If the buf item isn't tracking any data, free it, otherwise drop the
+ * reference we hold to it.
*/
if (xfs_bitmap_empty(bip->bli_format.blf_data_map,
- bip->bli_format.blf_map_size)) {
+ bip->bli_format.blf_map_size))
xfs_buf_item_relse(bp);
- } else if (hold) {
- bip->bli_flags &= ~XFS_BLI_HOLD;
- }
+ else
+ atomic_dec(&bip->bli_refcount);
- /*
- * Release the buffer if XFS_BLI_HOLD was not set.
- */
- if (!hold) {
+ if (!hold)
xfs_buf_relse(bp);
- }
}
/*
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