mirror of
https://github.com/hardkernel/linux.git
synced 2026-06-07 11:26:02 +09:00
04414e4692
commit 8c4e0f2123 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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 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.