[PATCH v5 00/25] export/fuse: Use coroutines and multi-threading

[Hanna Czenczek <hreitz@redhat.com>]

Hi,

This series:
- Fixes some bugs/minor inconveniences,
- Removes libfuse from the request processing path,
- Make the FUSE export use coroutines for request handling,

More detail on the v1 cover letter:
https://lists.nongnu.org/archive/html/qemu-block/2025-03/msg00359.html

v2 cover letter:
https://lists.nongnu.org/archive/html/qemu-block/2025-06/msg00040.html

v3 cover letter:
https://lists.nongnu.org/archive/html/qemu-block/2025-07/msg00005.html

v4 cover letter:
https://lists.nongnu.org/archive/html/qemu-block/2026-02/msg00324.html


v4 fixes the problems Kevin has pointed out on list:
- Fix fuse-allow-other test by making the export writable,
- Drop outdated comment,
- Add comment explaining why bufptr should be explicitly set to NULL in
  the empty-read branch of fuse_read().

And the TSA warnings indicated off-list, by making all FUSE handling
functions (which run in a coroutine) GRAPH_RDLOCK, having
fuse_co_process_request() take the lock.  For this, we need to drop the
permission manipulation functions in the I/O path, but that is easy (new
patch 16).


git-backport-diff from v4:

Key:
[----] : patches are identical
[####] : number of functional differences between upstream/downstream patch
[down] : patch is downstream-only
The flags [FC] indicate (F)unctional and (C)ontextual differences, respectively

001/25:[----] [--] 'fuse: Copy write buffer content before polling'
002/25:[----] [--] 'fuse: Ensure init clean-up even with error_fatal'
003/25:[----] [--] 'fuse: Remove superfluous empty line'
004/25:[----] [--] 'fuse: Explicitly set inode ID to 1'
005/25:[----] [--] 'fuse: Change setup_... to mount_fuse_export()'
006/25:[----] [--] 'fuse: Destroy session on mount_fuse_export() fail'
007/25:[0012] [FC] 'fuse: Fix mount options'
008/25:[----] [--] 'fuse: Set direct_io and parallel_direct_writes'
009/25:[----] [--] 'fuse: Introduce fuse_{at,de}tach_handlers()'
010/25:[----] [--] 'fuse: Introduce fuse_{inc,dec}_in_flight()'
011/25:[----] [--] 'fuse: Add halted flag'
012/25:[----] [--] 'fuse: fuse_{read,write}: Rename length to blk_len'
013/25:[----] [--] 'iotests/308: Use conv=notrunc to test growability'
014/25:[----] [--] 'fuse: Explicitly handle non-grow post-EOF accesses'
015/25:[----] [--] 'block: Move qemu_fcntl_addfl() into osdep.c'
016/25:[down] 'fuse: Drop permission changes in fuse_do_truncate'
017/25:[0003] [FC] 'fuse: Manually process requests (without libfuse)'
018/25:[----] [-C] 'fuse: Reduce max read size'
019/25:[0034] [FC] 'fuse: Process requests in coroutines'
020/25:[----] [--] 'block/export: Add multi-threading interface'
021/25:[----] [--] 'iotests/307: Test multi-thread export interface'
022/25:[----] [--] 'fuse: Make shared export state atomic'
023/25:[----] [--] 'fuse: Implement multi-threading'
024/25:[----] [--] 'qapi/block-export: Document FUSE's multi-threading'
025/25:[----] [--] 'iotests/308: Add multi-threading sanity test'


Hanna Czenczek (25):
  fuse: Copy write buffer content before polling
  fuse: Ensure init clean-up even with error_fatal
  fuse: Remove superfluous empty line
  fuse: Explicitly set inode ID to 1
  fuse: Change setup_... to mount_fuse_export()
  fuse: Destroy session on mount_fuse_export() fail
  fuse: Fix mount options
  fuse: Set direct_io and parallel_direct_writes
  fuse: Introduce fuse_{at,de}tach_handlers()
  fuse: Introduce fuse_{inc,dec}_in_flight()
  fuse: Add halted flag
  fuse: fuse_{read,write}: Rename length to blk_len
  iotests/308: Use conv=notrunc to test growability
  fuse: Explicitly handle non-grow post-EOF accesses
  block: Move qemu_fcntl_addfl() into osdep.c
  fuse: Drop permission changes in fuse_do_truncate
  fuse: Manually process requests (without libfuse)
  fuse: Reduce max read size
  fuse: Process requests in coroutines
  block/export: Add multi-threading interface
  iotests/307: Test multi-thread export interface
  fuse: Make shared export state atomic
  fuse: Implement multi-threading
  qapi/block-export: Document FUSE's multi-threading
  iotests/308: Add multi-threading sanity test

 qapi/block-export.json                        |   41 +-
 include/block/export.h                        |   12 +-
 include/qemu/osdep.h                          |    1 +
 block/export/export.c                         |   48 +-
 block/export/fuse.c                           | 1311 +++++++++++++----
 block/export/vduse-blk.c                      |    7 +
 block/export/vhost-user-blk-server.c          |    8 +
 block/file-posix.c                            |   17 +-
 nbd/server.c                                  |    6 +
 util/osdep.c                                  |   18 +
 tests/qemu-iotests/307                        |   47 +
 tests/qemu-iotests/307.out                    |   18 +
 tests/qemu-iotests/308                        |   95 +-
 tests/qemu-iotests/308.out                    |   71 +-
 tests/qemu-iotests/tests/fuse-allow-other     |    3 +-
 tests/qemu-iotests/tests/fuse-allow-other.out |    9 +-
 16 files changed, 1369 insertions(+), 343 deletions(-)

-- 
2.53.0