[PATCH 00/19] netfs: Prep for write helpers
David Howells
dhowells at redhat.com
Wed Mar 2 06:01:41 PST 2022
Having had a go at implementing write helpers and content encryption
support in netfslib, it seems that the netfs_read_{,sub}request structs and
the equivalent write request structs were almost the same and so should be
merged, thereby requiring only one set of alloc/get/put functions and a
common set of tracepoints.
Merging the structs also has the advantage that if a bounce buffer is added
to the request struct, a read operation can be performed to fill the bounce
buffer, the contents of the buffer can be modified and then a write
operation can be performed on it to send the data wherever it needs to go
using the same request structure all the way through. The I/O handlers
would then transparently perform any required crypto. This should make it
easy to perform RMW cycles if needed.
The potentially common functions and structs, however, by their names all
proclaim themselves to be associated with the read side of things. The
bulk of these changes alter this in the following ways:
(1) Rename struct netfs_read_{,sub}request to netfs_io_{,sub}request.
(2) Rename some enums, members and flags to make them more appropriate.
(3) Adjust some comments to match.
(4) Drop "read"/"rreq" from the names of common functions. For instance,
netfs_get_read_request() becomes netfs_get_request().
(5) The ->init_rreq() and ->issue_op() methods become ->init_request() and
->issue_read(). I've kept the latter as a read-specific function and
in another branch added an ->issue_write() method.
The driver source is then reorganised into a number of files:
fs/netfs/buffered_read.c Create read reqs to the pagecache
fs/netfs/io.c Dispatchers for read and write reqs
fs/netfs/main.c Some general miscellaneous bits
fs/netfs/objects.c Alloc, get and put functions
fs/netfs/stats.c Optional procfs statistics.
and future development can be fitted into this scheme, e.g.:
fs/netfs/buffered_write.c Modify the pagecache
fs/netfs/buffered_flush.c Writeback from the pagecache
fs/netfs/direct_read.c DIO read support
fs/netfs/direct_write.c DIO write support
fs/netfs/unbuffered_write.c Write modifications directly back
Beyond the above changes, there are also some changes that affect how
things work:
(1) Make fscache_end_operation() generally available.
(2) In the netfs tracing header, generate enums from the symbol -> string
mapping tables rather than manually coding them.
(3) Add a struct for filesystems that uses netfslib to put into their
inode wrapper structs to hold extra state that netfslib is interested
in, such as the fscache cookie. This allows netfslib functions to be
set in filesystem operation tables and jumped to directly without
having to have a filesystem wrapper.
(4) Add a member to the struct added in (3) to track the remote inode
length as that may differ if local modifications are buffered. We may
need to supply an appropriate EOF pointer when storing data (in AFS
for example).
(5) Pass extra information to netfs_alloc_request() so that the
->init_request() hook can access it and retain information to indicate
the origin of the operation.
(6) Make the ->init_request() hook return an error, thereby allowing a
filesystem that isn't allowed to cache an inode (ceph or cifs, for
example) to skip readahead.
(7) Switch to using refcount_t for subrequests and add tracepoints to log
refcount changes for the request and subrequest structs.
(8) Add a function to consolidate dispatching a read request. Similar
code is used in three places and another couple are likely to be added
in the future.
The patches can be found on this branch:
http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=fscache-next
This is based on top of ceph's master branch as some of the patches
conflict.
David
---
David Howells (17):
netfs: Generate enums from trace symbol mapping lists
netfs: Add a netfs inode context
netfs: Rename netfs_read_*request to netfs_io_*request
netfs: Finish off rename of netfs_read_request to netfs_io_request
netfs: Split netfs_io_* object handling out
netfs: Adjust the netfs_rreq tracepoint slightly
netfs: Trace refcounting on the netfs_io_request struct
netfs: Trace refcounting on the netfs_io_subrequest struct
netfs: Adjust the netfs_failure tracepoint to indicate non-subreq lines
netfs: Prepare to split read_helper.c
netfs: Add a function to consolidate beginning a read
netfs: Split fs/netfs/read_helper.c
netfs: Split some core bits out into their own file
netfs: Rename rename read_helper.c to io.c
netfs: Change ->init_rreq() to return an error code
netfs: Keep track of the actual remote file size
afs: Maintain netfs_i_context::remote_i_size
Jeff Layton (1):
netfs: Refactor arguments for netfs_alloc_read_request
Jeffle Xu (1):
fscache: export fscache_end_operation()
Documentation/filesystems/netfs_library.rst | 38 +-
fs/9p/cache.c | 10 +-
fs/9p/v9fs.c | 4 +-
fs/9p/v9fs.h | 12 +-
fs/9p/vfs_addr.c | 60 +-
fs/9p/vfs_inode.c | 13 +-
fs/afs/dynroot.c | 1 +
fs/afs/file.c | 41 +-
fs/afs/inode.c | 32 +-
fs/afs/internal.h | 23 +-
fs/afs/super.c | 4 +-
fs/afs/write.c | 10 +-
fs/cachefiles/io.c | 10 +-
fs/ceph/addr.c | 45 +-
fs/ceph/cache.c | 28 +-
fs/ceph/cache.h | 15 +-
fs/ceph/inode.c | 6 +-
fs/ceph/super.h | 16 +-
fs/cifs/cifsglob.h | 10 +-
fs/cifs/fscache.c | 19 +-
fs/cifs/fscache.h | 2 +-
fs/fscache/internal.h | 11 -
fs/netfs/Makefile | 8 +-
fs/netfs/buffered_read.c | 429 +++++++
fs/netfs/internal.h | 49 +-
fs/netfs/io.c | 656 ++++++++++
fs/netfs/main.c | 20 +
fs/netfs/objects.c | 161 +++
fs/netfs/read_helper.c | 1205 -------------------
fs/netfs/stats.c | 1 -
fs/nfs/fscache.c | 8 -
include/linux/fscache.h | 14 +
include/linux/netfs.h | 162 ++-
include/trace/events/cachefiles.h | 6 +-
include/trace/events/netfs.h | 188 ++-
35 files changed, 1750 insertions(+), 1567 deletions(-)
create mode 100644 fs/netfs/buffered_read.c
create mode 100644 fs/netfs/io.c
create mode 100644 fs/netfs/main.c
create mode 100644 fs/netfs/objects.c
delete mode 100644 fs/netfs/read_helper.c
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