Documentation/filesystems/netfs_library.rst

1 .. SPDX-License-Identifier: GPL-2.0
9  - Overview.
10  - Per-inode context.
11    - Inode context helper functions.
12  - Buffered read helpers.
13    - Read helper functions.
14    - Read helper structures.
15    - Read helper operations.
16    - Read helper procedure.
17    - Read helper cache API.
25 just includes turning various VM buffered read operations into requests to read
33 Per-Inode Context
76 ------------------------------
78 To help deal with the per-inode context, a number helper functions are
95 Buffered Read Helpers
98 The library provides a set of read helpers that handle the ->read_folio(),
99 ->readahead() and much of the ->write_begin() VM operations and translate them
116  * Handle local caching, allowing cached data and server-read data to be
133 ---------------------
149 state in the per-inode context.
151 For ->readahead() and ->read_folio(), the network filesystem just point directly
152 at the corresponding read helper; whereas for ->write_begin(), it may be a
161 If an error occurs, the ->free_request() will be called to clean up the
173 of bytes transferred or a negative error code, plus a flag indicating whether
174 the operation was asynchronous (ie. whether the follow-on processing can be
179 ----------------------
203    may or may not point to inode->i_data.
218    may be altered by the ->expand_readahead() op.
290 ----------------------
327    Expansion is communicated by changing ->start and ->len in the request
328    structure.  Note that if any change is made, ->len must be increased by at
329    least as much as ->start is reduced.
343    reading.  In the subrequest, ->start, ->len and ->transferred indicate what
349    uptodate, unlocking them or dropping their refs - the helpers need to deal
382 ---------------------
442 ---------------------
528    downloaded from the server or read from the cache - or whether slicing
533    [Required] Called to configure the next slice of a request.  ->start and
534    ->len in the subrequest indicate where and how big the next slice can be;
558    caller is certain that no data has been written to that region - for example
581    It returns 0 if some data was found, -ENODATA if there was no usable data
582    within the region or -ENOBUFS if there is no caching on this file.
593 .. kernel-doc:: include/linux/netfs.h
594 .. kernel-doc:: fs/netfs/buffered_read.c