1 .. SPDX-License-Identifier: GPL-2.0
2
3 ==============
4 Fuse I/O Modes
5 ==============
6
7 Fuse supports the following I/O modes:
8
9 - direct-io
10 - cached
11 + write-through
12 + writeback-cache
13
14 The direct-io mode can be selected with the FO
15 FUSE_OPEN reply.
16
17 In direct-io mode the page cache is completely
18 No read-ahead takes place. Shared mmap is disa
19 mmap, the FUSE_DIRECT_IO_ALLOW_MMAP flag may b
20
21 In cached mode reads may be satisfied from the
22 read-ahead by the kernel to fill the cache. T
23 after any writes to the file. All mmap modes
24
25 The cached mode has two sub modes controlling
26 write-through mode is the default and is suppo
27 writeback-cache mode may be selected by the FU
28 FUSE_INIT reply.
29
30 In write-through mode each write is immediatel
31 WRITE requests, as well as updating any cached
32 uncached, but fully written pages). No READ r
33 so when an uncached page is partially written,
34
35 In writeback-cache mode (enabled by the FUSE_W
36 the cache only, which means that the write(2)
37 fast. Dirty pages are written back implicitly
38 reclaim on memory pressure) or explicitly (inv
39 when the last ref to the file is being release
40 assumes that all changes to the filesystem go
41 (size and atime/ctime/mtime attributes are kep
42 it's generally not suitable for network filesy
43 written, then the page needs to be first read
44 even for files opened for O_WRONLY it is possi
45 generated by the kernel.
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