[PATCH v14 117/138] mm/filemap: Convert filemap_fault to folio

Matthew Wilcox (Oracle)
2021-07-15T05:13:35Z

Instead of converting back-and-forth between the actual page and
the head page, just convert once at the end of the function where we
set the vmf->page. Saves 241 bytes of text, or 15% of the size of
filemap_fault().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
mm/filemap.c | 78 +++++++++++++++++++++++++---------------------------
1 file changed, 38 insertions(+), 40 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 078c318e2f16..b0fe3234a20b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2801,21 +2801,20 @@ loff_t mapping_seek_hole_data(struct address_space *mapping, loff_t start,
#ifdef CONFIG_MMU
#define MMAP_LOTSAMISS (100)
/*
- * lock_page_maybe_drop_mmap - lock the page, possibly dropping the mmap_lock
+ * lock_folio_maybe_drop_mmap - lock the page, possibly dropping the mmap_lock
* @vmf - the vm_fault for this fault.
- * @page - the page to lock.
+ * @folio - the folio to lock.
* @fpin - the pointer to the file we may pin (or is already pinned).
*
- * This works similar to lock_page_or_retry in that it can drop the mmap_lock.
- * It differs in that it actually returns the page locked if it returns 1 and 0
- * if it couldn't lock the page. If we did have to drop the mmap_lock then fpin
- * will point to the pinned file and needs to be fput()'ed at a later point.
+ * This works similar to lock_folio_or_retry in that it can drop the
+ * mmap_lock. It differs in that it actually returns the folio locked
+ * if it returns 1 and 0 if it couldn't lock the folio. If we did have
+ * to drop the mmap_lock then fpin will point to the pinned file and
+ * needs to be fput()'ed at a later point.
*/
-static int lock_page_maybe_drop_mmap(struct vm_fault *vmf, struct page *page,
+static int lock_folio_maybe_drop_mmap(struct vm_fault *vmf, struct folio *folio,
struct file **fpin)
{
- struct folio *folio = page_folio(page);
-
if (folio_trylock(folio))
return 1;

@@ -2904,7 +2903,7 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
* was pinned if we have to drop the mmap_lock in order to do IO.
*/
static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
- struct page *page)
+ struct folio *folio)
{
struct file *file = vmf->vma->vm_file;
struct file_ra_state *ra = &file->f_ra;
@@ -2919,10 +2918,10 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
mmap_miss = READ_ONCE(ra->mmap_miss);
if (mmap_miss)
WRITE_ONCE(ra->mmap_miss, --mmap_miss);
- if (PageReadahead(page)) {
+ if (folio_test_readahead(folio)) {
fpin = maybe_unlock_mmap_for_io(vmf, fpin);
page_cache_async_readahead(mapping, ra, file,
- page, offset, ra->ra_pages);
+ &folio->page, offset, ra->ra_pages);
}
return fpin;
}
@@ -2941,7 +2940,7 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
* vma->vm_mm->mmap_lock must be held on entry.
*
* If our return value has VM_FAULT_RETRY set, it's because the mmap_lock
- * may be dropped before doing I/O or by lock_page_maybe_drop_mmap().
+ * may be dropped before doing I/O or by lock_folio_maybe_drop_mmap().
*
* If our return value does not have VM_FAULT_RETRY set, the mmap_lock
* has not been released.
@@ -2957,58 +2956,57 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
struct file *fpin = NULL;
struct address_space *mapping = file->f_mapping;
struct inode *inode = mapping->host;
- pgoff_t offset = vmf->pgoff;
- pgoff_t max_off;
- struct page *page;
+ pgoff_t max_idx, index = vmf->pgoff;
+ struct folio *folio;
vm_fault_t ret = 0;

- max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
- if (unlikely(offset >= max_off))
+ max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ if (unlikely(index >= max_idx))
return VM_FAULT_SIGBUS;

/*
* Do we have something in the page cache already?
*/
- page = find_get_page(mapping, offset);
- if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
+ folio = filemap_get_folio(mapping, index);
+ if (likely(folio) && !(vmf->flags & FAULT_FLAG_TRIED)) {
/*
* We found the page, so try async readahead before
* waiting for the lock.
*/
- fpin = do_async_mmap_readahead(vmf, page);
- } else if (!page) {
+ fpin = do_async_mmap_readahead(vmf, folio);
+ } else if (!folio) {
/* No page in the page cache at all */
count_vm_event(PGMAJFAULT);
count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
ret = VM_FAULT_MAJOR;
fpin = do_sync_mmap_readahead(vmf);
retry_find:
- page = pagecache_get_page(mapping, offset,
+ folio = __filemap_get_folio(mapping, index,
FGP_CREAT|FGP_FOR_MMAP,
vmf->gfp_mask);
- if (!page) {
+ if (!folio) {
if (fpin)
goto out_retry;
return VM_FAULT_OOM;
}
}

- if (!lock_page_maybe_drop_mmap(vmf, page, &fpin))
+ if (!lock_folio_maybe_drop_mmap(vmf, folio, &fpin))
goto out_retry;

/* Did it get truncated? */
- if (unlikely(compound_head(page)->mapping != mapping)) {
- unlock_page(page);
- put_page(page);
+ if (unlikely(folio->mapping != mapping)) {
+ folio_unlock(folio);
+ folio_put(folio);
goto retry_find;
}
- VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
+ VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);

/*
* We have a locked page in the page cache, now we need to check
* that it's up-to-date. If not, it is going to be due to an error.
*/
- if (unlikely(!PageUptodate(page)))
+ if (unlikely(!folio_test_uptodate(folio)))
goto page_not_uptodate;

/*
@@ -3017,7 +3015,7 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
* redo the fault.
*/
if (fpin) {
- unlock_page(page);
+ folio_unlock(folio);
goto out_retry;
}

@@ -3025,14 +3023,14 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
* Found the page and have a reference on it.
* We must recheck i_size under page lock.
*/
- max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
- if (unlikely(offset >= max_off)) {
- unlock_page(page);
- put_page(page);
+ max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ if (unlikely(index >= max_idx)) {
+ folio_unlock(folio);
+ folio_put(folio);
return VM_FAULT_SIGBUS;
}

- vmf->page = page;
+ vmf->page = folio_file_page(folio, index);
return ret | VM_FAULT_LOCKED;

page_not_uptodate:
@@ -3043,10 +3041,10 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
* and we need to check for errors.
*/
fpin = maybe_unlock_mmap_for_io(vmf, fpin);
- error = filemap_read_folio(file, mapping, page_folio(page));
+ error = filemap_read_folio(file, mapping, folio);
if (fpin)
goto out_retry;
- put_page(page);
+ folio_put(folio);

if (!error || error == AOP_TRUNCATED_PAGE)
goto retry_find;
@@ -3059,8 +3057,8 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
* re-find the vma and come back and find our hopefully still populated
* page.
*/
- if (page)
- put_page(page);
+ if (folio)
+ folio_put(folio);
if (fpin)
fput(fpin);
return ret | VM_FAULT_RETRY;
--
2.30.2