[LU-19113] cfs_delete_from_page_cache() should not unlock page

• Type: Bug
• Resolution: Fixed
• Priority: Major
• Fix Version/s: Lustre 2.17.0
• Severity: 3
• Assignee: Bruno Faccini
• Reporter: Bruno Faccini

Description

cfs_delete_from_page_cache() had to be implemented because  delete_from_page_cache() Kernel external is no longer available in recent Kernels, this has started with upstream Kernel v5.16-rc4 and has been addressed by LU-16292 and fixed in associated Gerrit #49069.

Looking more closely to cfs_delete_from_page_cache() code :

/**
 * delete_from_page_cache is not exported anymore
 */
#ifdef HAVE_DELETE_FROM_PAGE_CACHE
#define cfs_delete_from_page_cache(page)        delete_from_page_cache((page))
#else
static inline void cfs_delete_from_page_cache(struct page *page)
{
        if (!page->mapping)
                return;
        LASSERT(PageLocked(page));
        get_page(page);
        unlock_page(page);
        /* on entry page is locked */
        if (S_ISREG(page->mapping->host->i_mode)) {
                generic_error_remove_folio(page->mapping, page_folio(page));
        } else {
                loff_t lstart = page->index << PAGE_SHIFT;
                loff_t lend = lstart + PAGE_SIZE - 1;


                truncate_inode_pages_range(page->mapping, lstart, lend);
        }
        lock_page(page);
        put_page(page);
}
#endif 

and also to other places where generic_error_remove_folio() is also being called, in both Lustre and Kernel, I have strong assumptions that page should not be unlocked prior to call it..., this may cause a race where page->mapping may become NULL !

I will cook a patch soon in this direction.

Issue Links

• is related to: LU-16292 ERROR: modpost: "delete_from_page_cache" undefined