[PATCH v2 1/7] iomap: Increase iomap_dio_zero() size limit

John Garry
2024-12-10T12:58:27Z

Currently iomap_dio_zero() is limited to using a single bio to write up to
64K.

To support atomic writes larger than the FS block size, it may be required
to pre-zero some extents larger than 64K.

To increase the limit, fill each bio up in a loop.

Signed-off-by: John Garry <john.g.garry@oracle.com>
---
fs/iomap/direct-io.c | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index b521eb15759e..23fdad16e6a8 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -240,27 +240,35 @@ void iomap_dio_bio_end_io(struct bio *bio)
EXPORT_SYMBOL_GPL(iomap_dio_bio_end_io);

static int iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,
- loff_t pos, unsigned len)
+ const loff_t pos, const unsigned len)
{
struct inode *inode = file_inode(dio->iocb->ki_filp);
+ unsigned int remaining = len;
+ unsigned int nr_vecs;
struct bio *bio;
+ int i;

if (!len)
return 0;
- /*
- * Max block size supported is 64k
- */
- if (WARN_ON_ONCE(len > IOMAP_ZERO_PAGE_SIZE))
+
+ nr_vecs = DIV_ROUND_UP(len, IOMAP_ZERO_PAGE_SIZE);
+ if (WARN_ON_ONCE(nr_vecs > BIO_MAX_VECS))
return -EINVAL;

- bio = iomap_dio_alloc_bio(iter, dio, 1, REQ_OP_WRITE | REQ_SYNC | REQ_IDLE);
+ bio = iomap_dio_alloc_bio(iter, dio, nr_vecs,
+ REQ_OP_WRITE | REQ_SYNC | REQ_IDLE);
fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits,
GFP_KERNEL);
bio->bi_iter.bi_sector = iomap_sector(&iter->iomap, pos);
bio->bi_private = dio;
bio->bi_end_io = iomap_dio_bio_end_io;

- __bio_add_page(bio, zero_page, len, 0);
+ for (i = 0; i < nr_vecs; i++) {
+ __bio_add_page(bio, zero_page,
+ min(remaining, IOMAP_ZERO_PAGE_SIZE), 0);
+ remaining -= IOMAP_ZERO_PAGE_SIZE;
+ }
+
iomap_dio_submit_bio(iter, dio, bio, pos);
return 0;
}
--
2.31.1