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SubjectRe: writepage fs corruption fixes
On Fri, Jul 09, 2004 at 06:01:51AM +0200, Andrea Arcangeli wrote:
> --- sles/fs/mpage.c.~1~ 2004-07-05 03:08:08.000000000 +0200
> +++ sles/fs/mpage.c 2004-07-09 05:11:13.543787408 +0200
> @@ -105,7 +105,7 @@ mpage_alloc(struct block_device *bdev,
> bio = bio_alloc(gfp_flags, nr_vecs);
>
> if (bio == NULL && (current->flags & PF_MEMALLOC)) {
> - while (!bio && (nr_vecs /= 2))
> + while (!bio && (nr_vecs /= 2) && nr_vecs)
> bio = bio_alloc(gfp_flags, nr_vecs);
> }
>

the above change is a "noop", the above one wasn't really a bug (I just
misread the code), the rest of the patch is needed. reattached after
filtering out the noop.

--- sles/fs/buffer.c.~1~ 2004-07-05 03:08:09.000000000 +0200
+++ sles/fs/buffer.c 2004-07-09 05:16:47.544011656 +0200
@@ -1586,10 +1586,9 @@ __bread(struct block_device *bdev, secto
EXPORT_SYMBOL(__bread);

/*
- * invalidate_bh_lrus() is called rarely - at unmount. Because it is only for
- * unmount it only needs to ensure that all buffers from the target device are
- * invalidated on return and it doesn't need to worry about new buffers from
- * that device being added - the unmount code has to prevent that.
+ * invalidate_bh_lrus() is called rarely - but not only at unmount.
+ * This doesn't race because it runs in each cpu either in irq
+ * or with preempt disabled.
*/
static void invalidate_bh_lru(void *arg)
{
@@ -1912,19 +1911,19 @@ static int __block_write_full_page(struc

BUG_ON(PageWriteback(page));
set_page_writeback(page); /* Keeps try_to_free_buffers() away */
- unlock_page(page);
-
/*
- * The page may come unlocked any time after the *first* submit_bh()
- * call. Be careful with its buffers.
+ * The page and its bh will not go away from under us
+ * because we pinned all the bh with get_bh and we'll
+ * release them only after we finished.
*/
+ unlock_page(page);
+
do {
struct buffer_head *next = bh->b_this_page;
if (buffer_async_write(bh)) {
submit_bh(WRITE, bh);
nr_underway++;
}
- put_bh(bh);
bh = next;
} while (bh != head);

@@ -1949,6 +1948,15 @@ done:
end_page_writeback(page);
wbc->pages_skipped++; /* We didn't write this page */
}
+
+ /* can finally release the bh and after that the page can be freed */
+ bh = head;
+ do {
+ struct buffer_head *next = bh->b_this_page;
+ put_bh(bh);
+ bh = next;
+ } while (bh != head);
+
return err;

recover:
@@ -1984,7 +1992,6 @@ recover:
submit_bh(WRITE, bh);
nr_underway++;
}
- put_bh(bh);
bh = next;
} while (bh != head);
goto done;
--- sles/fs/mpage.c.~1~ 2004-07-05 03:08:08.000000000 +0200
+++ sles/fs/mpage.c 2004-07-09 05:11:13.543787408 +0200
@@ -520,6 +520,17 @@ alloc_new:
}

/*
+ * Must try to add the page before marking the buffer clean or
+ * the confused fail path above (OOM) will be very confused when
+ * it finds all bh marked clean (i.e. it will not write anything)
+ */
+ length = first_unmapped << blkbits;
+ if (bio_add_page(bio, page, length, 0) < length) {
+ bio = mpage_bio_submit(WRITE, bio);
+ goto alloc_new;
+ }
+
+ /*
* OK, we have our BIO, so we can now mark the buffers clean. Make
* sure to only clean buffers which we know we'll be writing.
*/
@@ -539,12 +550,6 @@ alloc_new:
try_to_free_buffers(page);
}

- length = first_unmapped << blkbits;
- if (bio_add_page(bio, page, length, 0) < length) {
- bio = mpage_bio_submit(WRITE, bio);
- goto alloc_new;
- }
-
BUG_ON(PageWriteback(page));
set_page_writeback(page);
unlock_page(page);
-
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