From a64865a93fdb22dee230d57a0a3c684668545acd Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Tue, 1 Jul 2025 04:01:01 -0400
Subject: kernel: tmpfs: Store the *real* size in a node

The 'len' field within the tmpfs node stores the buffer length which is
relative to the tmpfs block size. Introduce a real size which returns
the amount of data actually present within those buffers.

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/fs/tmpfs.c         | 14 ++++++++++----
 sys/include/fs/tmpfs.h |  2 ++
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/sys/fs/tmpfs.c b/sys/fs/tmpfs.c
index 50f2d74..5f8e531 100644
--- a/sys/fs/tmpfs.c
+++ b/sys/fs/tmpfs.c
@@ -211,6 +211,7 @@ tmpfs_create(struct vop_create_args *args)
     root_np = TAILQ_FIRST(&root);
     np->dirvp = dirvp;
     np->type = TMPFS_REG;
+    np->real_size = 0;
     memcpy(np->rpath, pcp, strlen(pcp) + 1);
     TAILQ_INSERT_TAIL(&root_np->dirents, np, link);
 
@@ -268,6 +269,14 @@ tmpfs_write(struct vnode *vp, struct sio_txn *sio)
         np->len += TMPFS_BSIZE;
     }
 
+    /*
+     * Bring up the real size if we are writing
+     * more bytes.
+     */
+    if (sio->offset >= np->real_size) {
+        np->real_size = sio->offset;
+    }
+
     /*
      * If the length to be written exceeds the residual byte
      * count. We will try to expand the buffer by the page
@@ -315,12 +324,9 @@ tmpfs_read(struct vnode *vp, struct sio_txn *sio)
 
     spinlock_acquire(&np->lock);
 
-    if (sio->offset > np->len - 1) {
+    if (sio->offset > np->real_size) {
         return -EINVAL;
     }
-    if ((sio->offset + sio->len) > np->len) {
-        sio->len = np->len;
-    }
 
     buf = np->data;
     memcpy(sio->buf, &buf[sio->offset], sio->len);
diff --git a/sys/include/fs/tmpfs.h b/sys/include/fs/tmpfs.h
index b2a5bbe..ca24060 100644
--- a/sys/include/fs/tmpfs.h
+++ b/sys/include/fs/tmpfs.h
@@ -53,6 +53,7 @@ struct tmpfs_node;
  * @rpath: /tmp/ relative path (for lookups)
  * @type: The tmpfs node type [one-to-one to vtype]
  * @len: Length of buffer
+ * @real_size: Actual size of file
  * @data: The backing file data
  * @dirvp: Vnode of the parent node
  * @vp: Vnode of the current node
@@ -62,6 +63,7 @@ struct tmpfs_node {
     char rpath[PATH_MAX];
     uint8_t type;
     size_t len;
+    size_t real_size;
     void *data;
     struct vnode *dirvp;
     struct vnode *vp;
-- 
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