blkdev_direct_IO() currently uses BIO_MAX_PAGES for maximum IO transfer size.
For more than a decade its value has been fixed to 256. With 4.14+ and commit
225311a4 ("mm: test code to write THP to swap device as a whole") this has
increased to 512. Tests with older FusionIO cards show that the new setting
totally breaks direct IO. The driver advertises max_hw_blocks_kb=1024 and
max_segments=257 and expects the upper layers to cut data correspondingly.
Other propretary drivers might face similar problems. Fix that by respecting
sane values in bdi->io_pages. Patch could qualify for stable.
Signed-off-by: Markus Stockhausen stockhausen@xxxxxxxxxxx
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 2f777f9..6263f75 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -420,15 +420,21 @@ static void blkdev_bio_end_io(struct bio *bio)
static ssize_t
blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
{
+ struct file *file = iocb->ki_filp;
+ struct inode *inode = bdev_file_inode(file);
+ struct block_device *bdev = I_BDEV(inode);
+ struct backing_dev_info *bdi = bdev->bd_bdi;
+ int max_io_pages;
int nr_pages;
- nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES + 1);
+ max_io_pages = min_not_zero(bdi->io_pages, (unsigned long)BIO_MAX_PAGES);
+ nr_pages = iov_iter_npages(iter, max_io_pages + 1);
if (!nr_pages)
return 0;
- if (is_sync_kiocb(iocb) && nr_pages <= BIO_MAX_PAGES)
+ if (is_sync_kiocb(iocb) && nr_pages <= max_io_pages)
return __blkdev_direct_IO_simple(iocb, iter, nr_pages);
- return __blkdev_direct_IO(iocb, iter, min(nr_pages, BIO_MAX_PAGES), BIO_MAX_PAGES);
+ return __blkdev_direct_IO(iocb, iter, min(nr_pages, max_io_pages), max_io_pages);
}
static __init int blkdev_init(void)****************************************************************************
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