| Message ID | 20230307143410.28031-6-hch@lst.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/7] mm: don't look at xarray value entries in split_huge_pages_in_file | expand |
On Tue, 7 Mar 2023, Christoph Hellwig wrote: > Use the very low level filemap_get_entry helper to look up the > entry in the xarray, and then: > > - don't bother locking the folio if only doing a userfault notification > - open code locking the page and checking for truncation in a related > code block > > This will allow to eventually remove the FGP_ENTRY flag. > > Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Hugh Dickins <hughd@google.com> but Andrew, please fold in this small improvement to its comment: [PATCH] shmem: open code the page cache lookup in shmem_get_folio_gfp fix Adjust the new comment line: shmem folio may have been swapped out. Signed-off-by: Hugh Dickins <hughd@google.com> --- mm/shmem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1905,7 +1905,7 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index, if (folio) { folio_lock(folio); - /* Has the page been truncated? */ + /* Has the folio been truncated or swapped out? */ if (unlikely(folio->mapping != mapping)) { folio_unlock(folio); folio_put(folio);
diff --git a/mm/shmem.c b/mm/shmem.c index 3705437c5757ba..714ff3fb02a938 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1856,12 +1856,10 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index, sbinfo = SHMEM_SB(inode->i_sb); charge_mm = vma ? vma->vm_mm : NULL; - folio = __filemap_get_folio(mapping, index, FGP_ENTRY | FGP_LOCK, 0); + folio = filemap_get_entry(mapping, index); if (folio && vma && userfaultfd_minor(vma)) { - if (!xa_is_value(folio)) { - folio_unlock(folio); + if (!xa_is_value(folio)) folio_put(folio); - } *fault_type = handle_userfault(vmf, VM_UFFD_MINOR); return 0; } @@ -1877,6 +1875,14 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index, } if (folio) { + folio_lock(folio); + + /* Has the page been truncated? */ + if (unlikely(folio->mapping != mapping)) { + folio_unlock(folio); + folio_put(folio); + goto repeat; + } if (sgp == SGP_WRITE) folio_mark_accessed(folio); if (folio_test_uptodate(folio))
Use the very low level filemap_get_entry helper to look up the entry in the xarray, and then: - don't bother locking the folio if only doing a userfault notification - open code locking the page and checking for truncation in a related code block This will allow to eventually remove the FGP_ENTRY flag. Signed-off-by: Christoph Hellwig <hch@lst.de> --- mm/shmem.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-)