[PATCH 06/15] ubifs: Convert ubifs_vm_page_mkwrite() to use a folio

Matthew Wilcox (Oracle)
2024-01-20T23:08:49Z

Replace six implicit calls to compound_head() with one.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
Documentation/mm/page_cache.rst | 10 +++++++++
fs/ubifs/file.c | 36 ++++++++++++++++-----------------
2 files changed, 28 insertions(+), 18 deletions(-)

diff --git a/Documentation/mm/page_cache.rst b/Documentation/mm/page_cache.rst
index 75eba7c431b2..138d61f869df 100644
--- a/Documentation/mm/page_cache.rst
+++ b/Documentation/mm/page_cache.rst
@@ -3,3 +3,13 @@
==========
Page Cache
==========
+
+The page cache is the primary way that the user and the rest of the kernel
+interact with filesystems. It can be bypassed (e.g. with O_DIRECT),
+but normal reads, writes and mmaps go through the page cache.
+
+Folios
+======
+
+The folio is the unit of memory management within the page cache.
+Operations
diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index e755d0a11146..9dfedd91b576 100644
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -1519,14 +1519,14 @@ static bool ubifs_release_folio(struct folio *folio, gfp_t unused_gfp_flags)
*/
static vm_fault_t ubifs_vm_page_mkwrite(struct vm_fault *vmf)
{
- struct page *page = vmf->page;
+ struct folio *folio = page_folio(vmf->page);
struct inode *inode = file_inode(vmf->vma->vm_file);
struct ubifs_info *c = inode->i_sb->s_fs_info;
struct timespec64 now = current_time(inode);
struct ubifs_budget_req req = { .new_page = 1 };
int err, update_time;

- dbg_gen("ino %lu, pg %lu, i_size %lld", inode->i_ino, page->index,
+ dbg_gen("ino %lu, pg %lu, i_size %lld", inode->i_ino, folio->index,
i_size_read(inode));
ubifs_assert(c, !c->ro_media && !c->ro_mount);

@@ -1534,17 +1534,17 @@ static vm_fault_t ubifs_vm_page_mkwrite(struct vm_fault *vmf)
return VM_FAULT_SIGBUS; /* -EROFS */

/*
- * We have not locked @page so far so we may budget for changing the
- * page. Note, we cannot do this after we locked the page, because
+ * We have not locked @folio so far so we may budget for changing the
+ * folio. Note, we cannot do this after we locked the folio, because
* budgeting may cause write-back which would cause deadlock.
*
- * At the moment we do not know whether the page is dirty or not, so we
- * assume that it is not and budget for a new page. We could look at
+ * At the moment we do not know whether the folio is dirty or not, so we
+ * assume that it is not and budget for a new folio. We could look at
* the @PG_private flag and figure this out, but we may race with write
- * back and the page state may change by the time we lock it, so this
+ * back and the folio state may change by the time we lock it, so this
* would need additional care. We do not bother with this at the
* moment, although it might be good idea to do. Instead, we allocate
- * budget for a new page and amend it later on if the page was in fact
+ * budget for a new folio and amend it later on if the folio was in fact
* dirty.
*
* The budgeting-related logic of this function is similar to what we
@@ -1567,21 +1567,21 @@ static vm_fault_t ubifs_vm_page_mkwrite(struct vm_fault *vmf)
return VM_FAULT_SIGBUS;
}

- lock_page(page);
- if (unlikely(page->mapping != inode->i_mapping ||
- page_offset(page) > i_size_read(inode))) {
- /* Page got truncated out from underneath us */
+ folio_lock(folio);
+ if (unlikely(folio->mapping != inode->i_mapping ||
+ folio_pos(folio) >= i_size_read(inode))) {
+ /* Folio got truncated out from underneath us */
goto sigbus;
}

- if (PagePrivate(page))
+ if (folio->private)
release_new_page_budget(c);
else {
- if (!PageChecked(page))
+ if (!folio_test_checked(folio))
ubifs_convert_page_budget(c);
- attach_page_private(page, (void *)1);
+ folio_attach_private(folio, (void *)1);
atomic_long_inc(&c->dirty_pg_cnt);
- __set_page_dirty_nobuffers(page);
+ filemap_dirty_folio(folio->mapping, folio);
}

if (update_time) {
@@ -1597,11 +1597,11 @@ static vm_fault_t ubifs_vm_page_mkwrite(struct vm_fault *vmf)
ubifs_release_dirty_inode_budget(c, ui);
}

- wait_for_stable_page(page);
+ folio_wait_stable(folio);
return VM_FAULT_LOCKED;

sigbus:
- unlock_page(page);
+ folio_unlock(folio);
ubifs_release_budget(c, &req);
return VM_FAULT_SIGBUS;
}
--
2.43.0