Re: [PATCH v3 1/2] nilfs2: add iomap operations for direct I/O

On Thu, Aug 13, 2026 at 7:12 AM Viacheslav Dubeyko wrote:
>
> The patch adds iomap.h with declaration of iomaps
> operations and iomap.c with implementation of
> nilfs_iomap_begin(). This method is based on calling
> the nilfs_bmap_lookup_contig() method. It resolves
> the file's block-mapping to find the sequence of
> physically-contiguous blocks starting at starting
> block. Offsets at or beyond i_size are reported
> as a hole. For offsets within i_size, the requested
> length is first clamped to the block-aligned end of the file.
> Both the hole and mapped cases then report iomap->offset
> aligned to the containing block (blkoff << i_blkbits)
> rather than the raw request offset.
>
> Signed-off-by: Viacheslav Dubeyko <[email protected]>
> Co-developed-by: Linmao Li <[email protected]>
> Signed-off-by: Linmao Li <[email protected]>
> cc: Christoph Hellwig <[email protected]>
> cc: Ryusuke Konishi <[email protected]>
> cc: [email protected]
> cc: [email protected]
> ---

Acked-by: Ryusuke Konishi <[email protected]>

Thanks,
Ryusuke Konishi

>  fs/nilfs2/Makefile |  2 +-
>  fs/nilfs2/iomap.c  | 72 ++++++++++++++++++++++++++++++++++++++++++++++
>  fs/nilfs2/iomap.h  | 13 +++++++++
>  3 files changed, 86 insertions(+), 1 deletion(-)
>  create mode 100644 fs/nilfs2/iomap.c
>  create mode 100644 fs/nilfs2/iomap.h
>
> diff --git a/fs/nilfs2/Makefile b/fs/nilfs2/Makefile
> index 43b60b8a4d07..516e6b85a03c 100644
> --- a/fs/nilfs2/Makefile
> +++ b/fs/nilfs2/Makefile
> @@ -3,4 +3,4 @@ obj-$(CONFIG_NILFS2_FS) += nilfs2.o
>  nilfs2-y := inode.o file.o dir.o super.o namei.o page.o mdt.o \
>         btnode.o bmap.o btree.o direct.o dat.o recovery.o \
>         the_nilfs.o segbuf.o segment.o cpfile.o sufile.o \
> -       ifile.o alloc.o gcinode.o ioctl.o sysfs.o
> +       ifile.o alloc.o gcinode.o ioctl.o sysfs.o iomap.o
> diff --git a/fs/nilfs2/iomap.c b/fs/nilfs2/iomap.c
> new file mode 100644
> index 000000000000..e130ed63abd9
> --- /dev/null
> +++ b/fs/nilfs2/iomap.c
> @@ -0,0 +1,72 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * NILFS iomap support implementation.
> + *
> + * Written by Viacheslav Dubeyko.
> + */
> +
> +#include <linux/iomap.h>
> +#include <linux/pagemap.h>
> +#include "nilfs.h"
> +#include "mdt.h"
> +#include "iomap.h"
> +
> +static int nilfs_iomap_begin(struct inode *inode, loff_t offset,
> +                            loff_t length, unsigned int flags,
> +                            struct iomap *iomap, struct iomap *srcmap)
> +{
> +       struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
> +       struct nilfs_inode_info *ii = NILFS_I(inode);
> +       sector_t blkoff = offset >> inode->i_blkbits;
> +       loff_t iomap_offset = (loff_t)blkoff << inode->i_blkbits;
> +       unsigned int maxblocks;
> +       __u64 blknum = 0;
> +       int ret;
> +
> +       /* Completely beyond EOF. Treat as hole */
> +       if (i_size_read(inode) <= offset) {
> +               iomap->type = IOMAP_HOLE;
> +               iomap->addr = IOMAP_NULL_ADDR;
> +               iomap->offset = offset;
> +               iomap->length = length;
> +               return 0;
> +       }
> +
> +       /* Clamp length if the requested range goes beyond i_size */
> +       if (offset + length > i_size_read(inode)) {
> +               loff_t i_size = i_size_read(inode);
> +               unsigned int blocksize = i_blocksize(inode);
> +
> +               length = round_up(i_size, blocksize) - offset;
> +       }
> +
> +       maxblocks = min_t(loff_t, length >> inode->i_blkbits, INT_MAX);
> +       if (maxblocks == 0)
> +               maxblocks = 1;
> +
> +       down_read(&NILFS_MDT(nilfs->ns_dat)->mi_sem);
> +       ret = nilfs_bmap_lookup_contig(ii->i_bmap, blkoff, &blknum, maxblocks);
> +       up_read(&NILFS_MDT(nilfs->ns_dat)->mi_sem);
> +
> +       if (ret == -ENOENT) {
> +               iomap->type = IOMAP_HOLE;
> +               iomap->addr = IOMAP_NULL_ADDR;
> +               iomap->offset = iomap_offset;
> +               iomap->length = i_blocksize(inode);
> +               return 0;
> +       } else if (ret < 0)
> +               return ret;
> +
> +       iomap->bdev = inode->i_sb->s_bdev;
> +       iomap->offset = iomap_offset;
> +       iomap->length = (loff_t)ret << inode->i_blkbits;
> +       iomap->addr = (loff_t)blknum << inode->i_blkbits;
> +       iomap->type = IOMAP_MAPPED;
> +       iomap->flags = IOMAP_F_MERGED;
> +
> +       return 0;
> +}
> +
> +const struct iomap_ops nilfs_iomap_ops = {
> +       .iomap_begin = nilfs_iomap_begin,
> +};
> diff --git a/fs/nilfs2/iomap.h b/fs/nilfs2/iomap.h
> new file mode 100644
> index 000000000000..adef3e22346d
> --- /dev/null
> +++ b/fs/nilfs2/iomap.h
> @@ -0,0 +1,13 @@
> +/* SPDX-License-Identifier: GPL-2.0+ */
> +/*
> + * NILFS iomap support declarations.
> + *
> + * Written by Viacheslav Dubeyko.
> + */
> +
> +#ifndef _NILFS_IOMAP_H
> +#define _NILFS_IOMAP_H
> +
> +extern const struct iomap_ops nilfs_iomap_ops;
> +
> +#endif /* _NILFS_IOMAP_H */
> --
> 2.43.0
>