filesystems/iomap/porting.rst

1 .. SPDX-License-Identifier: GPL-2.0
27     This worked well enough for direct/indirect-mapped filesystems such
28     as ext2, but is very inefficient for extent-based filesystems such
34  3. Direct access to storage on memory-like devices (fsdax) is only
40     No ->write_begin(), ->write_end() or direct_IO
49 Build the kernel, run fstests with the ``-g all`` option across a wide
53 The recommended approach is first to implement ``->iomap_begin`` (and
54 ``->iomap_end`` if necessary) to allow iomap to obtain a read-only
56 In most cases, this is a relatively trivial conversion of the existing
57 ``get_block()`` function for read-only mappings.
62 other read-only mapping operations will do the right thing.
65 implementation to use the new ``->iomap_begin`` implementation to map
69 It is necessary to write some code to fill out the bufferhead-based
73 Once the read-only functions are working like this, convert each high
77 You *do* have a regression test baseline for fstests, right?
85 At this point, you should look over your ``->iomap_begin`` function.
88 per-operation iomap ops with smaller, more cohesive functions.
92 functionality in the ``->iomap_begin``/``->iomap_end`` methods.
104 Most likely at this point, the buffered read and write paths will still