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This is a preparatory patch for fixing zero padding issues in concurrent append write scenarios. In the following patches, we need to obtain byte-granular writeback end position for io_size trimming after EOF handling. Due to concurrent writeback and truncate operations, inode size may shrink. Resampling inode size would force writeback code to handle the newly appeared post-EOF blocks, which is undesirable. As Dave explained in [1]: "Really, the issue is that writeback mappings have to be able to handle the range being mapped suddenly appear to be beyond EOF. This behaviour is a longstanding writeback constraint, and is what iomap_writepage_handle_eof() is attempting to handle. We handle this by only sampling i_size_read() whilst we have the folio locked and can determine the action we should take with that folio (i.e. nothing, partial zeroing, or skip altogether). Once we've made the decision that the folio is within EOF and taken action on it (i.e. moved the folio to writeback state), we cannot then resample the inode size because a truncate may have started and changed the inode size." To avoid resampling inode size after EOF handling, we convert end_pos to byte-granular writeback position and return it from EOF handling function. Since iomap_set_range_dirty() can handle unaligned lengths, this conversion has no impact on it. However, iomap_find_dirty_range() requires aligned start and end range to find dirty blocks within the given range, so the end position needs to be rounded up when passed to it. LINK [1]: https://lore.kernel.org/linux-xfs/Z1Gg0pAa54MoeYME@localhost.localdomain/ Signed-off-by: Long Li <leo.lilong@huawei.com> Link: https://lore.kernel.org/r/20241209114241.3725722-2-leo.lilong@huawei.com Reviewed-by: Brian Foster <bfoster@redhat.com> Signed-off-by: Christian Brauner <brauner@kernel.org>
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 reStructuredText 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.