mainlining shenanigans
80a2ea9f85
Currently, file system's writepages() function must not fail with an ENOMEM, since if they do, it's possible for buffered data to be lost. This is because on a data integrity writeback writepages() gets called but once, and if it returns ENOMEM, if you're lucky the error will get reflected back to the userspace process calling fsync(). If you aren't lucky, the user is unmounting the file system, and the dirty pages will simply be lost. For this reason, file system code generally will use GFP_NOFS, and in some cases, will retry the allocation in a loop, on the theory that "kernel livelocks are temporary; data loss is forever". Unfortunately, this can indeed cause livelocks, since inside the writepages() call, the file system is holding various mutexes, and these mutexes may prevent the OOM killer from killing its targetted victim if it is also holding on to those mutexes. A better solution would be to allow writepages() to call the memory allocator with flags that give greater latitude to the allocator to fail, and then release its locks and return ENOMEM, and in the case of background writeback, the writes can be retried at a later time. In the case of data-integrity writeback retry after waiting a brief amount of time. Signed-off-by: Theodore Ts'o <tytso@mit.edu> |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.