mm: introduce memdesc_flags_t

Patch series "Add and use memdesc_flags_t".

At some point struct page will be separated from struct slab and struct
folio.  This is a step towards that by introducing a type for the 'flags'
word of all three structures.  This gives us a certain amount of type
safety by establishing that some of these unsigned longs are different
from other unsigned longs in that they contain things like node ID,
section number and zone number in the upper bits.  That lets us have
functions that can be easily called by anyone who has a slab, folio or
page (but not easily by anyone else) to get the node or zone.

There's going to be some unusual merge problems with this as some odd bits
of the kernel decide they want to print out the flags value or something
similar by writing page->flags and now they'll need to write page->flags.f
instead.  That's most of the churn here.  Maybe we should be removing
these things from the debug output?


This patch (of 11):

Wrap the unsigned long flags in a typedef.  In upcoming patches, this will
provide a strong hint that you can't just pass a random unsigned long to
functions which take this as an argument.

[willy@infradead.org: s/flags/flags.f/ in several architectures]
  Link: https://lkml.kernel.org/r/aKMgPRLD-WnkPxYm@casper.infradead.org
[nicola.vetrini@gmail.com: mips: fix compilation error]
  Link: https://lore.kernel.org/lkml/CA+G9fYvkpmqGr6wjBNHY=dRp71PLCoi2341JxOudi60yqaeUdg@mail.gmail.com/
  Link: https://lkml.kernel.org/r/20250825214245.1838158-1-nicola.vetrini@gmail.com
Link: https://lkml.kernel.org/r/20250805172307.1302730-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20250805172307.1302730-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Zi Yan <ziy@nvidia.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

6 files changed, 10 insertions, 10 deletions

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index e80cd8f2c049..8a89f0aa1d4d 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -935,7 +935,7 @@ static int fuse_check_folio(struct folio *folio)
 {
 	if (folio_mapped(folio) ||
 	    folio->mapping != NULL ||
-	    (folio->flags & PAGE_FLAGS_CHECK_AT_PREP &
+	    (folio->flags.f & PAGE_FLAGS_CHECK_AT_PREP &
 	     ~(1 << PG_locked |
 	       1 << PG_referenced |
 	       1 << PG_lru |
diff --git a/fs/gfs2/glops.c b/fs/gfs2/glops.c
index fe0faad4892f..0c0a80b3baca 100644
--- a/fs/gfs2/glops.c
+++ b/fs/gfs2/glops.c
@@ -40,7 +40,7 @@ static void gfs2_ail_error(struct gfs2_glock *gl, const struct buffer_head *bh)
 	       "AIL buffer %p: blocknr %llu state 0x%08lx mapping %p page "
 	       "state 0x%lx\n",
 	       bh, (unsigned long long)bh->b_blocknr, bh->b_state,
-	       bh->b_folio->mapping, bh->b_folio->flags);
+	       bh->b_folio->mapping, bh->b_folio->flags.f);
 	fs_err(sdp, "AIL glock %u:%llu mapping %p\n",
 	       gl->gl_name.ln_type, gl->gl_name.ln_number,
 	       gfs2_glock2aspace(gl));
diff --git a/fs/jffs2/file.c b/fs/jffs2/file.c
index dd3dff95cb24..b697f3c259ef 100644
--- a/fs/jffs2/file.c
+++ b/fs/jffs2/file.c
@@ -230,7 +230,7 @@ static int jffs2_write_begin(const struct kiocb *iocb,
 			goto release_sem;
 		}
 	}
-	jffs2_dbg(1, "end write_begin(). folio->flags %lx\n", folio->flags);
+	jffs2_dbg(1, "end write_begin(). folio->flags %lx\n", folio->flags.f);
 
 release_sem:
 	mutex_unlock(&c->alloc_sem);
@@ -259,7 +259,7 @@ static int jffs2_write_end(const struct kiocb *iocb,
 
 	jffs2_dbg(1, "%s(): ino #%lu, page at 0x%llx, range %d-%d, flags %lx\n",
 		  __func__, inode->i_ino, folio_pos(folio),
-		  start, end, folio->flags);
+		  start, end, folio->flags.f);
 
 	/* We need to avoid deadlock with page_cache_read() in
 	   jffs2_garbage_collect_pass(). So the folio must be
diff --git a/fs/nilfs2/page.c b/fs/nilfs2/page.c
index 806b056d2260..56c4da417b6a 100644
--- a/fs/nilfs2/page.c
+++ b/fs/nilfs2/page.c
@@ -167,7 +167,7 @@ void nilfs_folio_bug(struct folio *folio)
 	printk(KERN_CRIT "NILFS_FOLIO_BUG(%p): cnt=%d index#=%llu flags=0x%lx "
 	       "mapping=%p ino=%lu\n",
 	       folio, folio_ref_count(folio),
-	       (unsigned long long)folio->index, folio->flags, m, ino);
+	       (unsigned long long)folio->index, folio->flags.f, m, ino);
 
 	head = folio_buffers(folio);
 	if (head) {
diff --git a/fs/proc/page.c b/fs/proc/page.c
index ba3568e97fd1..771e0b6bc630 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -163,7 +163,7 @@ u64 stable_page_flags(const struct page *page)
 	snapshot_page(&ps, page);
 	folio = &ps.folio_snapshot;
 
-	k = folio->flags;
+	k = folio->flags.f;
 	mapping = (unsigned long)folio->mapping;
 	is_anon = mapping & FOLIO_MAPPING_ANON;
 
@@ -238,7 +238,7 @@ u64 stable_page_flags(const struct page *page)
 	if (u & (1 << KPF_HUGE))
 		u |= kpf_copy_bit(k, KPF_HWPOISON,	PG_hwpoison);
 	else
-		u |= kpf_copy_bit(ps.page_snapshot.flags, KPF_HWPOISON, PG_hwpoison);
+		u |= kpf_copy_bit(ps.page_snapshot.flags.f, KPF_HWPOISON, PG_hwpoison);
 #endif
 
 	u |= kpf_copy_bit(k, KPF_RESERVED,	PG_reserved);
diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index e75a6cec67be..ca41ce8208c4 100644
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -107,7 +107,7 @@ static int do_readpage(struct folio *folio)
 	size_t offset = 0;
 
 	dbg_gen("ino %lu, pg %lu, i_size %lld, flags %#lx",
-		inode->i_ino, folio->index, i_size, folio->flags);
+		inode->i_ino, folio->index, i_size, folio->flags.f);
 	ubifs_assert(c, !folio_test_checked(folio));
 	ubifs_assert(c, !folio->private);
 
@@ -600,7 +600,7 @@ static int populate_page(struct ubifs_info *c, struct folio *folio,
 	pgoff_t end_index;
 
 	dbg_gen("ino %lu, pg %lu, i_size %lld, flags %#lx",
-		inode->i_ino, folio->index, i_size, folio->flags);
+		inode->i_ino, folio->index, i_size, folio->flags.f);
 
 	end_index = (i_size - 1) >> PAGE_SHIFT;
 	if (!i_size || folio->index > end_index) {
@@ -988,7 +988,7 @@ static int ubifs_writepage(struct folio *folio, struct writeback_control *wbc)
 	int err, len = folio_size(folio);
 
 	dbg_gen("ino %lu, pg %lu, pg flags %#lx",
-		inode->i_ino, folio->index, folio->flags);
+		inode->i_ino, folio->index, folio->flags.f);
 	ubifs_assert(c, folio->private != NULL);
 
 	/* Is the folio fully outside @i_size? (truncate in progress) */