mm: return an ERR_PTR from __filemap_get_folio
Instead of returning NULL for all errors, distinguish between:
- no entry found and not asked to allocated (-ENOENT)
- failed to allocate memory (-ENOMEM)
- would block (-EAGAIN)
so that callers don't have to guess the error based on the passed in
flags.
Also pass through the error through the direct callers: filemap_get_folio,
filemap_lock_folio filemap_grab_folio and filemap_get_incore_folio.
[hch@lst.de: fix null-pointer deref]
Link: https://lkml.kernel.org/r/20230310070023.GA13563@lst.de
Link: https://lkml.kernel.org/r/20230310043137.GA1624890@u2004
Link: https://lkml.kernel.org/r/20230307143410.28031-8-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Ryusuke Konishi <konishi.ryusuke@gmail.com> [nilfs2]
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
diff --git a/mm/shmem.c b/mm/shmem.c
index 93cb398..fa6e38f 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -605,7 +605,7 @@ static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
index = (inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT;
folio = filemap_get_folio(inode->i_mapping, index);
- if (!folio)
+ if (IS_ERR(folio))
goto drop;
/* No huge page at the end of the file: nothing to split */
@@ -3214,7 +3214,7 @@ static const char *shmem_get_link(struct dentry *dentry,
if (!dentry) {
folio = filemap_get_folio(inode->i_mapping, 0);
- if (!folio)
+ if (IS_ERR(folio))
return ERR_PTR(-ECHILD);
if (PageHWPoison(folio_page(folio, 0)) ||
!folio_test_uptodate(folio)) {
