On 08/21/2014 05:05 PM, Ivan Shapovalov wrote:
On Thursday 21 August 2014 at 00:30:45, Edward Shishkin wrote:
On 08/20/2014 10:34 PM, Ivan Shapovalov wrote:
On Wednesday 20 August 2014 at 01:39:42, Edward Shishkin wrote:
On 08/20/2014 12:32 AM, Ivan Shapovalov wrote:
From `git log` I've seen that VFS people intend to replace ->aio_read() and
->aio_write() of struct file_operations with new methods ->read_iter() and
->write_iter().
(Along with a couple of related new helpers, differing from previous just in
calling _iter methods instead of aio_ ones.)
From other filesystems it seems that these are simple drop-in replacements
(however, well, I have zero familiarity with VFS). So here is a question:
is there any intentional reason that generic_file_aio_write() is not used
in reiser4?
Currently reiser4 is a set of two filesystems which differ in methods
of handling regular files. For VFS we provide "dispatchers", which pass
management to appropriate plugin (UNIX_FILE or CRYPTCOMPRESS).
UNIX_FILE plugin doesn't use generic write for performance reasons
(I'll try to find the respective mailing thread).
This mailing thread sheds the light on why we don't want to use generic
write:
(this in only FYI, don't try to make friendship between reiser4 and VFS :))
http://markmail.org/message/ydzplf6bxokfgkch#query:+page:1+mid:appoj72tdeop3f7f+state:results
CRYPTCOMPRESS doesn't
use it for compatibility reasons: I don't know how how to rewrite it
gracefully using the generic write method.
Edward.
Thanks for explanation! So, does this patch make any sense?
I haven't looked at this carefully yet, but likely it is correct.
Thanks,
Edward.
Turned out it isn't.. The iter_file_splice_write() requires ->write_iter
to be set, or a NULL dereference happens.
At first I've thought that we're out of luck and will need to use the fallback
splice implementation (default_file_splice_write), but just setting
->write_iter to generic_file_write_iter strangely worked.
(By "it works" I mean "splice finishes successfully and does not cause data
corruptions").
Could you please comment on this? :)
Thanks,
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