8c4e0f2123
1) If remaining ring space before the end of the ring is smaller then the next cmd to write, tcmu writes a padding entry which fills the remaining space at the end of the ring. Then tcmu calls tcmu_flush_dcache_range() with the size of struct tcmu_cmd_entry as data length to flush. If the space filled by the padding was smaller then tcmu_cmd_entry, tcmu_flush_dcache_range() is called for an address range reaching behind the end of the vmalloc'ed ring. tcmu_flush_dcache_range() in a loop calls flush_dcache_page(virt_to_page(start)); for every page being part of the range. On x86 the line is optimized out by the compiler, as flush_dcache_page() is empty on x86. But I assume the above can cause trouble on other architectures that really have a flush_dcache_page(). For paddings only the header part of an entry is relevant due to alignment rules the header always fits in the remaining space, if padding is needed. So tcmu_flush_dcache_range() can safely be called with sizeof(entry->hdr) as the length here. 2) After it has written a command to cmd ring, tcmu calls tcmu_flush_dcache_range() using the size of a struct tcmu_cmd_entry as data length to flush. But if a command needs many iovecs, the real size of the command may be bigger then tcmu_cmd_entry, so a part of the written command is not flushed then. Link: https://lore.kernel.org/r/20200528193108.9085-1-bstroesser@ts.fujitsu.com Acked-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Bodo Stroesser <bstroesser@ts.fujitsu.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> |
||
|---|---|---|
| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| 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 | ||
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.