Second Extended Filesystem (ext2) and other improvements (#33)

[lunaix-os.git] / lunaix-os / kernel / block / blkio.c

diff --git a/lunaix-os/kernel/block/blkio.c b/lunaix-os/kernel/block/blkio.c
index bc0178c1be562c014fbee93b19979f94e7219c5c..481092558da302ecce59ba891174af3e5db432c3 100644 (file)
--- a/lunaix-os/kernel/block/blkio.c
+++ b/lunaix-os/kernel/block/blkio.c
@@ -1,9 +1,14 @@
 #include <lunaix/blkio.h>
+#include <lunaix/syslog.h>
 #include <lunaix/mm/cake.h>
 #include <lunaix/mm/valloc.h>
 
+#include <sys/cpu.h>
+
 static struct cake_pile* blkio_reqpile;
 
+LOG_MODULE("blkio")
+
 void
 blkio_init()
 {
@@ -65,28 +70,88 @@ blkio_newctx(req_handler handler)
     ctx->handle_one = handler;
 
     llist_init_head(&ctx->queue);
+    mutex_init(&ctx->lock);
 
     return ctx;
 }
 
 void
-blkio_commit(struct blkio_context* ctx, struct blkio_req* req)
+blkio_commit(struct blkio_req* req, int options)
 {
+    struct blkio_context* ctx;
+
+    if (blkio_is_pending(req)) {
+        // prevent double submition
+        return;
+    }
+
+    assert(req->io_ctx);
+
     req->flags |= BLKIO_PENDING;
-    req->io_ctx = ctx;
-    llist_append(&ctx->queue, &req->reqs);
+    
+    if ((options & BLKIO_WAIT)) {
+        req->flags |= BLKIO_SHOULD_WAIT;
+        prepare_to_wait(&req->wait);
+    }
+    else {
+        req->flags &= ~BLKIO_SHOULD_WAIT;
+    }
+
+    ctx = req->io_ctx;
 
+    blkio_lock(ctx);
+    
+    llist_append(&ctx->queue, &req->reqs);
+    
+    blkio_unlock(ctx);
     // if the pipeline is not running (e.g., stalling). Then we should schedule
     // one immediately and kick it started.
-    if (!ctx->busy) {
+    // NOTE: Possible race condition between blkio_commit and pwait.
+    // Consider: what if scheduler complete the request before pwait even get
+    // called?
+    // Two possible work around:
+    //  #1. we disable the interrupt before schedule the request.
+    //  #2. we do scheduling within interrupt context (e.g., attach a timer)
+    // As we don't want to overwhelming the interrupt context and also keep the
+    // request RTT as small as possible, hence #1 is preferred.
+
+    /*
+        FIXME
+        Potential racing here.
+        happened when blkio is committed at high volumn, while the
+         block device has very little latency.
+        This is particular serious for non-async blkio, it could
+         completed before we do pwait, causing the thread hanged indefinitely
+    */
+
+    if (blkio_stalled(ctx)) {
+        if ((options & BLKIO_WAIT)) {
+            blkio_schedule(ctx);
+            try_wait_check_stall();
+            return;
+        }
         blkio_schedule(ctx);
+    } else if ((options & BLKIO_WAIT)) {
+        try_wait_check_stall();
     }
 }
 
 void
 blkio_schedule(struct blkio_context* ctx)
 {
+    // stall the pipeline if ctx is locked by others.
+    // we must not try to hold the lock in this case, as
+    //  blkio_schedule will be in irq context most of the
+    //  time, we can't afford the waiting there.
+    if (mutex_on_hold(&ctx->lock)) {
+        return;
+    }
+
+    // will always successed when in irq context
+    blkio_lock(ctx);
+
     if (llist_empty(&ctx->queue)) {
+        blkio_unlock(ctx);
         return;
     }
 
@@ -94,7 +159,9 @@ blkio_schedule(struct blkio_context* ctx)
     llist_delete(&head->reqs);
 
     head->flags |= BLKIO_BUSY;
-    head->io_ctx->busy++;
+    ctx->busy++;
+
+    blkio_unlock(ctx);
 
     ctx->handle_one(head);
 }
@@ -102,21 +169,30 @@ blkio_schedule(struct blkio_context* ctx)
 void
 blkio_complete(struct blkio_req* req)
 {
+    struct blkio_context* ctx;
+
+    ctx = req->io_ctx;
     req->flags &= ~(BLKIO_BUSY | BLKIO_PENDING);
 
+    // Wake all blocked processes on completion,
+    //  albeit should be no more than one process in everycase (by design)
+    if ((req->flags & BLKIO_SHOULD_WAIT)) {
+        assert(!waitq_empty(&req->wait));
+        pwake_all(&req->wait);
+    }
+
+    if (req->errcode) {
+        WARN("request completed with error. (errno=0x%x, ctx=%p)",
+                req->errcode, (ptr_t)ctx);
+    }
+
     if (req->completed) {
         req->completed(req);
     }
 
-    // Wake all blocked processes on completion,
-    //  albeit should be no more than one process in everycase (by design)
-    pwake_all(&req->wait);
-
     if ((req->flags & BLKIO_FOC)) {
         blkio_free_req(req);
     }
 
-    req->io_ctx->busy--;
-
-    blkio_schedule(req->io_ctx);
+    ctx->busy--;
 }
\ No newline at end of file