No description
  • C 96.8%
  • Assembly 0.9%
  • Rust 0.7%
  • Shell 0.6%
  • Python 0.5%
  • Other 0.3%
Find a file
Brian Foster eb65540aa9
iomap: warn on zero range of a post-eof folio
iomap_zero_range() uses buffered writes for manual zeroing, no
longer updates i_size for such writes, but is still explicitly
called for post-eof ranges. The historical use case for this is
zeroing post-eof speculative preallocation on extending writes from
XFS. However, XFS also recently changed to convert all post-eof
delalloc mappings to unwritten in the iomap_begin() handler, which
means it now never expects manual zeroing of post-eof mappings. In
other words, all post-eof mappings should be reported as holes or
unwritten.

This is a subtle dependency that can be hard to detect if violated
because associated codepaths are likely to update i_size after folio
locks are dropped, but before writeback happens to occur. For
example, if XFS reverts back to some form of manual zeroing of
post-eof blocks on write extension, writeback of those zeroed folios
will now race with the presumed i_size update from the subsequent
buffered write.

Since iomap_zero_range() can't correctly zero post-eof mappings
beyond EOF without updating i_size, warn if this ever occurs. This
serves as minimal indication that if this use case is reintroduced
by a filesystem, iomap_zero_range() might need to reconsider i_size
updates for write extending use cases.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Link: https://lore.kernel.org/r/20241115145931.535207-1-bfoster@redhat.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
History 2024-11-21 09:35:24 +01:00
arch
block
certs
crypto
Documentation
drivers
fs
include
init
io_uring
ipc
kernel
lib
LICENSES
mm
net
rust
samples
scripts
security
sound
tools
usr
virt
.clang-format
.cocciconfig
.editorconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
.rustfmt.toml
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 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.