On Tue, 13 Jul 2021 18:30:18, Jan Kara wrote:

On Tue 13-07-21 16:59:18, Javier Pello wrote:

quoted

Commit 782b76d7abdf02b12c46ed6f1e9bf715569027f7 ("fs/ext2: Replace
kmap() with kmap_local_page()") replaced the kmap/kunmap calls in
ext2_get_page/ext2_put_page with kmap_local_page/kunmap_local for
efficiency reasons. As a necessary side change, the commit also
made ext2_get_page (and ext2_find_entry and ext2_dotdot) return
the mapping address along with the page itself, as it is required
for kunmap_local, and converted uses of page_address on such pages
to use the newly returned address instead. However, uses of
page_address on such pages were missed in ext2_check_page and
ext2_delete_entry, which triggers oopses if kmap_local_page happens
to return an address from high memory. Fix this now by converting
the remaining uses of page_address to use the right address, as
returned by kmap_local_page.

Good catch. Thanks for the patch. Ira, can you please check the patch as
well?

I have just a few nits below:

quoted

Signed-off-by: Javier Pello <redacted>
Fixes: 782b76d7abdf fs/ext2: Replace kmap() with kmap_local_page()

Please wrap subject in Fixes tag into ("...").

Will do.

quoted

@@ -584,16 +584,16 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode)
  * ext2_delete_entry deletes a directory entry by merging it with the
  * previous entry. Page is up-to-date.
  */
-int ext2_delete_entry (struct ext2_dir_entry_2 * dir, struct page * page )
+int ext2_delete_entry (struct ext2_dir_entry_2 *dir, struct page *page,
+                     void *kaddr)

Why not have 'kaddr' as char *. We type it to char * basically everywhere
anyway.

I thought about that, as well, but in the end I leaned towards void *
because it is a generic pointer, conceptually. Would you rather have it
be char *?

quoted

 {
      struct inode *inode = page->mapping->host;
-     char *kaddr = page_address(page);
-     unsigned from = ((char*)dir - kaddr) & ~(ext2_chunk_size(inode)-1);
-     unsigned to = ((char *)dir - kaddr) +
-                             ext2_rec_len_from_disk(dir->rec_len);
+     unsigned int delta = (char *)dir - (char *)kaddr;

Maybe I'd call this 'offset' rather than 'delta'.

Fair enough.

Also if kaddr will stay
char *, you maybe just don't need to touch this...

Yes, if kaddr becomes char * then there is no need to touch these lines.

Javier