Re: [PATCH] xfs: shutdown on failure to add page to log bio

Brian Foster
2020-03-25T11:25:08Z

On Wed, Mar 25, 2020 at 12:12:25AM -0700, Christoph Hellwig wrote:
> On Tue, Mar 24, 2020 at 12:57:00PM -0400, Brian Foster wrote:
> > Rather than warn about writing out a corrupted log buffer, shutdown
> > the fs as is done for any log I/O related error. This preserves the
> > consistency of the physical log such that log recovery succeeds on a
> > subsequent mount. Note that this was observed on a 64k page debug
> > kernel without upstream commit 59bb47985c1d ("mm, sl[aou]b:
> > guarantee natural alignment for kmalloc(power-of-two)"), which
> > demonstrated frequent iclog bio overflows due to unaligned (slab
> > allocated) iclog data buffers.
>
> Weird..
>
> > static void
> > xlog_map_iclog_data(
> > - struct bio *bio,
> > - void *data,
> > + struct xlog_in_core *iclog,
> > size_t count)
> > {
> > + struct xfs_mount *mp = iclog->ic_log->l_mp;
> > + struct bio *bio = &iclog->ic_bio;
> > + void *data = iclog->ic_data;
> > +
> > do {
> > struct page *page = kmem_to_page(data);
> > unsigned int off = offset_in_page(data);
> > size_t len = min_t(size_t, count, PAGE_SIZE - off);
> >
> > - WARN_ON_ONCE(bio_add_page(bio, page, len, off) != len);
> > + if (bio_add_page(bio, page, len, off) != len) {
> > + xfs_force_shutdown(mp, SHUTDOWN_LOG_IO_ERROR);
> > + break;
> > + }
> >
> > data += len;
> > count -= len;
> > @@ -1762,7 +1768,7 @@ xlog_write_iclog(
> > if (need_flush)
> > iclog->ic_bio.bi_opf |= REQ_PREFLUSH;
> >
> > - xlog_map_iclog_data(&iclog->ic_bio, iclog->ic_data, count);
> > + xlog_map_iclog_data(iclog, count);
>
> Can you just return an error from xlog_map_iclog_data and shut down
> in the caller? Besides keeping the abstraction levels similar I had
> also hoped to lift xlog_map_iclog_data into the block layer eventually.
>

Sure. That's probably more appropriate now that I look again because it
looks like we still submit the current bio with this patch. Something
like the following..?

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 2a90a483c2d6..92a58a6bc32b 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -1703,7 +1703,7 @@ xlog_bio_end_io(
&iclog->ic_end_io_work);
}

-static void
+static int
xlog_map_iclog_data(
struct bio *bio,
void *data,
@@ -1714,11 +1714,14 @@ xlog_map_iclog_data(
unsigned int off = offset_in_page(data);
size_t len = min_t(size_t, count, PAGE_SIZE - off);

- WARN_ON_ONCE(bio_add_page(bio, page, len, off) != len);
+ if (bio_add_page(bio, page, len, off) != len)
+ break;

data += len;
count -= len;
} while (count);
+
+ return count;
}

STATIC void
@@ -1762,7 +1765,10 @@ xlog_write_iclog(
if (need_flush)
iclog->ic_bio.bi_opf |= REQ_PREFLUSH;

- xlog_map_iclog_data(&iclog->ic_bio, iclog->ic_data, count);
+ if (xlog_map_iclog_data(&iclog->ic_bio, iclog->ic_data, count)) {
+ xfs_force_shutdown(log->l_mp, SHUTDOWN_LOG_IO_ERROR);
+ return;
+ }
if (is_vmalloc_addr(iclog->ic_data))
flush_kernel_vmap_range(iclog->ic_data, count);