pipe: first cut at fixing a pile of pipe breakages

There is still lots more to deal with

- introduce a helper to check if a file is open for read/write
- use this to correct the EOF checking

Original bugs noted by David Flamand

diff --git a/Kernel/filesys.c b/Kernel/filesys.c
index 57ac39c..2dfdde6 100644 (file)
--- a/Kernel/filesys.c
+++ b/Kernel/filesys.c
@@ -687,6 +687,21 @@ int8_t oft_alloc(void)
     return -1;
 }
 
+/*     Check if an inode is open for reading or for writing. Needed for pipe
+ *     EOF and will one day be needed for shared code segments (8086 etc)
+ */
+int8_t oft_inuse(inoptr ino, uint8_t rw)
+{
+    struct oft *ofptr = of_tab;
+    while(ofptr <= &of_tab[OFTSIZE - 1]) {
+        if (ofptr->o_refs && ofptr->o_inode == ino &&
+            O_ACCMODE(ofptr->o_access) != rw)
+            return 1;
+        ofptr++;
+    }
+    return 0;
+}
+
 /*
  *     To minimise storage we don't track exclusive locks explicitly. We know
  *     that if we are dropping an exclusive lock then we must be the owner,

diff --git a/Kernel/include/kernel.h b/Kernel/include/kernel.h
index c9a000e..01e5e00 100644 (file)
--- a/Kernel/include/kernel.h
+++ b/Kernel/include/kernel.h
@@ -776,6 +776,11 @@ extern void i_free(uint16_t devno, uint16_t ino);
 extern blkno_t blk_alloc(uint16_t devno);
 extern void blk_free(uint16_t devno, blkno_t blk);
 extern int8_t oft_alloc(void);
+extern int8_t oft_inuse(inoptr ino, uint8_t rw);
+/* Yes these are intentionally backwards - there are 3 modes so the loop looks
+   for "not this mode" */
+#define INUSE_R                O_WRONLY
+#define INUSE_W                O_RDONLY
 extern void deflock(struct oft *ofptr);
 extern void oft_deref(int8_t of);
 /* returns index of slot, or -1 on failure */

diff --git a/Kernel/inode.c b/Kernel/inode.c
index 1c590db..dc0f2ac 100644 (file)
--- a/Kernel/inode.c
+++ b/Kernel/inode.c
@@ -10,6 +10,23 @@
 #define read_direct(flag)              (flag & O_DIRECT)
 #endif
 
+/* This assumes it's called once before we do I/O. That's wrong and we
+   need to integrate this into the I/O loop, but when we do it changes
+   how we handle the psleep_flags bit */
+static uint8_t pipewait(inoptr ino, uint8_t flag)
+{
+        int8_t n;
+        while(ino->c_node.i_size == 0) {
+                n = oft_inuse(ino, INUSE_W);
+                if (n == 0 || psleep_flags(ino, flag)) {
+                        udata.u_count = 0;
+                        return 0;
+                }
+        }
+       udata.u_count = min(udata.u_count, ino->c_node.i_size);
+        return 1;
+}
+
 /* Writei (and readi) need more i/o error handling */
 void readi(inoptr ino, uint8_t flag)
 {
@@ -33,7 +50,6 @@ void readi(inoptr ino, uint8_t flag)
                        udata.u_count = min(udata.u_count,
                                ino->c_node.i_size - udata.u_offset);
                 }
-               toread = udata.u_count;
                goto loop;
 
         case MODE_R(F_SOCK):
@@ -43,25 +59,16 @@ void readi(inoptr ino, uint8_t flag)
 #endif
        case MODE_R(F_PIPE):
                ispipe = true;
-               while (ino->c_node.i_size == 0 && !(flag & O_NDELAY)) {
-                       if (ino->c_refs == 1)   /* No writers */
-                               break;
-                       /* Sleep if empty pipe */
-                       if (psleep_flags(ino, flag))
-                               break;
-               }
-               toread = udata.u_count = min(udata.u_count, ino->c_node.i_size);
-               if (toread == 0) {
-                       udata.u_error = EWOULDBLOCK;
-                       break;
-               }
+               /* This bit really needs to be inside the loop for pipe cases */
+               if (!pipewait(ino, flag))
+                       break;
                goto loop;
 
        case MODE_R(F_BDEV):
-               toread = udata.u_count;
                dev = *(ino->c_node.i_addr);
 
              loop:
+               toread = udata.u_count;
                while (toread) {
                        amount = min(toread, BLKSIZE - BLKOFF(udata.u_offset));
                        pblk = bmap(ino, udata.u_offset >> BLKSHIFT, 1);
@@ -157,7 +164,7 @@ void writei(inoptr ino, uint8_t flag)
                   in one go - needs merging into the loop */
                while ((towrite = udata.u_count) > (16 * BLKSIZE) - 
                                        ino->c_node.i_size) {
-                       if (ino->c_refs == 1) { /* No readers */
+                       if (!oft_inuse(ino, INUSE_R)) { /* No readers */
                                udata.u_count = (usize_t)-1;
                                udata.u_error = EPIPE;
                                ssig(udata.u_ptab, SIGPIPE);