* [PATCH] 2.6.8-rc4-mm1 DIO pages-in-io accounting fix
@ 2004-08-16 17:50 Badari Pulavarty
0 siblings, 0 replies; only message in thread
From: Badari Pulavarty @ 2004-08-16 17:50 UTC (permalink / raw)
To: akpm; +Cc: linux-kernel
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Hi Andrew,
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,.
Thanks,
Badari
[-- Attachment #2: dio_inio.patch --]
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--- linux.org/fs/direct-io.c 2004-08-16 10:57:33.112528208 -0700
+++ linux-2.6.8-rc4-mm1/fs/direct-io.c 2004-08-16 10:59:10.668697416 -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);
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2004-08-16 17:50 [PATCH] 2.6.8-rc4-mm1 DIO pages-in-io accounting fix Badari Pulavarty
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