[PATCH v5 5/9] iomap/gfs2: Get page in page_prepare handler

Andreas Gruenbacher
2022-12-31T15:11:14Z

Change the iomap ->page_prepare() handler to get and return a locked
folio instead of doing that in iomap_write_begin(). This allows to
recover from out-of-memory situations in ->page_prepare(), which
eliminates the corresponding error handling code in iomap_write_begin().
The ->put_folio() handler now also isn't called with NULL as the folio
value anymore.

Filesystems are expected to use the iomap_get_folio() helper for getting
locked folios in their ->page_prepare() handlers.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
fs/gfs2/bmap.c | 21 +++++++++++++--------
fs/iomap/buffered-io.c | 17 ++++++-----------
include/linux/iomap.h | 9 +++++----
3 files changed, 24 insertions(+), 23 deletions(-)

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 0c041459677b..41349e09558b 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -956,15 +956,25 @@ static int __gfs2_iomap_get(struct inode *inode, loff_t pos, loff_t length,
goto out;
}

-static int gfs2_iomap_page_prepare(struct inode *inode, loff_t pos,
- unsigned len)
+static struct folio *
+gfs2_iomap_page_prepare(struct iomap_iter *iter, loff_t pos, unsigned len)
{
+ struct inode *inode = iter->inode;
unsigned int blockmask = i_blocksize(inode) - 1;
struct gfs2_sbd *sdp = GFS2_SB(inode);
unsigned int blocks;
+ struct folio *folio;
+ int status;

blocks = ((pos & blockmask) + len + blockmask) >> inode->i_blkbits;
- return gfs2_trans_begin(sdp, RES_DINODE + blocks, 0);
+ status = gfs2_trans_begin(sdp, RES_DINODE + blocks, 0);
+ if (status)
+ return ERR_PTR(status);
+
+ folio = iomap_get_folio(iter, pos);
+ if (IS_ERR(folio))
+ gfs2_trans_end(sdp);
+ return folio;
}

static void gfs2_iomap_put_folio(struct inode *inode, loff_t pos,
@@ -974,11 +984,6 @@ static void gfs2_iomap_put_folio(struct inode *inode, loff_t pos,
struct gfs2_inode *ip = GFS2_I(inode);
struct gfs2_sbd *sdp = GFS2_SB(inode);

- if (!folio) {
- gfs2_trans_end(sdp);
- return;
- }
-
if (!gfs2_is_stuffed(ip))
gfs2_page_add_databufs(ip, &folio->page, offset_in_page(pos),
copied);
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index b84838d2b5d8..7decd8cdc755 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -609,7 +609,7 @@ static void iomap_put_folio(struct iomap_iter *iter, loff_t pos, size_t ret,

if (page_ops && page_ops->put_folio) {
page_ops->put_folio(iter->inode, pos, ret, folio);
- } else if (folio) {
+ } else {
folio_unlock(folio);
folio_put(folio);
}
@@ -642,17 +642,12 @@ static int iomap_write_begin(struct iomap_iter *iter, loff_t pos,
if (!mapping_large_folio_support(iter->inode->i_mapping))
len = min_t(size_t, len, PAGE_SIZE - offset_in_page(pos));

- if (page_ops && page_ops->page_prepare) {
- status = page_ops->page_prepare(iter->inode, pos, len);
- if (status)
- return status;
- }
-
- folio = iomap_get_folio(iter, pos);
- if (IS_ERR(folio)) {
- iomap_put_folio(iter, pos, 0, NULL);
+ if (page_ops && page_ops->page_prepare)
+ folio = page_ops->page_prepare(iter, pos, len);
+ else
+ folio = iomap_get_folio(iter, pos);
+ if (IS_ERR(folio))
return PTR_ERR(folio);
- }

/*
* Now we have a locked folio, before we do anything with it we need to
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index e5732cc5716b..87b5d0f8e578 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -13,6 +13,7 @@
struct address_space;
struct fiemap_extent_info;
struct inode;
+struct iomap_iter;
struct iomap_dio;
struct iomap_writepage_ctx;
struct iov_iter;
@@ -131,12 +132,12 @@ static inline bool iomap_inline_data_valid(const struct iomap *iomap)
* associated with them.
*
* When page_prepare succeeds, put_folio will always be called to do any
- * cleanup work necessary. In that put_folio call, @folio will be NULL if the
- * associated folio could not be obtained. When folio is not NULL, put_folio
- * is responsible for unlocking and putting the folio.
+ * cleanup work necessary. put_folio is responsible for unlocking and putting
+ * @folio.
*/
struct iomap_page_ops {
- int (*page_prepare)(struct inode *inode, loff_t pos, unsigned len);
+ struct folio *(*page_prepare)(struct iomap_iter *iter, loff_t pos,
+ unsigned len);
void (*put_folio)(struct inode *inode, loff_t pos, unsigned copied,
struct folio *folio);

--
2.38.1