Commit ed2a29dc authored by Chenghao Duan's avatar Chenghao Duan Committed by Andrew Morton
Browse files

mm/memfd: use folio_nr_pages() for shmem inode accounting 

I found several modifiable points while reading the code.


This patch (of 6):

Patch series "Modify memfd_luo code", v3.

memfd_luo_retrieve_folios() called shmem_inode_acct_blocks() and
shmem_recalc_inode() with hardcoded 1 instead of the actual folio page
count.  memfd may use large folios (THP/hugepages), causing quota/limit
under-accounting and incorrect stat output.

Fix by using folio_nr_pages(folio) for both functions.

Issue found by AI review and suggested by Pratyush Yadav <pratyush@kernel.org>.
https://sashiko.dev/#/patchset/20260319012845.29570-1-duanchenghao%40kylinos.cn

Link: https://lore.kernel.org/20260326084727.118437-1-duanchenghao@kylinos.cn
Link: https://lore.kernel.org/20260326084727.118437-2-duanchenghao@kylinos.cn


Signed-off-by: default avatarChenghao Duan <duanchenghao@kylinos.cn>
Suggested-by: default avatarPratyush Yadav <pratyush@kernel.org>
Reviewed-by: default avatarPasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: default avatarPratyush Yadav <pratyush@kernel.org>
Cc: Haoran Jiang <jianghaoran@kylinos.cn>
Cc: Mike Rapoport <rppt@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 7cf6d940

mm/memfd_luo.c

+6 −4
Original line number Diff line number Diff line
@@ -410,6 +410,7 @@ static int memfd_luo_retrieve_folios(struct file *file, 
	struct inode *inode = file_inode(file);

	struct address_space *mapping = inode->i_mapping;

	struct folio *folio;

	long npages;

	int err = -EIO;

	long i;
@@ -456,14 +457,15 @@ static int memfd_luo_retrieve_folios(struct file *file, 
		if (flags & MEMFD_LUO_FOLIO_DIRTY)

			folio_mark_dirty(folio);



		err = shmem_inode_acct_blocks(inode, 1);

		npages = folio_nr_pages(folio);

		err = shmem_inode_acct_blocks(inode, npages);

		if (err) {

			pr_err("shmem: failed to account folio index %ld: %d\n",

			       i, err);

			pr_err("shmem: failed to account folio index %ld(%ld pages): %d\n",

			       i, npages, err);

			goto unlock_folio;

		}



		shmem_recalc_inode(inode, 1, 0);

		shmem_recalc_inode(inode, npages, 0);

		folio_add_lru(folio);

		folio_unlock(folio);

		folio_put(folio);