Fork of alistair23 Linux kernel for reMarkable from https://github.com/alistair23/linux
![]() In end_bio_extent_readpage() we had a strange dance around extent_start/extent_len. Hidden behind the strange dance is, it's just calling endio_readpage_release_extent() on each bvec range. Here is an example to explain the original work flow: Bio is for inode 257, containing 2 pages, for range [1M, 1M+8K) end_bio_extent_extent_readpage() entered |- extent_start = 0; |- extent_end = 0; |- bio_for_each_segment_all() { | |- /* Got the 1st bvec */ | |- start = SZ_1M; | |- end = SZ_1M + SZ_4K - 1; | |- update = 1; | |- if (extent_len == 0) { | | |- extent_start = start; /* SZ_1M */ | | |- extent_len = end + 1 - start; /* SZ_1M */ | | } | | | |- /* Got the 2nd bvec */ | |- start = SZ_1M + 4K; | |- end = SZ_1M + 4K - 1; | |- update = 1; | |- if (extent_start + extent_len == start) { | | |- extent_len += end + 1 - start; /* SZ_8K */ | | } | } /* All bio vec iterated */ | |- if (extent_len) { |- endio_readpage_release_extent(tree, extent_start, extent_len, update); /* extent_start == SZ_1M, extent_len == SZ_8K, uptodate = 1 */ As the above flow shows, the existing code in end_bio_extent_readpage() is accumulates extent_start/extent_len, and when the contiguous range stops, calls endio_readpage_release_extent() for the range. However current behavior has something not really considered: - The inode can change For bio, its pages don't need to have contiguous page_offset. This means, even pages from different inodes can be packed into one bio. - bvec cross page boundary There is a feature called multi-page bvec, where bvec->bv_len can go beyond bvec->bv_page boundary. - Poor readability This patch will address the problem: - Introduce a proper structure, processed_extent, to record processed extent range - Integrate inode/start/end/uptodate check into endio_readpage_release_extent() - Add more comment on each step. This should greatly improve the readability, now in end_bio_extent_readpage() there are only two endio_readpage_release_extent() calls. - Add inode check for contiguity Now we also ensure the inode is the same one before checking if the range is contiguous. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Qu Wenruo <wqu@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com> |
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arch | ||
block | ||
certs | ||
crypto | ||
Documentation | ||
drivers | ||
fs | ||
include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
LICENSES | ||
mm | ||
net | ||
samples | ||
scripts | ||
security | ||
sound | ||
tools | ||
usr | ||
virt | ||
.clang-format | ||
.cocciconfig | ||
.get_maintainer.ignore | ||
.gitattributes | ||
.gitignore | ||
.mailmap | ||
COPYING | ||
CREDITS | ||
Kbuild | ||
Kconfig | ||
MAINTAINERS | ||
Makefile | ||
README |
Linux kernel ============ There are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. Please read Documentation/admin-guide/README.rst first. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. The formatted documentation can also be read online at: 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. 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.