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With the existing fscrypt IV generation methods, each file's data blocks
have contiguous DUNs. Therefore the direct I/O code "just worked"
because it only submits logically contiguous bios. But with
IV_INO_LBLK_32, the direct I/O code breaks because the DUN can wrap from
0xffffffff to 0. We can't submit bios across such boundaries.
This is especially difficult to handle when block_size != PAGE_SIZE,
since in that case the DUN can wrap in the middle of a page. Punt on
this case for now and just handle block_size == PAGE_SIZE.
Add and use a new function fscrypt_dio_supported() to check whether a
direct I/O request is unsupported due to encryption constraints.
Then, update fs/direct-io.c (used by f2fs, and by ext4 in kernel v5.4
and earlier) and fs/iomap/direct-io.c (used by ext4 in kernel v5.5 and
later) to avoid submitting I/O across a DUN discontinuity.
(This is needed in ACK now because ACK already supports direct I/O with
inline crypto. I'll be sending this upstream along with the encrypted
direct I/O support itself once its prerequisites are closer to landing.)
(cherry picked from android-mainline commit
8d6c90c9d6)
Conflicts:
fs/ext4/file.c
fs/iomap/direct-io.c
(Dropped the iomap changes because in kernel v5.4 and earlier,
ext4 doesn't use iomap for direct I/O)
Test: For now, just manually tested direct I/O on ext4 and f2fs in the
DUN discontinuity case.
Bug: 144046242
Change-Id: I0c0b0b20a73ade35c3660cc6f9c09d49d3853ba5
Signed-off-by: Eric Biggers <ebiggers@google.com>
Linux kernel
============
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In order to build the documentation, use ``make htmldocs`` or
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https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.