mirror of
https://github.com/rd-stuffs/msm-4.14.git
synced 2025-02-20 11:45:48 +08:00
a1b7a4dea6
There is a race window between write_cache_pages calling clear_page_dirty_for_io and XFS calling set_page_writeback, in which the mapping for an inode is tagged neither as dirty, nor as writeback. If the COW shrinker hits in exactly that window we'll remove the delayed COW extents and writepages trying to write it back, which in release kernels will manifest as corruption of the bmap btree, and in debug kernels will trip the ASSERT about now calling xfs_bmapi_write with the COWFORK flag for holes. A complex customer load manages to hit this window fairly reliably, probably by always having COW writeback in flight while the cow shrinker runs. This patch adds another check for having the I_DIRTY_PAGES flag set, which is still set during this race window. While this fixes the problem I'm still not overly happy about the way the COW shrinker works as it still seems a bit fragile. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.