[PATCH 16/20] xfs: add file_{get,put}_folio

Christoph Hellwig
2024-01-29T14:36:04Z

From: "Darrick J. Wong" <djwong@kernel.org>

Add helper similar to file_{get,set}_page, but which deal with folios
and don't allocate new folio unless explicitly asked to, which map
to shmem_get_folio instead of calling into the aops.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kent Overstreet <kent.overstreet@linux.dev>
---
fs/xfs/scrub/trace.h | 2 ++
fs/xfs/scrub/xfile.c | 74 ++++++++++++++++++++++++++++++++++++++++++++
fs/xfs/scrub/xfile.h | 7 +++++
3 files changed, 83 insertions(+)

diff --git a/fs/xfs/scrub/trace.h b/fs/xfs/scrub/trace.h
index 0327cab606b070..c61fa7a95ef522 100644
--- a/fs/xfs/scrub/trace.h
+++ b/fs/xfs/scrub/trace.h
@@ -908,6 +908,8 @@ DEFINE_XFILE_EVENT(xfile_store);
DEFINE_XFILE_EVENT(xfile_seek_data);
DEFINE_XFILE_EVENT(xfile_get_page);
DEFINE_XFILE_EVENT(xfile_put_page);
+DEFINE_XFILE_EVENT(xfile_get_folio);
+DEFINE_XFILE_EVENT(xfile_put_folio);

TRACE_EVENT(xfarray_create,
TP_PROTO(struct xfarray *xfa, unsigned long long required_capacity),
diff --git a/fs/xfs/scrub/xfile.c b/fs/xfs/scrub/xfile.c
index c524fe9980fea2..2d59407909de35 100644
--- a/fs/xfs/scrub/xfile.c
+++ b/fs/xfs/scrub/xfile.c
@@ -340,3 +340,77 @@ xfile_put_page(
return -EIO;
return 0;
}
+
+/*
+ * Grab the (locked) folio for a memory object. The object cannot span a folio
+ * boundary. Returns the locked folio if successful, NULL if there was no
+ * folio or it didn't cover the range requested, or an ERR_PTR on failure.
+ */
+struct folio *
+xfile_get_folio(
+ struct xfile *xf,
+ loff_t pos,
+ size_t len,
+ unsigned int flags)
+{
+ struct inode *inode = file_inode(xf->file);
+ struct folio *folio = NULL;
+ unsigned int pflags;
+ int error;
+
+ if (inode->i_sb->s_maxbytes - pos < len)
+ return ERR_PTR(-ENOMEM);
+
+ trace_xfile_get_folio(xf, pos, len);
+
+ /*
+ * Increase the file size first so that shmem_get_folio(..., SGP_CACHE),
+ * actually allocates a folio instead of erroring out.
+ */
+ if ((flags & XFILE_ALLOC) && pos + len > i_size_read(inode))
+ i_size_write(inode, pos + len);
+
+ pflags = memalloc_nofs_save();
+ error = shmem_get_folio(inode, pos >> PAGE_SHIFT, &folio,
+ (flags & XFILE_ALLOC) ? SGP_CACHE : SGP_READ);
+ memalloc_nofs_restore(pflags);
+ if (error)
+ return ERR_PTR(error);
+
+ if (!folio)
+ return NULL;
+
+ if (len > folio_size(folio) - offset_in_folio(folio, pos)) {
+ folio_unlock(folio);
+ folio_put(folio);
+ return NULL;
+ }
+
+ if (filemap_check_wb_err(inode->i_mapping, 0)) {
+ folio_unlock(folio);
+ folio_put(folio);
+ return ERR_PTR(-EIO);
+ }
+
+ /*
+ * Mark the folio dirty so that it won't be reclaimed once we drop the
+ * (potentially last) reference in xfile_put_folio.
+ */
+ if (flags & XFILE_ALLOC)
+ folio_set_dirty(folio);
+ return folio;
+}
+
+/*
+ * Release the (locked) folio for a memory object.
+ */
+void
+xfile_put_folio(
+ struct xfile *xf,
+ struct folio *folio)
+{
+ trace_xfile_put_folio(xf, folio_pos(folio), folio_size(folio));
+
+ folio_unlock(folio);
+ folio_put(folio);
+}
diff --git a/fs/xfs/scrub/xfile.h b/fs/xfs/scrub/xfile.h
index 465b10f492b66d..afb75e9fbaf265 100644
--- a/fs/xfs/scrub/xfile.h
+++ b/fs/xfs/scrub/xfile.h
@@ -39,4 +39,11 @@ int xfile_get_page(struct xfile *xf, loff_t offset, unsigned int len,
struct xfile_page *xbuf);
int xfile_put_page(struct xfile *xf, struct xfile_page *xbuf);

+#define XFILE_MAX_FOLIO_SIZE (PAGE_SIZE << MAX_PAGECACHE_ORDER)
+
+#define XFILE_ALLOC (1 << 0) /* allocate folio if not present */
+struct folio *xfile_get_folio(struct xfile *xf, loff_t offset, size_t len,
+ unsigned int flags);
+void xfile_put_folio(struct xfile *xf, struct folio *folio);
+
#endif /* __XFS_SCRUB_XFILE_H__ */
--
2.39.2