[PATCH v3 3/7] Mini-OS: add support for runtime mounts

[Juergen Gross]

Add the support to mount a device at runtime. The number of dynamic
mounts is limited by a #define.

For devices supporting multiple files struct file is modified to hold
a pointer to file specific data in contrast to device specific data.

Signed-off-by: Juergen Gross <jgr...@suse.com>
Reviewed-by: Samuel Thibault <samuel.thiba...@ens-lyon.org>
---
V3:
- set number of possible mountpoints to 16 (Andrew Cooper)
---
 include/lib.h |  5 +++++
 lib/sys.c     | 45 ++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/include/lib.h b/include/lib.h
index 36d94ec4..fd8c36de 100644
--- a/include/lib.h
+++ b/include/lib.h
@@ -172,6 +172,7 @@ struct file {
     union {
         int fd; /* Any fd from an upper layer. */
         void *dev;
+        void *filedata;
     };
 };
 
@@ -194,6 +195,10 @@ struct mount_point {
     void *dev;
 };
 
+int mount(const char *path, void *dev,
+          int (*open)(struct mount_point *, const char *, int, mode_t));
+void umount(const char *path);
+
 unsigned int alloc_file_type(const struct file_ops *ops);
 
 off_t lseek_default(struct file *file, off_t offset, int whence);
diff --git a/lib/sys.c b/lib/sys.c
index 2f33c937..118fc441 100644
--- a/lib/sys.c
+++ b/lib/sys.c
@@ -85,6 +85,8 @@
     }
 
 #define NOFILE 32
+#define N_MOUNTS  16
+
 extern void minios_evtchn_close_fd(int fd);
 extern void minios_gnttab_close_fd(int fd);
 
@@ -339,7 +341,7 @@ static int open_mem(struct mount_point *mnt, const char 
*pathname, int flags,
     return fd;
 }
 
-static struct mount_point mount_points[] = {
+static struct mount_point mount_points[N_MOUNTS] = {
     { .path = "/var/log",     .open = open_log,  .dev = NULL },
     { .path = "/dev/mem",     .open = open_mem,  .dev = NULL },
 #ifdef CONFIG_CONSFRONT
@@ -365,6 +367,8 @@ int open(const char *pathname, int flags, ...)
     for ( m = 0; m < ARRAY_SIZE(mount_points); m++ )
     {
         mnt = mount_points + m;
+        if ( !mnt->path )
+            continue;
         mlen = strlen(mnt->path);
         if ( !strncmp(pathname, mnt->path, mlen) &&
              (pathname[mlen] == '/' || pathname[mlen] == 0) )
@@ -375,6 +379,45 @@ int open(const char *pathname, int flags, ...)
     return -1;
 }
 
+int mount(const char *path, void *dev,
+          int (*open)(struct mount_point *, const char *, int, mode_t))
+{
+    unsigned int m;
+    struct mount_point *mnt;
+
+    for ( m = 0; m < ARRAY_SIZE(mount_points); m++ )
+    {
+        mnt = mount_points + m;
+        if ( !mnt->path )
+        {
+            mnt->path = strdup(path);
+            mnt->open = open;
+            mnt->dev = dev;
+            return 0;
+        }
+    }
+
+    errno = ENOSPC;
+    return -1;
+}
+
+void umount(const char *path)
+{
+    unsigned int m;
+    struct mount_point *mnt;
+
+    for ( m = 0; m < ARRAY_SIZE(mount_points); m++ )
+    {
+        mnt = mount_points + m;
+        if ( mnt->path && !strcmp(mnt->path, path) )
+        {
+            free((char *)mnt->path);
+            mnt->path = NULL;
+            return;
+        }
+    }
+}
+
 int isatty(int fd)
 {
     return files[fd].type == FTYPE_CONSOLE;
-- 
2.35.3