lkml.org 
[lkml]   [2003]   [Aug]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Spurious -EIO when reading a file being written with O_DIRECT?
Oleg Drokin <green@namesys.com> wrote:
>
> We were reported a problem where if a file being written in directio mode
> and being read at the same time (in "normal/buffered" mode), then reading
> process gets -EIO when near the end of file.
>
> Initially I thought this is reiserfs-only problemm and digged in that
> direction, but then it turned out reiserfs does everything correctly
> and the VFS itself seems to be racey (my current suspiction is directio
> process uses get_block() that extends the file <schedule> reading process
> gets the buffer and submits io, then waits for page to become uptodate
> <schedule> direct io process unmaps buffer's metadata
> As a result - that page never becomes uptodate and we get -EIO from do_generic_file_read. )
> If I take i_sem around call to do_generic_file_read in generic_file_read (in 2.4.21-pre10),
> that of course helps (this is of course not a correct fix, but just a demonstration
> that some VFS race is in place).
> The same problem can be observed on ext2 in both 2.4.21-pre10 and in 2.6.0-test2
> Attached is test_directio.c program, compile it and run with some filename as argument,
> immediately start "tail" with same filename and you'd get almost immediate
> I/O error from tail on 2.4 and you'd get same I/O error in 2.6 only after some more waiting.
>
> Is this something known and expected (or may be somebody have a fix already? ;) )?

Test a current 2.4 kernel - it has lots of redone O_DIRECT-vs-buffered
locking.

A 2.6 forward-port of that was done by Badari but I lost it and need to
find it again.


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:47    [W:0.034 / U:7.524 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site