[Minios-devel] [UNIKRAFT PATCH v3 4/5] lib/vfscore: do not advance position for stdio

[Yuri Volchkov <yuri.volchkov@xxxxxxxxx>]

With the proper handling of uio for stdio files, vfs also advances the
position in the struct file. Which does not make any sense for console
(and some other classes of devices).

This patch adds another flags variable inside struct
vfscore_file. Using f_flags would add more mess in the code, because
most of the flags are defined in fcntl.h, which is external from
vfscore header.

Signed-off-by: Yuri Volchkov <yuri.volchkov@xxxxxxxxx>
Signed-off-by: Vlad-Andrei Badoiu <vlad_andrei.badoiu@xxxxxxxxxxxxxxx>
---
 lib/vfscore/fops.c                 | 6 ++++--
 lib/vfscore/include/vfscore/file.h | 6 ++++++
 lib/vfscore/stdio.c                | 1 +
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/lib/vfscore/fops.c b/lib/vfscore/fops.c
index 79114e21..8f5c2e1b 100644
--- a/lib/vfscore/fops.c
+++ b/lib/vfscore/fops.c
@@ -75,7 +75,8 @@ int vfs_read(struct vfscore_file *fp, struct uio *uio, int 
flags)
        error = VOP_READ(vp, fp, uio, 0);
        if (!error) {
                count = bytes - uio->uio_resid;
-               if ((flags & FOF_OFFSET) == 0)
+               if (((flags & FOF_OFFSET) == 0) &&
+                   !(fp->f_vfs_flags & UK_VFSCORE_NOPOS))
                        fp->f_offset += count;
        }
        vn_unlock(vp);
@@ -107,7 +108,8 @@ int vfs_write(struct vfscore_file *fp, struct uio *uio, int 
flags)
        error = VOP_WRITE(vp, uio, ioflags);
        if (!error) {
                count = bytes - uio->uio_resid;
-               if ((flags & FOF_OFFSET) == 0)
+               if (!(flags & FOF_OFFSET) &&
+                   !(fp->f_vfs_flags & UK_VFSCORE_NOPOS))
                        fp->f_offset += count;
        }
 
diff --git a/lib/vfscore/include/vfscore/file.h 
b/lib/vfscore/include/vfscore/file.h
index 2c0252e2..e602d32d 100644
--- a/lib/vfscore/include/vfscore/file.h
+++ b/lib/vfscore/include/vfscore/file.h
@@ -46,12 +46,18 @@ extern "C" {
 
 struct vfscore_file;
 
+/* Set this flag if vfs should NOt hande POSition for this file. The
+ * file is not seek-able, updating f_offset does not make sense for
+ * it */
+#define UK_VFSCORE_NOPOS ((int) (1 << 0))
+
 struct vfscore_file {
        int fd;
        int             f_flags;        /* open flags */
        int             f_count;        /* reference count */
        off_t           f_offset;       /* current position in file */
        void            *f_data;        /* file descriptor specific data */
+       int             f_vfs_flags;    /* internal implementation flags */
        struct dentry   *f_dentry;
 };
 
diff --git a/lib/vfscore/stdio.c b/lib/vfscore/stdio.c
index 56c11a92..bd814fa0 100644
--- a/lib/vfscore/stdio.c
+++ b/lib/vfscore/stdio.c
@@ -149,6 +149,7 @@ static struct vfscore_file  stdio_file = {
        .fd = 1,
        .f_flags = UK_FWRITE | UK_FREAD,
        .f_dentry = &stdio_dentry,
+       .f_vfs_flags = UK_VFSCORE_NOPOS,
        /* reference count is 2 because close(0) is a valid
         * operation. However it is not properly handled in the
         * current implementation. */
-- 
2.19.2


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