The patch titled
Subject: mm-make-snapshotting-pages-for-stable-writes-a-per-bio-operation-v3
has been added to the -mm tree. Its filename is
mm-make-snapshotting-pages-for-stable-writes-a-per-bio-operation-v3.patch
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------------------------------------------------------
From: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>
Subject: mm-make-snapshotting-pages-for-stable-writes-a-per-bio-operation-v3
v3: Improve the documentation in jbd for why we're doing this, and clean up
some code.
[darrick.wong@xxxxxxxxxx: Fold in a couple of small cleanups from akpm]
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Artem Bityutskiy <dedekind1@xxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/buffer.c | 2 +-
fs/jbd/commit.c | 21 ++++++++++++++++++++-
include/linux/blk_types.h | 1 +
3 files changed, 22 insertions(+), 2 deletions(-)
diff -puN fs/buffer.c~mm-make-snapshotting-pages-for-stable-writes-a-per-bio-operation-v3 fs/buffer.c
--- a/fs/buffer.c~mm-make-snapshotting-pages-for-stable-writes-a-per-bio-operation-v3
+++ a/fs/buffer.c
@@ -2999,7 +2999,7 @@ int _submit_bh(int rw, struct buffer_hea
}
EXPORT_SYMBOL_GPL(_submit_bh);
-int submit_bh(int rw, struct buffer_head * bh)
+int submit_bh(int rw, struct buffer_head *bh)
{
return _submit_bh(rw, bh, 0);
}
diff -puN fs/jbd/commit.c~mm-make-snapshotting-pages-for-stable-writes-a-per-bio-operation-v3 fs/jbd/commit.c
--- a/fs/jbd/commit.c~mm-make-snapshotting-pages-for-stable-writes-a-per-bio-operation-v3
+++ a/fs/jbd/commit.c
@@ -162,7 +162,16 @@ static void journal_do_submit_data(struc
for (i = 0; i < bufs; i++) {
wbuf[i]->b_end_io = end_buffer_write_sync;
- /* We use-up our safety reference in submit_bh() */
+ /*
+ * Here we write back pagecache data that may be mmaped. Since
+ * we cannot afford to clean the page and set PageWriteback
+ * here due to lock ordering (page lock ranks above transaction
+ * start), the data can change while IO is in flight. Tell the
+ * block layer it should bounce the bio pages if stable data
+ * during write is required.
+ *
+ * We use up our safety reference in submit_bh().
+ */
_submit_bh(write_op, wbuf[i], 1 << BIO_SNAP_STABLE);
}
}
@@ -667,6 +676,16 @@ start_journal_io:
clear_buffer_dirty(bh);
set_buffer_uptodate(bh);
bh->b_end_io = journal_end_buffer_io_sync;
+ /*
+ * In data=journal mode, here we can end up
+ * writing pagecache data that might be
+ * mmapped. Since we can't afford to clean the
+ * page and set PageWriteback (see the comment
+ * near the other use of _submit_bh()), the
+ * data can change while the write is in
+ * flight. Tell the block layer to bounce the
+ * bio pages if stable pages are required.
+ */
_submit_bh(write_op, bh, 1 << BIO_SNAP_STABLE);
}
cond_resched();
diff -puN include/linux/blk_types.h~mm-make-snapshotting-pages-for-stable-writes-a-per-bio-operation-v3 include/linux/blk_types.h
--- a/include/linux/blk_types.h~mm-make-snapshotting-pages-for-stable-writes-a-per-bio-operation-v3
+++ a/include/linux/blk_types.h
@@ -112,6 +112,7 @@ struct bio {
#define BIO_QUIET 10 /* Make BIO Quiet */
#define BIO_MAPPED_INTEGRITY 11/* integrity metadata has been remapped */
#define BIO_SNAP_STABLE 12 /* bio data must be snapshotted during write */
+
/*
* Flags starting here get preserved by bio_reset() - this includes
* BIO_POOL_IDX()
_
Patches currently in -mm which might be from darrick.wong@xxxxxxxxxx are
linux-next.patch
mm-make-snapshotting-pages-for-stable-writes-a-per-bio-operation.patch
mm-make-snapshotting-pages-for-stable-writes-a-per-bio-operation-v3.patch
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