There is a bug in direct-io on propagating write error up to the higher I/O
layer. When performing an async ODIRECT write to a block device, if a
device error occurred (like media error or disk is pulled), the error code
is only propagated from device driver to the DIO layer. The error code
stops at finished_one_bio(). The aysnc write, however, is supposedly have
a corresponding AIO event with appropriate return code (in this case -EIO).
Application which waits on the async write event, will hang forever since
such AIO event is lost forever (if such app did not use the timeout option
in io_getevents call. Regardless, an AIO event is lost).
The discovery of above bug leads to another discovery of potential race
window with dio->result. The fundamental problem is that dio->result is
overloaded with dual use: an indicator of fall back path for partial dio
write, and an error indicator used in the I/O completion path. In the
event of device error, the setting of -EIO to dio->result clashes with
value used to track partial write that activates the fall back path.
It was also pointed out that it is impossible to use dio->result to track
partial write and at the same time to track error returned from device
driver. Because direct_io_work can only determines whether it is a partial
write at the end of io submission and in mid stream of those io submission,
a return code could be coming back from the driver. Thus messing up all
the subsequent logic.
Proposed fix is to separating out error code returned by the IO completion
path from partial IO submit tracking. A new variable is added to dio
structure specifically to track io error returned in the completion path.
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Acked-by: Zach Brown <zach.brown@oracle.com>
Acked-by: Suparna Bhattacharya <suparna@in.ibm.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Affects only XFS (i.e. DIO_OWN_LOCKING case) - currently it is
not possible to get i_mutex locking correct when using DIO_OWN
direct I/O locking in a filesystem due to indeterminism in the
possible return code/lock/unlock combinations. This can cause
a direct read to attempt a double i_mutex unlock inside XFS.
We're now ensuring __blockdev_direct_IO always exits with the
inode i_mutex (still) held for a direct reader.
Tested with the three different locking modes (via direct block
device access, ext3 and XFS) - both reading and writing; cannot
find any regressions resulting from this change, and it clearly
fixes the mutex_unlock warning originally reported here:
http://marc.theaimsgroup.com/?l=linux-kernel&m=114189068126253&w=2
Signed-off-by: Nathan Scott <nathans@sgi.com>
Acked-by: Christoph Hellwig <hch@lst.de>
Currently, if you open a file O_DIRECT, truncate it to a size that is not a
multiple of the disk block size, and then try to read the last block in the
file, the read will return 0. The problem is in do_direct_IO, here:
/* Handle holes */
if (!buffer_mapped(map_bh)) {
char *kaddr;
...
if (dio->block_in_file >=
i_size_read(dio->inode)>>blkbits) {
/* We hit eof */
page_cache_release(page);
goto out;
}
We shift off any remaining bytes in the final block of the I/O, resulting
in a 0-sized read. I've attached a patch that fixes this. I'm not happy
about how ugly the math is getting, so suggestions are more than welcome.
I've tested this with a simple program that performs the steps outlined for
reproducing the problem above. Without the patch, we get a 0-sized result
from read. With the patch, we get the correct return value from the short
read.
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Suparna Bhattacharya <suparna@in.ibm.com>
Cc: Mingming Cao <cmm@us.ibm.com>
Cc: Joel Becker <Joel.Becker@oracle.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch converts the inode semaphore to a mutex. I have tested it on
XFS and compiled as much as one can consider on an ia64. Anyway your
luck with it might be different.
Modified-by: Ingo Molnar <mingo@elte.hu>
(finished the conversion)
Signed-off-by: Jes Sorensen <jes@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Remove PageReserved() calls from core code by tightening VM_RESERVED
handling in mm/ to cover PageReserved functionality.
PageReserved special casing is removed from get_page and put_page.
All setting and clearing of PageReserved is retained, and it is now flagged
in the page_alloc checks to help ensure we don't introduce any refcount
based freeing of Reserved pages.
MAP_PRIVATE, PROT_WRITE of VM_RESERVED regions is tentatively being
deprecated. We never completely handled it correctly anyway, and is be
reintroduced in future if required (Hugh has a proof of concept).
Once PageReserved() calls are removed from kernel/power/swsusp.c, and all
arch/ and driver code, the Set and Clear calls, and the PG_reserved bit can
be trivially removed.
Last real user of PageReserved is swsusp, which uses PageReserved to
determine whether a struct page points to valid memory or not. This still
needs to be addressed (a generic page_is_ram() should work).
A last caveat: the ZERO_PAGE is now refcounted and managed with rmap (and
thus mapcounted and count towards shared rss). These writes to the struct
page could cause excessive cacheline bouncing on big systems. There are a
number of ways this could be addressed if it is an issue.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Refcount bug fix for filemap_xip.c
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
XFS will have to look at iocb->private to fix aio+dio. No other filesystem
is using the blockdev_direct_IO* end_io callback.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The direct I/O code is mapping the read request to the file system block. If
the file size was not on a block boundary, the result would show the the read
reading past EOF. This was only happening for the AIO case. The non-AIO case
truncates the result to match file size (in direct_io_worker). This patch
does the same thing for the AIO case, it truncates the result to match the
file size if the read reads past EOF.
When I/O completes the result can be truncated to match the file size
without using i_size_read(), thus the aio result now matches the number of
bytes read to the end of file.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Chen, Kenneth W