lkml.org 
[lkml]   [2005]   [Jun]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
Subject[PATCH] VFS mpage.c:mpage_end_io_read wrong behavior when I/O failure occurs
From
Related FS:
JFS

Related files:
fs/mpage.c

Bug description:
Make a partition in USB storage HDD, create a test file with
any contents.
Write a program, do: open(O_RDWR) - write - fsync - close.
After each operation, pause for a while, such as 3 seconds. Between
open and fsync, unplug USB wire to force an I/O error. fsync will
return OK instead of EIO.

Bug analysis:
sys_fsync does 3 jobs:
1)submit all pages taged with PAGECACHE_TAG_DIRTY to disk I/O,
2)do file-system related fsync operations
3)wait all pages taged with PAGECACHE_TAG_WRITEBACK to complete.
Here, all disk I/O are asynchronous, when finished, mpage_end_io_write
will remove page from mapping's PAGECACHE_TAG_WRITEBACK tree. If I/O
fails, it will also set PG_error flag, but it FORGET to set the
mapping->flags AS_EIO flag. So in step 3, sys_fsync won't notice these
pages, then no error returns.
static int mpage_end_io_write(...)
{
...
if (!uptodate)
SetPageError(page);<-- Not set mapping->flags
...
}

static int wait_on_page_writeback_range(struct address_space *mapping,
pgoff_t start, pgoff_t end)
{
...
int ret = 0;
...

while ((index <= end) && <-- For I/O error page, no loop here
(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
PAGECACHE_TAG_WRITEBACK,
min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
...
}

if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
ret = -ENOSPC;
if (test_and_clear_bit(AS_EIO, &mapping->flags)) <-- Not set
ret = -EIO;

return ret; <-- return 0
}

Way around:
Set AS_EIO to mapping->flags if I/O error happens.

Patch:
diff -uNp linux-2.6.11.11-orig/fs/mpage.c linux-2.6.11.11-new/fs/mpage.c
--- linux-2.6.11.11-orig/fs/mpage.c 2005-05-27 01:06:46.000000000 -0400
+++ linux-2.6.11.11-new/fs/mpage.c 2005-06-02 14:29:42.264334920 -0400
@@ -79,8 +79,11 @@ static int mpage_end_io_write(struct bio
if (--bvec >= bio->bi_io_vec)
prefetchw(&bvec->bv_page->flags);

- if (!uptodate)
+ if (!uptodate){
SetPageError(page);
+ if(page->mapping)
+ set_bit(AS_EIO, &page->mapping->flags);
+ }
end_page_writeback(page);
} while (bvec >= bio->bi_io_vec);
bio_put(bio);

Signed-off-by: Qu Fuping<fs@ercist.iscas.ac.cn>

-
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: 2005-06-02 09:54    [W:0.035 / U:36.108 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site