Messages in this thread Patch in this message | | | Subject | Re: [PATCH 5/4] 9p: pass the correct prototype to read_cache_page | From | William Kucharski <> | Date | Thu, 2 May 2019 00:08:29 -0600 |
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1) You need to pass "filp" rather than "filp->private_data" to read_cache_pages() in v9fs_fid_readpage().
The patched code passes "filp->private_data" as the "data" parameter to read_cache_pages(), which would generate a call to:
filler(data, page)
which would become a call to:
static int v9fs_vfs_readpage(struct file *filp, struct page *page) { return v9fs_fid_readpage(filp->private_data, page); }
which would then effectively become:
v9fs_fid_readpage(filp->private_data->private_data, page)
Which isn't correct; because data is a void *, no error is thrown when v9fs_vfs_readpages treats filp->private_data as if it is filp.
2) I'd also like to see an explicit comment in do_read_cache_page() along the lines of:
/* * If a custom page filler was passed in use it, otherwise use the * standard readpage() routine defined for the address_space. * */
3) Patch 5/4?
Otherwise it looks good.
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
> On May 1, 2019, at 11:34 AM, Christoph Hellwig <hch@lst.de> wrote: > > Fix the callback 9p passes to read_cache_page to actually have the > proper type expected. Casting around function pointers can easily > hide typing bugs, and defeats control flow protection. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > --- > fs/9p/vfs_addr.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c > index 0bcbcc20f769..02e0fc51401e 100644 > --- a/fs/9p/vfs_addr.c > +++ b/fs/9p/vfs_addr.c > @@ -50,8 +50,9 @@ > * @page: structure to page > * > */ > -static int v9fs_fid_readpage(struct p9_fid *fid, struct page *page) > +static int v9fs_fid_readpage(void *data, struct page *page) > { > + struct p9_fid *fid = data; > struct inode *inode = page->mapping->host; > struct bio_vec bvec = {.bv_page = page, .bv_len = PAGE_SIZE}; > struct iov_iter to; > @@ -122,7 +123,8 @@ static int v9fs_vfs_readpages(struct file *filp, struct address_space *mapping, > if (ret == 0) > return ret; > > - ret = read_cache_pages(mapping, pages, (void *)v9fs_vfs_readpage, filp); > + ret = read_cache_pages(mapping, pages, v9fs_fid_readpage, > + filp->private_data); > p9_debug(P9_DEBUG_VFS, " = %d\n", ret); > return ret; > }
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