iomap/gfs2: Get page in page_prepare handler

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>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 0c041459677bf8affce7d3f32ac598ab4971a361..41349e09558b810a273c4757531e991c4ceb6af4 100644 (file)
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -956,15 +956,25 @@ hole_found:
        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 de4a8e5f721a54d32305109536108c125345516d..418519dea2ce1e438bb977026853c1bab15a0fba 100644 (file)
--- 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 188d14e786a41c87701205e1aea5787e888a721d..d50501781856811eb9f054ad52fc5a03dc63a88c 100644 (file)
--- 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);