[PATCH v2 14/29] tools/xenlogd: add 9pfs read request support

[Juergen Gross <jgross@xxxxxxxx>]

Add the read request of the 9pfs protocol.

For now support only reading plain files (no directories).

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Jason Andryuk <jandryuk@xxxxxxxxx>
---
V2:
- make error check more readable (Jason Andryuk)
---
 tools/xen-9pfsd/io.c | 64 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)

diff --git a/tools/xen-9pfsd/io.c b/tools/xen-9pfsd/io.c
index f8d981c2a6..1edea2e24a 100644
--- a/tools/xen-9pfsd/io.c
+++ b/tools/xen-9pfsd/io.c
@@ -32,6 +32,7 @@
 #define P9_CMD_WALK       110
 #define P9_CMD_OPEN       112
 #define P9_CMD_CREATE     114
+#define P9_CMD_READ       116
 #define P9_CMD_WRITE      118
 #define P9_CMD_CLUNK      120
 #define P9_CMD_STAT       124
@@ -1120,6 +1121,65 @@ static void p9_create(struct ring *ring, struct 
p9_header *hdr)
     free_fid(device, fidp);
 }
 
+static void p9_read(struct ring *ring, struct p9_header *hdr)
+{
+    device *device = ring->device;
+    uint32_t fid;
+    uint64_t off;
+    unsigned int len;
+    uint32_t count;
+    void *buf;
+    struct p9_fid *fidp;
+    int ret;
+
+    ret = fill_data(ring, "ULU", &fid, &off, &count);
+    if ( ret != 3 )
+    {
+        p9_error(ring, hdr->tag, EINVAL);
+        return;
+    }
+
+    fidp = get_fid_ref(device, fid);
+    if ( !fidp || !fidp->opened )
+    {
+        p9_error(ring, hdr->tag, EBADF);
+        goto out;
+    }
+
+    if ( fidp->isdir )
+    {
+        p9_error(ring, hdr->tag, EOPNOTSUPP);
+        goto out;
+    }
+    else
+    {
+        len = count;
+        buf = ring->buffer + sizeof(*hdr) + sizeof(uint32_t);
+
+        while ( len != 0 )
+        {
+            ret = pread(fidp->fd, buf, len, off);
+            if ( ret <= 0 )
+                break;
+            len -= ret;
+            buf += ret;
+            off += ret;
+        }
+        if ( ret < 0 && len == count )
+        {
+            p9_error(ring, hdr->tag, errno);
+            goto out;
+        }
+
+        buf = ring->buffer + sizeof(*hdr) + sizeof(uint32_t);
+        len = count - len;
+        fill_buffer(ring, hdr->cmd + 1, hdr->tag, "D", &len, buf);
+    }
+
+ out:
+    free_fid(device, fidp);
+}
+
 static void p9_write(struct ring *ring, struct p9_header *hdr)
 {
     device *device = ring->device;
@@ -1349,6 +1409,10 @@ void *io_thread(void *arg)
                 p9_create(ring, &hdr);
                 break;
 
+            case P9_CMD_READ:
+                p9_read(ring, &hdr);
+                break;
+
             case P9_CMD_WRITE:
                 p9_write(ring, &hdr);
                 break;
-- 
2.35.3