If block_read_full_page() detects an error when running get_block() it will
run SetPageError(), then it will zero out the block in pagecache and will mark
the buffer_head uptodate.
So at the end of readahead we end up with a non-uptodate pagecache page which
is marked PageError. But it has uptodate buffers.
The pagefault code will run ClearPageError, will launch readpage a second time
and block_read_full_page() will notice the uptodate buffers and will mark the
page uptodate as well. We end up with an uptodate, !PageError page full of
zeros and the error is lost.
(It seems a little odd that filemap_nopage() runs ClearPageError(). I guess
all of this adds up to meaning that for each attempted access to the page, the
pagefault handler will retry the I/O. Which is good and bad. If the app is
ignoring SIGBUS for some reason we could get a lot of back-to-back I/O
errors.)
Fix it by not marking the pagecache buffer_head as uptodate if the attempt to
map that buffer to a disk block failed.
Credit-to: Qu Fuping <fs@ercist.iscas.ac.cn>
For reporting the bug and identifying its source.
Signed-off-by: Qu Fuping <fs@ercist.iscas.ac.cn>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch makes some needlessly global identifiers static.
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: Arjan van de Ven <arjanv@infradead.org>
Acked-by: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The `last_bh' logic probably isn't worth much. In those situations where only
the front part of the page is being written out we will save some looping but
in the vastly more common case of an all-page writeout if just adds more code.
Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Remove all those get_bh()'s and put_bh()'s by extending lock_page() to cover
the troublesome regions.
(get_bh() and put_bh() happen every time whereas contention on a page's lock
in there happens basically never).
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
When running
fsstress -v -d $DIR/tmp -n 1000 -p 1000 -l 2
on an ext2 filesystem with 1024 byte block size, on SMP i386 with 4096 byte
page size over loopback to an image file on a tmpfs filesystem, I would
very quickly hit
BUG_ON(!buffer_async_write(bh));
in fs/buffer.c:end_buffer_async_write
It seems that more than one request would be submitted for a given bh
at a time.
What would happen is the following:
2 threads doing __mpage_writepages on the same page.
Thread 1 - lock the page first, and enter __block_write_full_page.
Thread 1 - (eg.) mark_buffer_async_write on the first 2 buffers.
Thread 1 - set page writeback, unlock page.
Thread 2 - lock page, wait on page writeback
Thread 1 - submit_bh on the first 2 buffers.
=> both requests complete, none of the page buffers are async_write,
end_page_writeback is called.
Thread 2 - wakes up. enters __block_write_full_page.
Thread 2 - mark_buffer_async_write on (eg.) the last buffer
Thread 1 - finds the last buffer has async_write set, submit_bh on that.
Thread 2 - submit_bh on the last buffer.
=> oops.
So change __block_write_full_page to explicitly keep track of the last bh
we need to issue, so we don't touch anything after issuing the last
request.
Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Fix a race where __block_prepare_write can leak out an in-flight read
against a bh if get_block returns an error. This can lead to the page
becoming unlocked while the buffer is locked and the read still in flight.
__mpage_writepage BUGs on this condition.
BUG sighted on a 2-way Itanium2 system with 16K PAGE_SIZE running
fsstress -v -d $DIR/tmp -n 1000 -p 1000 -l 2
where $DIR is a new ext2 filesystem with 4K blocks that is quite
small (causing get_block to fail often with -ENOSPC).
Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This makes sure that reclaimable buffer headers and reclaimable inodes
are accounted properly during the overcommit checks.
Signed-off-by: Andrea Arcangeli <andrea@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Some KernelDoc descriptions are updated to match the current code.
No code changes.
Signed-off-by: Martin Waitz <tali@admingilde.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Remove PAGE_BUG - repalce it with BUG and BUG_ON.
Signed-off-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Replace a number of memory barriers with smp_ variants. This means we won't
take the unnecessary hit on UP machines.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
In rare situations, drop_buffers() can be called for a page which has buffers,
but no ->mapping (it was truncated, but the buffers were left behind because
ext3 was still fiddling with them).
But if there was an I/O error in a buffer_head, drop_buffers() will try to get
at the address_space and will oops.
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!
Andrew Morton