For the upcoming asynchronoyus discard support we need to be able to delay
freeing the CIL context until the last discard request that reference it
has completed. Add a reference count to the CIL context, and only clear
the busy extents and free the CIL context structure when it reaches zero,
and a work item to allow freeing it from irq context.
Note that this means delaying the clearing of the busy extents for a little
bit even on non-discard mounts, but with the new busy extent trim/reuse
code there is no real life impact of this change.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Index: xfs/fs/xfs/xfs_log_cil.c
===================================================================
--- xfs.orig/fs/xfs/xfs_log_cil.c 2011-03-28 15:41:39.062838900 +0200
+++ xfs/fs/xfs/xfs_log_cil.c 2011-03-28 16:47:04.658839185 +0200
@@ -30,6 +30,46 @@
#include "xfs_error.h"
#include "xfs_alloc.h"
+static void
+xlog_cil_ctx_free(
+ struct xfs_cil_ctx *ctx)
+{
+ struct xfs_busy_extent *busyp, *n;
+
+ list_for_each_entry_safe(busyp, n, &ctx->busy_extents, list)
+ xfs_alloc_busy_clear(ctx->cil->xc_log->l_mp, busyp);
+ kmem_free(ctx);
+}
+
+static void
+xlog_cil_ctx_free_work(
+ struct work_struct *work)
+{
+ xlog_cil_ctx_free(container_of(work, struct xfs_cil_ctx, work));
+}
+
+static void
+xlog_cil_ctx_init(
+ struct xfs_cil_ctx *ctx,
+ struct xfs_cil *cil,
+ xfs_lsn_t sequence)
+{
+ INIT_LIST_HEAD(&ctx->committing);
+ INIT_LIST_HEAD(&ctx->busy_extents);
+ ctx->sequence = sequence;
+ ctx->cil = cil;
+ atomic_set(&ctx->ref, 1);
+ INIT_WORK(&ctx->work, xlog_cil_ctx_free_work);
+ cil->xc_ctx = ctx;
+
+ /*
+ * Mirror the sequence into the cil structure so that we can do
+ * unlocked checks against the current sequence in log forces without
+ * risking deferencing a freed context pointer.
+ */
+ cil->xc_current_sequence = ctx->sequence;
+}
+
/*
* Perform initial CIL structure initialisation. If the CIL is not
* enabled in this filesystem, ensure the log->l_cilp is null so
@@ -63,12 +103,7 @@ xlog_cil_init(
init_rwsem(&cil->xc_ctx_lock);
init_waitqueue_head(&cil->xc_commit_wait);
- INIT_LIST_HEAD(&ctx->committing);
- INIT_LIST_HEAD(&ctx->busy_extents);
- ctx->sequence = 1;
- ctx->cil = cil;
- cil->xc_ctx = ctx;
- cil->xc_current_sequence = ctx->sequence;
+ xlog_cil_ctx_init(ctx, cil, 1);
cil->xc_log = log;
log->l_cilp = cil;
@@ -361,20 +396,17 @@ xlog_cil_committed(
int abort)
{
struct xfs_cil_ctx *ctx = args;
- struct xfs_busy_extent *busyp, *n;
xfs_trans_committed_bulk(ctx->cil->xc_log->l_ailp, ctx->lv_chain,
ctx->start_lsn, abort);
- list_for_each_entry_safe(busyp, n, &ctx->busy_extents, list)
- xfs_alloc_busy_clear(ctx->cil->xc_log->l_mp, busyp);
-
spin_lock(&ctx->cil->xc_cil_lock);
list_del(&ctx->committing);
spin_unlock(&ctx->cil->xc_cil_lock);
xlog_cil_free_logvec(ctx->lv_chain);
- kmem_free(ctx);
+ if (atomic_dec_and_test(&ctx->ref))
+ xlog_cil_ctx_free(ctx);
}
/*
@@ -481,18 +513,7 @@ xlog_cil_push(
* during log forces to extract the commit lsn of the sequence that
* needs to be forced.
*/
- INIT_LIST_HEAD(&new_ctx->committing);
- INIT_LIST_HEAD(&new_ctx->busy_extents);
- new_ctx->sequence = ctx->sequence + 1;
- new_ctx->cil = cil;
- cil->xc_ctx = new_ctx;
-
- /*
- * mirror the new sequence into the cil structure so that we can do
- * unlocked checks against the current sequence in log forces without
- * risking deferencing a freed context pointer.
- */
- cil->xc_current_sequence = new_ctx->sequence;
+ xlog_cil_ctx_init(new_ctx, cil, ctx->sequence + 1);
/*
* The switch is now done, so we can drop the context lock and move out
Index: xfs/fs/xfs/xfs_log_priv.h
===================================================================
--- xfs.orig/fs/xfs/xfs_log_priv.h 2011-03-28 16:06:20.398888649 +0200
+++ xfs/fs/xfs/xfs_log_priv.h 2011-03-28 16:47:04.662839297 +0200
@@ -389,6 +389,8 @@ struct xfs_cil_ctx {
struct xfs_log_vec *lv_chain; /* logvecs being pushed */
xfs_log_callback_t log_cb; /* completion callback hook. */
struct list_head committing; /* ctx committing list */
+ atomic_t ref; /* reference count */
+ struct work_struct work; /* for deferred freeing */
};
/*
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