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

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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: Chenghao Duan <duanchenghao@kylinos.cn>
Suggested-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Haoran Jiang <jianghaoran@kylinos.cn>
Cc: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Chenghao Duan
2026-03-26 16:47:21 +08:00
committed by Andrew Morton
parent 7cf6d940f4
commit ed2a29dc6d
1 changed files with 6 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
mm/memfd_luo.c
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@@ -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);