Re: [PATCH RFC v5 00/29] io_uring getdents

From: Darrick J. Wong
Date: Fri Aug 25 2023 - 11:11:58 EST

On Fri, Aug 25, 2023 at 09:54:02PM +0800, Hao Xu wrote:
> From: Hao Xu <howeyxu@xxxxxxxxxxx>
>
> This series introduce getdents64 to io_uring, the code logic is similar
> with the snychronized version's. It first try nowait issue, and offload
> it to io-wq threads if the first try fails.

NAK on the entire series until Jens actually writes down what NOWAIT
does, so that we can check that the *existing* nowait code branches
actually behave how he says it should.

https://lore.kernel.org/all/e2d8e5f1-f794-38eb-cecf-ed30c571206b@xxxxxxxxx/

--D

>
> Patch1 and Patch2 are some preparation
> Patch3 supports nowait for xfs getdents code
> Patch4-11 are vfs change, include adding helpers and trylock for locks
> Patch12-29 supports nowait for involved xfs journal stuff
> note, Patch24 and 27 are actually two questions, might be removed later.
> an xfs test may come later.
>
> Tests I've done:
> a liburing test case for functional test:
> https://github.com/HowHsu/liburing/commit/39dc9a8e19c06a8cebf8c2301b85320eb45c061e?diff=unified
>
> xfstests:
> test/generic: 1 fails and 171 not run
> test/xfs: 72 fails and 156 not run
> run the code before without this patchset, same result.
> I'll try to make the environment more right to run more tests here.
>
>
> Tested it with a liburing performance test:
> https://github.com/HowHsu/liburing/blob/getdents/test/getdents2.c
>
> The test is controlled by the below script[2] which runs getdents2.t 100
> times and calulate the avg.
> The result show that io_uring version is about 2.6% faster:
>
> note:
> [1] the number of getdents call/request in io_uring and normal sync version
> are made sure to be same beforehand.
>
> [2] run_getdents.py
>
> ```python3
>
> import subprocess
>
> N = 100
> sum = 0.0
> args = ["/data/home/howeyxu/tmpdir", "sync"]
>
> for i in range(N):
> output = subprocess.check_output(["./liburing/test/getdents2.t"] + args)
> sum += float(output)
>
> average = sum / N
> print("Average of sync:", average)
>
> sum = 0.0
> args = ["/data/home/howeyxu/tmpdir", "iouring"]
>
> for i in range(N):
> output = subprocess.check_output(["./liburing/test/getdents2.t"] + args)
> sum += float(output)
>
> average = sum / N
> print("Average of iouring:", average)
>
> ```
>
> v4->v5:
> - move atime update to the beginning of getdents operation
> - trylock for i_rwsem
> - nowait semantics for involved xfs journal stuff
>
> v3->v4:
> - add Dave's xfs nowait code and fix a deadlock problem, with some code
> style tweak.
> - disable fixed file to avoid a race problem for now
> - add a test program.
>
> v2->v3:
> - removed the kernfs patches
> - add f_pos_lock logic
> - remove the "reduce last EOF getdents try" optimization since
> Dominique reports that doesn't make difference
> - remove the rewind logic, I think the right way is to introduce lseek
> to io_uring not to patch this logic to getdents.
> - add Singed-off-by of Stefan Roesch for patch 1 since checkpatch
> complained that Co-developed-by someone should be accompanied with
> Signed-off-by same person, I can remove them if Stefan thinks that's
> not proper.
>
>
> Dominique Martinet (1):
> fs: split off vfs_getdents function of getdents64 syscall
>
> Hao Xu (28):
> xfs: rename XBF_TRYLOCK to XBF_NOWAIT
> xfs: add NOWAIT semantics for readdir
> vfs: add nowait flag for struct dir_context
> vfs: add a vfs helper for io_uring file pos lock
> vfs: add file_pos_unlock() for io_uring usage
> vfs: add a nowait parameter for touch_atime()
> vfs: add nowait parameter for file_accessed()
> vfs: move file_accessed() to the beginning of iterate_dir()
> vfs: add S_NOWAIT for nowait time update
> vfs: trylock inode->i_rwsem in iterate_dir() to support nowait
> xfs: enforce GFP_NOIO implicitly during nowait time update
> xfs: make xfs_trans_alloc() support nowait semantics
> xfs: support nowait for xfs_log_reserve()
> xfs: don't wait for free space in xlog_grant_head_check() in nowait
> case
> xfs: add nowait parameter for xfs_inode_item_init()
> xfs: make xfs_trans_ijoin() error out -EAGAIN
> xfs: set XBF_NOWAIT for xfs_buf_read_map if necessary
> xfs: support nowait memory allocation in _xfs_buf_alloc()
> xfs: distinguish error type of memory allocation failure for nowait
> case
> xfs: return -EAGAIN when bulk memory allocation fails in nowait case
> xfs: comment page allocation for nowait case in xfs_buf_find_insert()
> xfs: don't print warn info for -EAGAIN error in xfs_buf_get_map()
> xfs: support nowait for xfs_buf_read_map()
> xfs: support nowait for xfs_buf_item_init()
> xfs: return -EAGAIN when nowait meets sync in transaction commit
> xfs: add a comment for xlog_kvmalloc()
> xfs: support nowait semantics for xc_ctx_lock in xlog_cil_commit()
> io_uring: add support for getdents
>
> arch/s390/hypfs/inode.c | 2 +-
> block/fops.c | 2 +-
> fs/btrfs/file.c | 2 +-
> fs/btrfs/inode.c | 2 +-
> fs/cachefiles/namei.c | 2 +-
> fs/coda/dir.c | 4 +--
> fs/ecryptfs/file.c | 4 +--
> fs/ext2/file.c | 4 +--
> fs/ext4/file.c | 6 ++--
> fs/f2fs/file.c | 4 +--
> fs/file.c | 13 +++++++
> fs/fuse/dax.c | 2 +-
> fs/fuse/file.c | 4 +--
> fs/gfs2/file.c | 2 +-
> fs/hugetlbfs/inode.c | 2 +-
> fs/inode.c | 10 +++---
> fs/internal.h | 8 +++++
> fs/namei.c | 4 +--
> fs/nfsd/vfs.c | 2 +-
> fs/nilfs2/file.c | 2 +-
> fs/orangefs/file.c | 2 +-
> fs/orangefs/inode.c | 2 +-
> fs/overlayfs/file.c | 2 +-
> fs/overlayfs/inode.c | 2 +-
> fs/pipe.c | 2 +-
> fs/ramfs/file-nommu.c | 2 +-
> fs/readdir.c | 61 +++++++++++++++++++++++++--------
> fs/smb/client/cifsfs.c | 2 +-
> fs/splice.c | 2 +-
> fs/stat.c | 2 +-
> fs/ubifs/file.c | 2 +-
> fs/udf/file.c | 2 +-
> fs/xfs/libxfs/xfs_alloc.c | 2 +-
> fs/xfs/libxfs/xfs_attr_remote.c | 2 +-
> fs/xfs/libxfs/xfs_btree.c | 2 +-
> fs/xfs/libxfs/xfs_da_btree.c | 16 +++++++++
> fs/xfs/libxfs/xfs_da_btree.h | 1 +
> fs/xfs/libxfs/xfs_dir2_block.c | 7 ++--
> fs/xfs/libxfs/xfs_dir2_priv.h | 2 +-
> fs/xfs/libxfs/xfs_shared.h | 2 ++
> fs/xfs/libxfs/xfs_trans_inode.c | 12 +++++--
> fs/xfs/scrub/dir.c | 2 +-
> fs/xfs/scrub/readdir.c | 2 +-
> fs/xfs/scrub/repair.c | 2 +-
> fs/xfs/xfs_buf.c | 43 +++++++++++++++++------
> fs/xfs/xfs_buf.h | 4 +--
> fs/xfs/xfs_buf_item.c | 9 +++--
> fs/xfs/xfs_buf_item.h | 2 +-
> fs/xfs/xfs_buf_item_recover.c | 2 +-
> fs/xfs/xfs_dir2_readdir.c | 49 ++++++++++++++++++++------
> fs/xfs/xfs_dquot.c | 2 +-
> fs/xfs/xfs_file.c | 6 ++--
> fs/xfs/xfs_inode.c | 27 +++++++++++++++
> fs/xfs/xfs_inode.h | 17 +++++----
> fs/xfs/xfs_inode_item.c | 12 ++++---
> fs/xfs/xfs_inode_item.h | 3 +-
> fs/xfs/xfs_iops.c | 31 ++++++++++++++---
> fs/xfs/xfs_log.c | 33 ++++++++++++------
> fs/xfs/xfs_log.h | 5 +--
> fs/xfs/xfs_log_cil.c | 17 +++++++--
> fs/xfs/xfs_log_priv.h | 4 +--
> fs/xfs/xfs_trans.c | 44 ++++++++++++++++++++----
> fs/xfs/xfs_trans.h | 2 +-
> fs/xfs/xfs_trans_buf.c | 18 ++++++++--
> fs/zonefs/file.c | 4 +--
> include/linux/file.h | 7 ++++
> include/linux/fs.h | 16 +++++++--
> include/uapi/linux/io_uring.h | 1 +
> io_uring/fs.c | 53 ++++++++++++++++++++++++++++
> io_uring/fs.h | 3 ++
> io_uring/opdef.c | 8 +++++
> kernel/bpf/inode.c | 4 +--
> mm/filemap.c | 8 ++---
> mm/shmem.c | 6 ++--
> net/unix/af_unix.c | 4 +--
> 75 files changed, 499 insertions(+), 161 deletions(-)
>
> --
> 2.25.1
>