[Dazuko-devel] patch 2 for dazukofs release 3.0.0

[Lino Sanfilippo]

Bug description:
dazukofs uses the generic_file_mmap() function provided by the linux 
kernel api
to handle memory mapping. This function in turn calls the 
dazukofs_readpage()
provided by dazuko.
dazukofs_readpage() calls the readpage() operation of the address_space 
object of the
underlaying filesystems inodes. But the underlaying filesystem might not 
have initialized
this struct to provide a readpage() function (since not all filesystems 
provide memory mapping
for certain file types, i.e. directories). In this case the readpage() 
function of the address_space
object is set to NULL, resulting in an oops when dazukofs tries to call it.

The solution is not to use the generic function(s), but to provide an 
own function,
that calls the underlaying filesystems function only if it is defined.

Similar problems may occur with the generic_file_aio_read() and 
generic_file_aio_write() functions
used by dazukofs, so they have been removed, too.




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***************************************************

diff -rup dazukofs-3.0.0-p1/file.c dazukofs-3.0.0-p2/file.c
--- dazukofs-3.0.0-p1/file.c    2009-03-15 18:04:50.000000000 +0100
+++ dazukofs-3.0.0-p2/file.c    2009-03-15 18:23:53.000000000 +0100
@@ -272,6 +272,17 @@ out:
        return err;
 }
 
+static int dazukofs_mmap (struct file *file, struct vm_area_struct *vm)
+{
+       struct file *lower_file = GET_LOWER_FILE(file);
+
+       if (!lower_file || !lower_file->f_op || !lower_file->f_op->mmap) 
+               return -ENODEV;
+
+       return lower_file->f_op->mmap(file, vm); 
+}
+
+
 /**
  * Unused operations:
  *   - owner
@@ -295,18 +306,15 @@ out:
 struct file_operations dazukofs_main_fops = {
        .llseek         = dazukofs_llseek,
        .read           = dazukofs_read,
-       .aio_read       = generic_file_aio_read,
        .write          = dazukofs_write,
-       .aio_write      = generic_file_aio_write,
        .readdir        = dazukofs_readdir,
        .ioctl          = dazukofs_ioctl,
-       .mmap           = generic_file_mmap,
+       .mmap           = dazukofs_mmap,
        .open           = dazukofs_open,
        .flush          = dazukofs_flush,
        .release        = dazukofs_release,
        .fsync          = dazukofs_fsync,
        .fasync         = dazukofs_fasync,
-       .splice_read    = generic_file_splice_read,
 };
 
 /**
@@ -335,11 +343,10 @@ struct file_operations dazukofs_main_fop
 const struct file_operations dazukofs_dir_fops = {
        .readdir        = dazukofs_readdir,
        .ioctl          = dazukofs_ioctl,
-       .mmap           = generic_file_mmap,
+       .mmap           = dazukofs_mmap,
        .open           = dazukofs_open,
        .flush          = dazukofs_flush,
        .release        = dazukofs_release,
        .fsync          = dazukofs_fsync,
        .fasync         = dazukofs_fasync,
-       .splice_read    = generic_file_splice_read,
 };