[PATCH 0/2] nilfs2: convert O_DIRECT reads to iomap

[Viacheslav Dubeyko <slava@dubeyko.com>]

This series removes NILFS2 using of blockdev_direct_IO() by
converting the O_DIRECT read path to iomap. NILFS2 is
a log-structured, copy-on-write filesystem, which makes it
a poor fit for a full iomap conversion. Newly allocated blocks
are delay-allocated by nilfs_get_block() and only receive a real
disk address when the segment constructor writes them out
as part of a log. The segment constructor walks buffer_head lists
directly and is not integrated with the generic address_space
writeback path. First patch adds a new, read-only nilfs_iomap_ops
wrapping the existing nilfs_bmap_lookup_contig() lookup.
The second patch wires that ops table into O_DIRECT reads via
iomap_dio_rw(), sets FMODE_CAN_ODIRECT explicitly on open, and
removes nilfs_direct_IO() and the .direct_IO callback entirely.
O_DIRECT writes are explicitly downgraded to the ordinary buffered
write path in nilfs_file_write_iter().

Viacheslav Dubeyko (2):
  nilfs2: add iomap operations for direct I/O reads
  nilfs2: switch O_DIRECT reads to iomap

 fs/nilfs2/Kconfig  |  2 +-
 fs/nilfs2/Makefile |  2 +-
 fs/nilfs2/file.c   | 40 ++++++++++++++++++++++++--
 fs/nilfs2/inode.c  | 13 ---------
 fs/nilfs2/iomap.c  | 71 ++++++++++++++++++++++++++++++++++++++++++++++
 fs/nilfs2/iomap.h  | 13 +++++++++
 6 files changed, 123 insertions(+), 18 deletions(-)
 create mode 100644 fs/nilfs2/iomap.c
 create mode 100644 fs/nilfs2/iomap.h

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2.43.0