[v8,37/39] xfsprogs: Add delay ready attr remove routines
diff mbox series

Message ID 20200403220958.4944-38-allison.henderson@oracle.com
State Superseded
Headers show
Series
  • xfsprogs: Delay Ready Attributes
Related show

Commit Message

Allison Collins April 3, 2020, 10:09 p.m. UTC
This patch modifies the attr remove routines to be delay ready. This
means they no longer roll or commit transactions, but instead return
-EAGAIN to have the calling routine roll and refresh the transaction. In
this series, xfs_attr_remove_args has become xfs_attr_remove_iter, which
uses a sort of state machine like switch to keep track of where it was
when EAGAIN was returned. xfs_attr_node_removename has also been
modified to use the switch, and a new version of xfs_attr_remove_args
consists of a simple loop to refresh the transaction until the operation
is completed.

Calls to xfs_attr_rmtval_remove are replaced with the delay ready
counter parts: xfs_attr_rmtval_invalidate (appearing in the setup
helper) and then __xfs_attr_rmtval_remove. We will rename
__xfs_attr_rmtval_remove back to xfs_attr_rmtval_remove when we are
done.

This patch also adds a new struct xfs_delattr_context, which we will use
to keep track of the current state of an attribute operation. The new
xfs_delattr_state enum is used to track various operations that are in
progress so that we know not to repeat them, and resume where we left
off before EAGAIN was returned to cycle out the transaction. Other
members take the place of local variables that need to retain their
values across multiple function recalls.

Below is a state machine diagram for attr remove operations. The
XFS_DAS_* states indicate places where the function would return
-EAGAIN, and then immediately resume from after being recalled by the
calling function.  States marked as a "subroutine state" indicate that
they belong to a subroutine, and so the calling function needs to pass
them back to that subroutine to allow it to finish where it left off.
But they otherwise do not have a role in the calling function other than
just passing through.

 xfs_attr_remove_iter()
         XFS_DAS_RM_SHRINK     ─┐
         (subroutine state)     │
                                │
         XFS_DAS_RMTVAL_REMOVE ─┤
         (subroutine state)     │
                                └─>xfs_attr_node_removename()
                                                 │
                                                 v
                                         need to remove
                                   ┌─n──  rmt blocks?
                                   │             │
                                   │             y
                                   │             │
                                   │             v
                                   │  ┌─>XFS_DAS_RMTVAL_REMOVE
                                   │  │          │
                                   │  │          v
                                   │  └──y── more blks
                                   │         to remove?
                                   │             │
                                   │             n
                                   │             │
                                   │             v
                                   │         need to
                                   └─────> shrink tree? ─n─┐
                                                 │         │
                                                 y         │
                                                 │         │
                                                 v         │
                                         XFS_DAS_RM_SHRINK │
                                                 │         │
                                                 v         │
                                                done <─────┘

Signed-off-by: Allison Collins <allison.henderson@oracle.com>
---
 libxfs/xfs_attr.c | 168 ++++++++++++++++++++++++++++++++++++++++++------------
 libxfs/xfs_attr.h |  38 ++++++++++++
 2 files changed, 168 insertions(+), 38 deletions(-)

Patch
diff mbox series

diff --git a/libxfs/xfs_attr.c b/libxfs/xfs_attr.c
index fa706f5..59d46a4 100644
--- a/libxfs/xfs_attr.c
+++ b/libxfs/xfs_attr.c
@@ -46,7 +46,7 @@  STATIC int xfs_attr_shortform_addname(xfs_da_args_t *args);
  */
 STATIC int xfs_attr_leaf_get(xfs_da_args_t *args);
 STATIC int xfs_attr_leaf_addname(xfs_da_args_t *args);
-STATIC int xfs_attr_leaf_removename(xfs_da_args_t *args);
+STATIC int xfs_attr_leaf_removename(struct xfs_delattr_context *dac);
 STATIC int xfs_attr_leaf_hasname(struct xfs_da_args *args, struct xfs_buf **bp);
 
 /*
@@ -54,12 +54,21 @@  STATIC int xfs_attr_leaf_hasname(struct xfs_da_args *args, struct xfs_buf **bp);
  */
 STATIC int xfs_attr_node_get(xfs_da_args_t *args);
 STATIC int xfs_attr_node_addname(xfs_da_args_t *args);
-STATIC int xfs_attr_node_removename(xfs_da_args_t *args);
+STATIC int xfs_attr_node_removename(struct xfs_delattr_context *dac);
 STATIC int xfs_attr_node_hasname(xfs_da_args_t *args,
 				 struct xfs_da_state **state);
 STATIC int xfs_attr_fillstate(xfs_da_state_t *state);
 STATIC int xfs_attr_refillstate(xfs_da_state_t *state);
 
+STATIC void
+xfs_delattr_context_init(
+	struct xfs_delattr_context	*dac,
+	struct xfs_da_args		*args)
+{
+	memset(dac, 0, sizeof(struct xfs_delattr_context));
+	dac->da_args = args;
+}
+
 int
 xfs_inode_hasattr(
 	struct xfs_inode	*ip)
@@ -357,20 +366,66 @@  xfs_has_attr(
  */
 int
 xfs_attr_remove_args(
-	struct xfs_da_args      *args)
+	struct xfs_da_args	*args)
 {
+	int			error = 0;
+	struct			xfs_delattr_context dac;
+
+	xfs_delattr_context_init(&dac, args);
+
+	do {
+		error = xfs_attr_remove_iter(&dac);
+		if (error != -EAGAIN)
+			break;
+
+		if (dac.flags & XFS_DAC_DEFER_FINISH) {
+			dac.flags &= ~XFS_DAC_DEFER_FINISH;
+			error = xfs_defer_finish(&args->trans);
+			if (error)
+				break;
+		}
+
+		error = xfs_trans_roll_inode(&args->trans, args->dp);
+		if (error)
+			break;
+	} while (true);
+
+	return error;
+}
+
+/*
+ * Remove the attribute specified in @args.
+ *
+ * This function may return -EAGAIN to signal that the transaction needs to be
+ * rolled.  Callers should continue calling this function until they receive a
+ * return value other than -EAGAIN.
+ */
+int
+xfs_attr_remove_iter(
+	struct xfs_delattr_context *dac)
+{
+	struct xfs_da_args	*args = dac->da_args;
 	struct xfs_inode	*dp = args->dp;
 	int			error;
 
+	/* State machine switch */
+	switch (dac->dela_state) {
+	case XFS_DAS_RM_SHRINK:
+	case XFS_DAS_RMTVAL_REMOVE:
+		return xfs_attr_node_removename(dac);
+	default:
+		break;
+	}
+
 	if (!xfs_inode_hasattr(dp)) {
 		error = -ENOATTR;
 	} else if (dp->i_d.di_aformat == XFS_DINODE_FMT_LOCAL) {
 		ASSERT(dp->i_afp->if_flags & XFS_IFINLINE);
 		error = xfs_attr_shortform_remove(args);
 	} else if (xfs_bmap_one_block(dp, XFS_ATTR_FORK)) {
-		error = xfs_attr_leaf_removename(args);
+		error = xfs_attr_leaf_removename(dac);
 	} else {
-		error = xfs_attr_node_removename(args);
+		error = xfs_attr_node_removename(dac);
 	}
 
 	return error;
@@ -795,11 +850,12 @@  xfs_attr_leaf_hasname(
  */
 STATIC int
 xfs_attr_leaf_removename(
-	struct xfs_da_args	*args)
+	struct xfs_delattr_context	*dac)
 {
-	struct xfs_inode	*dp;
-	struct xfs_buf		*bp;
-	int			error, forkoff;
+	struct xfs_da_args		*args = dac->da_args;
+	struct xfs_inode		*dp;
+	struct xfs_buf			*bp;
+	int				error, forkoff;
 
 	trace_xfs_attr_leaf_removename(args);
 
@@ -826,9 +882,8 @@  xfs_attr_leaf_removename(
 		/* bp is gone due to xfs_da_shrink_inode */
 		if (error)
 			return error;
-		error = xfs_defer_finish(&args->trans);
-		if (error)
-			return error;
+
+		dac->flags |= XFS_DAC_DEFER_FINISH;
 	}
 	return 0;
 }
@@ -1129,12 +1184,13 @@  out:
  */
 STATIC int
 xfs_attr_node_shrink(
-	struct xfs_da_args	*args,
-	struct xfs_da_state     *state)
+	struct xfs_delattr_context	*dac,
+	struct xfs_da_state		*state)
 {
-	struct xfs_inode	*dp = args->dp;
-	int			error, forkoff;
-	struct xfs_buf		*bp;
+	struct xfs_da_args		*args = dac->da_args;
+	struct xfs_inode		*dp = args->dp;
+	int				error, forkoff;
+	struct xfs_buf			*bp;
 
 	/*
 	 * Have to get rid of the copy of this dabuf in the state.
@@ -1154,9 +1210,7 @@  xfs_attr_node_shrink(
 		if (error)
 			return error;
 
-		error = xfs_defer_finish(&args->trans);
-		if (error)
-			return error;
+		dac->flags |= XFS_DAC_DEFER_FINISH;
 	} else
 		xfs_trans_brelse(args->trans, bp);
 
@@ -1195,13 +1249,15 @@  xfs_attr_leaf_mark_incomplete(
 
 /*
  * Initial setup for xfs_attr_node_removename.  Make sure the attr is there and
- * the blocks are valid.  Any remote blocks will be marked incomplete.
+ * the blocks are valid.  Any remote blocks will be marked incomplete and
+ * invalidated.
  */
 STATIC
 int xfs_attr_node_removename_setup(
-	struct xfs_da_args	*args,
-	struct xfs_da_state	**state)
+	struct xfs_delattr_context	*dac,
+	struct xfs_da_state		**state)
 {
+	struct xfs_da_args	*args = dac->da_args;
 	int			error;
 	struct xfs_da_state_blk	*blk;
 
@@ -1213,10 +1269,21 @@  int xfs_attr_node_removename_setup(
 	ASSERT(blk->bp != NULL);
 	ASSERT(blk->magic == XFS_ATTR_LEAF_MAGIC);
 
+	/*
+	 * Store blk and state in the context incase we need to cycle out the
+	 * transaction
+	 */
+	dac->blk = blk;
+	dac->da_state = *state;
+
 	if (args->rmtblkno > 0) {
 		error = xfs_attr_leaf_mark_incomplete(args, *state);
 		if (error)
 			return error;
+
+		error = xfs_attr_rmtval_invalidate(args);
+		if (error)
+			return error;
 	}
 
 	return 0;
@@ -1229,7 +1296,10 @@  xfs_attr_node_removename_rmt (
 {
 	int			error = 0;
 
-	error = xfs_attr_rmtval_remove(args);
+	/*
+	 * May return -EAGAIN to request that the caller recall this function
+	 */
+	error = __xfs_attr_rmtval_remove(args);
 	if (error)
 		return error;
 
@@ -1250,19 +1320,37 @@  xfs_attr_node_removename_rmt (
  * This will involve walking down the Btree, and may involve joining
  * leaf nodes and even joining intermediate nodes up to and including
  * the root node (a special case of an intermediate node).
+ *
+ * This routine is meant to function as either an inline or delayed operation,
+ * and may return -EAGAIN when the transaction needs to be rolled.  Calling
+ * functions will need to handle this, and recall the function until a
+ * successful error code is returned.
  */
 STATIC int
 xfs_attr_node_removename(
-	struct xfs_da_args	*args)
+	struct xfs_delattr_context	*dac)
 {
+	struct xfs_da_args	*args = dac->da_args;
 	struct xfs_da_state	*state;
 	struct xfs_da_state_blk	*blk;
 	int			retval, error;
 	struct xfs_inode	*dp = args->dp;
 
 	trace_xfs_attr_node_removename(args);
+	state = dac->da_state;
+	blk = dac->blk;
+
+	/* State machine switch */
+	switch (dac->dela_state) {
+	case XFS_DAS_RMTVAL_REMOVE:
+		goto das_rmtval_remove;
+	case XFS_DAS_RM_SHRINK:
+		goto das_rm_shrink;
+	default:
+		break;
+	}
 
-	error = xfs_attr_node_removename_setup(args, &state);
+	error = xfs_attr_node_removename_setup(dac, &state);
 	if (error)
 		goto out;
 
@@ -1271,10 +1359,16 @@  xfs_attr_node_removename(
 	 * This is done before we remove the attribute so that we don't
 	 * overflow the maximum size of a transaction and/or hit a deadlock.
 	 */
+
+das_rmtval_remove:
+
 	if (args->rmtblkno > 0) {
 		error = xfs_attr_node_removename_rmt(args, state);
-		if (error)
-			goto out;
+		if (error) {
+			if (error == -EAGAIN)
+				dac->dela_state = XFS_DAS_RMTVAL_REMOVE;
+			return error;
+		}
 	}
 
 	/*
@@ -1292,22 +1386,20 @@  xfs_attr_node_removename(
 		error = xfs_da3_join(state);
 		if (error)
 			goto out;
-		error = xfs_defer_finish(&args->trans);
-		if (error)
-			goto out;
-		/*
-		 * Commit the Btree join operation and start a new trans.
-		 */
-		error = xfs_trans_roll_inode(&args->trans, dp);
-		if (error)
-			goto out;
+
+		dac->flags |= XFS_DAC_DEFER_FINISH;
+		dac->dela_state = XFS_DAS_RM_SHRINK;
+		return -EAGAIN;
 	}
 
+das_rm_shrink:
+	dac->dela_state = XFS_DAS_RM_SHRINK;
+
 	/*
 	 * If the result is small enough, push it all into the inode.
 	 */
 	if (xfs_bmap_one_block(dp, XFS_ATTR_FORK))
-		error = xfs_attr_node_shrink(args, state);
+		error = xfs_attr_node_shrink(dac, state);
 
 	error = 0;
 out:
diff --git a/libxfs/xfs_attr.h b/libxfs/xfs_attr.h
index 66575b8..0e8ae1a 100644
--- a/libxfs/xfs_attr.h
+++ b/libxfs/xfs_attr.h
@@ -74,6 +74,43 @@  struct xfs_attr_list_context {
 };
 
 
+/*
+ * ========================================================================
+ * Structure used to pass context around among the delayed routines.
+ * ========================================================================
+ */
+
+/*
+ * Enum values for xfs_delattr_context.da_state
+ *
+ * These values are used by delayed attribute operations to keep track  of where
+ * they were before they returned -EAGAIN.  A return code of -EAGAIN signals the
+ * calling function to roll the transaction, and then recall the subroutine to
+ * finish the operation.  The enum is then used by the subroutine to jump back
+ * to where it was and resume executing where it left off.
+ */
+enum xfs_delattr_state {
+				      /* Zero is uninitalized */
+	XFS_DAS_RM_SHRINK	= 1,  /* We are shrinking the tree */
+	XFS_DAS_RMTVAL_REMOVE,	      /* We are removing remote value blocks */
+};
+
+/*
+ * Defines for xfs_delattr_context.flags
+ */
+#define XFS_DAC_DEFER_FINISH    0x1 /* indicates to finish the transaction */
+
+/*
+ * Context used for keeping track of delayed attribute operations
+ */
+struct xfs_delattr_context {
+	struct xfs_da_args      *da_args;
+	struct xfs_da_state     *da_state;
+	struct xfs_da_state_blk *blk;
+	unsigned int            flags;
+	enum xfs_delattr_state  dela_state;
+};
+
 /*========================================================================
  * Function prototypes for the kernel.
  *========================================================================*/
@@ -91,6 +128,7 @@  int xfs_attr_set(struct xfs_da_args *args);
 int xfs_attr_set_args(struct xfs_da_args *args);
 int xfs_has_attr(struct xfs_da_args *args);
 int xfs_attr_remove_args(struct xfs_da_args *args);
+int xfs_attr_remove_iter(struct xfs_delattr_context *dac);
 bool xfs_attr_namecheck(const void *name, size_t length);
 
 #endif	/* __XFS_ATTR_H__ */