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 kv5IiE+I QxGnTjsrCegSFBa8nb2XzZN2dXt1dQY88daeX5mB+YOHVIflFiq6a2Z+o5ima5eHSgri/lQzWL98tg4J7E4sevzMbXEBzCveJerKXkg6Qy7XG3M/4nCZoGnKh7P/NccUw9AZSVqgaoS6wwjKMOvWqBzoUzWNV/qDieyy43qqIvWq8aJdoS0RI1i1oiYAPqXoKCEgdG1jpHOlS47CSje6nb7zoZkTWroQNn9eap8gswnTVM0LxUmcPYZwl7JoqaFec7PrLyEfaowYG0d8= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Jan Kara wrote: > On Thu 11-04-24 10:57:25, Alistair Popple wrote: > > The page->mapping and page->index fields are normally used by the > > pagecache and rmap for looking up virtual mappings of pages. FS DAX > > implements it's own kind of page cache and rmap look ups so these > > fields are unnecessary. They are currently only used to detect > > error/warning conditions which should never occur. > > > > A future change will change the way shared mappings are detected by > > doing normal page reference counting instead, so remove the > > unnecessary checks. > > > > Signed-off-by: Alistair Popple > ... > > -/* > > - * When it is called in dax_insert_entry(), the shared flag will indicate that > > - * whether this entry is shared by multiple files. If so, set the page->mapping > > - * PAGE_MAPPING_DAX_SHARED, and use page->share as refcount. > > - */ > > -static void dax_associate_entry(void *entry, struct address_space *mapping, > > - struct vm_area_struct *vma, unsigned long address, bool shared) > > -{ > > - unsigned long size = dax_entry_size(entry), pfn, index; > > - int i = 0; > > - > > - if (IS_ENABLED(CONFIG_FS_DAX_LIMITED)) > > - return; > > - > > - index = linear_page_index(vma, address & ~(size - 1)); > > - for_each_mapped_pfn(entry, pfn) { > > - struct page *page = pfn_to_page(pfn); > > - > > - if (shared) { > > - dax_page_share_get(page); > > - } else { > > - WARN_ON_ONCE(page->mapping); > > - page->mapping = mapping; > > - page->index = index + i++; > > - } > > - } > > -} > > Hum, but what about existing uses of folio->mapping and folio->index in > fs/dax.c? AFAICT this patch breaks them. What am I missing? How can this > ever work? Right, as far as I can see every fsdax filesystem would need to be converted to use dax_holder_operations() so that the fs can backfill ->mapping and ->index.