From: Badari Pulavarty <pbadari@us.ibm.com>
I found one more accounting inconsistency with dio_pages_in_io. This is a
day-one bug and I started hitting it on latest -mm due to the recent
changes to dio_pages_in_io calculations to be exact.
If the file is badly fragmented (no contiguous blocks at all), and the user
buffer is not page aligned - we need to create IO for each disk block with
2 pages. (bio with 2 vecs).
dio_bio_add_page() should not decrement dio_pages_in_io for every add page.
It should only decrement, it only if its done with that page and moving on
to next page. (since dio_pages_in_io represent how many actual pages we
are operating on).
Here is the patch to fix this accounting. Without this patch, we will hit
BUG() in dio_new_bio() with O_DIRECT on filesystems.
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/fs/direct-io.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletion(-)
diff -puN fs/direct-io.c~dio-pages-in-io-accounting-fix fs/direct-io.c
--- 25/fs/direct-io.c~dio-pages-in-io-accounting-fix 2004-08-16 11:51:25.669776408 -0700
+++ 25-akpm/fs/direct-io.c 2004-08-16 11:51:25.673775800 -0700
@@ -561,7 +561,11 @@ static int dio_bio_add_page(struct dio *
ret = bio_add_page(dio->bio, dio->cur_page,
dio->cur_page_len, dio->cur_page_offset);
if (ret == dio->cur_page_len) {
- dio->pages_in_io--;
+ /*
+ * Decrement count only, if we are done with this page
+ */
+ if ((dio->cur_page_len + dio->cur_page_offset) == PAGE_SIZE)
+ dio->pages_in_io--;
page_cache_get(dio->cur_page);
dio->final_block_in_bio = dio->cur_page_block +
(dio->cur_page_len >> dio->blkbits);
_