Add a read_folio_sync() handler for buffered writes that filesystems
may pass in if they wish to provide a custom handler for synchronously
reading in the contents of a folio.
Signed-off-by: Joanne Koong <joannelkoong@xxxxxxxxx>
---
.../filesystems/iomap/operations.rst | 7 +++++++
fs/iomap/buffered-io.c | 19 ++++++++++++++++---
include/linux/iomap.h | 11 +++++++++++
3 files changed, 34 insertions(+), 3 deletions(-)
diff --git a/Documentation/filesystems/iomap/operations.rst b/Documentation/filesystems/iomap/operations.rst
index 3b628e370d88..9f0e8a46cc8c 100644
--- a/Documentation/filesystems/iomap/operations.rst
+++ b/Documentation/filesystems/iomap/operations.rst
@@ -72,6 +72,9 @@ default behaviors of iomap:
void (*put_folio)(struct inode *inode, loff_t pos, unsigned copied,
struct folio *folio);
bool (*iomap_valid)(struct inode *inode, const struct iomap *iomap);
+ int (*read_folio_sync)(loff_t block_start, struct folio *folio,
+ size_t off, size_t len,
+ const struct iomap *iomap, void *private);
};
iomap calls these functions:
@@ -102,6 +105,10 @@ iomap calls these functions:
<https://lore.kernel.org/all/20221123055812.747923-8-david@xxxxxxxxxxxxx/>`_
to allocate, install, and lock that folio.
+ - ``read_folio_sync``: Called to synchronously read in the range that will
+ be written to. If this function is not provided, iomap will default to
+ submitting a bio read request.
+
For the pagecache, races can happen if writeback doesn't take
``i_rwsem`` or ``invalidate_lock`` and updates mapping information.
Races can also happen if the filesystem allows concurrent writes.
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 882e55a1d75c..7063a1132694 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -581,10 +581,23 @@ iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
pos + len - 1);
}
+static int iomap_read_folio_sync(const struct iomap_iter *iter,
+ loff_t block_start, struct folio *folio, size_t poff,
+ size_t plen)
+{
+ const struct iomap_folio_ops *folio_ops = iter->iomap.folio_ops;
+ const struct iomap *srcmap = iomap_iter_srcmap(iter);
+
+ if (folio_ops && folio_ops->read_folio_sync)
+ return folio_ops->read_folio_sync(block_start, folio, poff,
+ plen, srcmap, iter->private);
+
+ return iomap_bio_read_folio_sync(block_start, folio, poff, plen, srcmap);
+}
+
static int __iomap_write_begin(const struct iomap_iter *iter, size_t len,
struct folio *folio)
{
- const struct iomap *srcmap = iomap_iter_srcmap(iter);
struct iomap_folio_state *ifs;
loff_t pos = iter->pos;
loff_t block_size = i_blocksize(iter->inode);
@@ -633,8 +646,8 @@ static int __iomap_write_begin(const struct iomap_iter *iter, size_t len,
if (iter->flags & IOMAP_NOWAIT)
return -EAGAIN;
- status = iomap_bio_read_folio_sync(block_start, folio,
- poff, plen, srcmap);
+ status = iomap_read_folio_sync(iter, block_start, folio,
+ poff, plen);
if (status)
return status;
}
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 522644d62f30..51cf3e863caf 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -174,6 +174,17 @@ struct iomap_folio_ops {
* locked by the iomap code.
*/
bool (*iomap_valid)(struct inode *inode, const struct iomap *iomap);
+
+ /*
+ * Optional if the filesystem wishes to provide a custom handler for
+ * reading in the contents of a folio, otherwise iomap will default to
+ * submitting a bio read request.
+ *
+ * The read must be done synchronously.
+ */
+ int (*read_folio_sync)(loff_t block_start, struct folio *folio,
+ size_t off, size_t len, const struct iomap *iomap,
+ void *private);
};
/*
--
2.47.1
