From 67be54fb64cfcd63dfe3638c507aa7f29bd86ec5 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Wed, 15 Oct 2025 13:43:39 -0400
Subject: kern: vfs: Make vnode r/w operations offset aware

Adds offset handling to the vnode read and write callbacks.

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 src/sys/include/os/filedesc.h |  2 ++
 src/sys/include/os/vnode.h    |  8 ++++++--
 src/sys/os/os_filedes.c       | 21 ++++++++++++++++++---
 src/sys/os/vfs_subr.c         |  6 ++++--
 4 files changed, 30 insertions(+), 7 deletions(-)

(limited to 'src')

diff --git a/src/sys/include/os/filedesc.h b/src/sys/include/os/filedesc.h
index 8cdf161..fb899cf 100644
--- a/src/sys/include/os/filedesc.h
+++ b/src/sys/include/os/filedesc.h
@@ -39,11 +39,13 @@ struct proc;
  * Represents a file descriptor
  *
  * @fdno: File descriptor index
+ * @off: Current file offset
  * @vp: Vnode this fd is linked with
  * @mode: File attributes
  */
 struct filedesc {
     int fdno;
+    off_t off;
     struct vnode *vp;
     mode_t mode;
 };
diff --git a/src/sys/include/os/vnode.h b/src/sys/include/os/vnode.h
index 868e137..9054a55 100644
--- a/src/sys/include/os/vnode.h
+++ b/src/sys/include/os/vnode.h
@@ -72,11 +72,13 @@ struct vop_lookup_args {
  *
  * @data: Buffer containing I/O data
  * @len: Length of buffer
+ * @off: Offset of operation
  * @vp: Current vnode
  */
 struct vop_rw_data {
     void *data;
     size_t len;
+    off_t off;
     struct vnode *vp;
 };
 
@@ -141,23 +143,25 @@ int vfs_vrel(struct vnode *vp, int flags);
  *
  * @vp: Vnode to write to
  * @data: Data to write
+ * @off: Offset to write at
  * @len: Length of bytes to write
  *
  * Returns the number of bytes written on success, otherwise
  * a less than zero value on failure.
  */
-ssize_t vop_write(struct vnode *vp, char *data, size_t len);
+ssize_t vop_write(struct vnode *vp, char *data, off_t off, size_t len);
 
 /*
  * Wrapper for the read write callback
  *
  * @vp: Vnode to read from
  * @data: Read data written here
+ * @off: Offset to read at
  * @len: Length of bytes to read
  *
  * Returns the number of bytes read on success, otherwise
  * a less than zero value on failure.
  */
-ssize_t vop_read(struct vnode *vp, char *data, size_t len);
+ssize_t vop_read(struct vnode *vp, char *data, off_t off, size_t len);
 
 #endif  /* !_OS_VNODE_H_ */
diff --git a/src/sys/os/os_filedes.c b/src/sys/os/os_filedes.c
index 9ba0c63..948bad2 100644
--- a/src/sys/os/os_filedes.c
+++ b/src/sys/os/os_filedes.c
@@ -227,8 +227,9 @@ write(int fd, const void *buf, size_t count)
 {
     struct proc *self = proc_self();
     struct filedesc *fdp;
-    int error;
+    ssize_t retval;
     char kbuf[1024];
+    int error;
 
     if (self == NULL) {
         return -ESRCH;
@@ -267,7 +268,13 @@ write(int fd, const void *buf, size_t count)
         if (fdp->vp == NULL) {
             return -EIO;
         }
-        return vop_write(fdp->vp, kbuf, count);
+        retval = vop_write(fdp->vp, kbuf, fdp->off, count);
+        if (retval <= 0) {
+            return retval;
+        }
+
+        /* Move away from where we wrote */
+        fdp->off += count;
     }
 
     return count;
@@ -278,6 +285,7 @@ read(int fd, void *buf, size_t count)
 {
     struct proc *self = proc_self();
     struct filedesc *fdp;
+    ssize_t retval;
     int error;
 
     if (buf == NULL) {
@@ -304,7 +312,14 @@ read(int fd, void *buf, size_t count)
         return -EIO;
     }
 
-    return vop_read(fdp->vp, buf, count);
+    /* Read the file */
+    retval = vop_read(fdp->vp, buf, fdp->off, count);
+    if (retval <= 0) {
+        return retval;
+    }
+
+    fdp->off += count;
+    return retval;
 }
 
 /*
diff --git a/src/sys/os/vfs_subr.c b/src/sys/os/vfs_subr.c
index 47ed468..a06b64f 100644
--- a/src/sys/os/vfs_subr.c
+++ b/src/sys/os/vfs_subr.c
@@ -145,7 +145,7 @@ vfs_cmp_cnt(const char *path)
 }
 
 ssize_t
-vop_write(struct vnode *vp, char *data, size_t len)
+vop_write(struct vnode *vp, char *data, off_t off, size_t len)
 {
     struct vop_rw_data rwdata;
     struct vop *vops;
@@ -170,11 +170,12 @@ vop_write(struct vnode *vp, char *data, size_t len)
     rwdata.data = data;
     rwdata.len = len;
     rwdata.vp = vp;
+    rwdata.off = off;
     return vops->write(&rwdata);
 }
 
 ssize_t
-vop_read(struct vnode *vp, char *data, size_t len)
+vop_read(struct vnode *vp, char *data, off_t off, size_t len)
 {
     struct vop_rw_data rwdata;
     struct vop *vops;
@@ -199,5 +200,6 @@ vop_read(struct vnode *vp, char *data, size_t len)
     rwdata.data = data;
     rwdata.len = len;
     rwdata.vp = vp;
+    rwdata.off = off;
     return vops->read(&rwdata);
 }
-- 
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