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authorDarrick J. Wong <darrick.wong@oracle.com>2013-04-29 15:07:25 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-04-29 15:54:33 -0700
commit7136851117744f1d291bed6d307432699d405109 (patch)
tree6dc7d6bef45e24ad0d3d5d1b9290a81109758172
parentmm/hugetlb: add more arch-defined huge_pte functions (diff)
downloadlinux-dev-7136851117744f1d291bed6d307432699d405109.tar.xz
linux-dev-7136851117744f1d291bed6d307432699d405109.zip
mm: make snapshotting pages for stable writes a per-bio operation
Walking a bio's page mappings has proved problematic, so create a new bio flag to indicate that a bio's data needs to be snapshotted in order to guarantee stable pages during writeback. Next, for the one user (ext3/jbd) of snapshotting, hook all the places where writes can be initiated without PG_writeback set, and set BIO_SNAP_STABLE there. We must also flag journal "metadata" bios for stable writeout, since file data can be written through the journal. Finally, the MS_SNAP_STABLE mount flag (only used by ext3) is now superfluous, so get rid of it. [akpm@linux-foundation.org: rename _submit_bh()'s `flags' to `bio_flags', delobotomize the _submit_bh declaration] [akpm@linux-foundation.org: teeny cleanup] Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Artem Bityutskiy <dedekind1@gmail.com> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/buffer.c9
-rw-r--r--fs/ext3/super.c1
-rw-r--r--fs/jbd/commit.c25
-rw-r--r--include/linux/blk_types.h3
-rw-r--r--include/linux/buffer_head.h1
-rw-r--r--include/uapi/linux/fs.h1
-rw-r--r--mm/bounce.c21
-rw-r--r--mm/page-writeback.c4
8 files changed, 34 insertions, 31 deletions
diff --git a/fs/buffer.c b/fs/buffer.c
index b4dcb34c9635..71578d69b82d 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2949,7 +2949,7 @@ static void guard_bh_eod(int rw, struct bio *bio, struct buffer_head *bh)
}
}
-int submit_bh(int rw, struct buffer_head * bh)
+int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags)
{
struct bio *bio;
int ret = 0;
@@ -2984,6 +2984,7 @@ int submit_bh(int rw, struct buffer_head * bh)
bio->bi_end_io = end_bio_bh_io_sync;
bio->bi_private = bh;
+ bio->bi_flags |= bio_flags;
/* Take care of bh's that straddle the end of the device */
guard_bh_eod(rw, bio, bh);
@@ -2997,6 +2998,12 @@ int submit_bh(int rw, struct buffer_head * bh)
bio_put(bio);
return ret;
}
+EXPORT_SYMBOL_GPL(_submit_bh);
+
+int submit_bh(int rw, struct buffer_head *bh)
+{
+ return _submit_bh(rw, bh, 0);
+}
EXPORT_SYMBOL(submit_bh);
/**
diff --git a/fs/ext3/super.c b/fs/ext3/super.c
index fb5120a5505c..3dc48cc8b6eb 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -2067,7 +2067,6 @@ static int ext3_fill_super (struct super_block *sb, void *data, int silent)
test_opt(sb,DATA_FLAGS) == EXT3_MOUNT_JOURNAL_DATA ? "journal":
test_opt(sb,DATA_FLAGS) == EXT3_MOUNT_ORDERED_DATA ? "ordered":
"writeback");
- sb->s_flags |= MS_SNAP_STABLE;
return 0;
diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
index 86b39b167c23..11bb11f48b3a 100644
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -162,8 +162,17 @@ static void journal_do_submit_data(struct buffer_head **wbuf, int bufs,
for (i = 0; i < bufs; i++) {
wbuf[i]->b_end_io = end_buffer_write_sync;
- /* We use-up our safety reference in submit_bh() */
- submit_bh(write_op, wbuf[i]);
+ /*
+ * 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);
}
}
@@ -667,7 +676,17 @@ start_journal_io:
clear_buffer_dirty(bh);
set_buffer_uptodate(bh);
bh->b_end_io = journal_end_buffer_io_sync;
- submit_bh(write_op, bh);
+ /*
+ * 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 --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index cdf11191e645..22990cf4439d 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -111,12 +111,13 @@ struct bio {
#define BIO_FS_INTEGRITY 9 /* fs owns integrity data, not block layer */
#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()
*/
-#define BIO_RESET_BITS 12
+#define BIO_RESET_BITS 13
#define bio_flagged(bio, flag) ((bio)->bi_flags & (1 << (flag)))
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 5afc4f94d110..4c16c4a88d47 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -181,6 +181,7 @@ void ll_rw_block(int, int, struct buffer_head * bh[]);
int sync_dirty_buffer(struct buffer_head *bh);
int __sync_dirty_buffer(struct buffer_head *bh, int rw);
void write_dirty_buffer(struct buffer_head *bh, int rw);
+int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags);
int submit_bh(int, struct buffer_head *);
void write_boundary_block(struct block_device *bdev,
sector_t bblock, unsigned blocksize);
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index c7fc1e6517c3..a4ed56cf0eac 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -88,7 +88,6 @@ struct inodes_stat_t {
#define MS_STRICTATIME (1<<24) /* Always perform atime updates */
/* These sb flags are internal to the kernel */
-#define MS_SNAP_STABLE (1<<27) /* Snapshot pages during writeback, if needed */
#define MS_NOSEC (1<<28)
#define MS_BORN (1<<29)
#define MS_ACTIVE (1<<30)
diff --git a/mm/bounce.c b/mm/bounce.c
index 5f8901768602..a5c2ec3589cb 100644
--- a/mm/bounce.c
+++ b/mm/bounce.c
@@ -181,32 +181,13 @@ static void bounce_end_io_read_isa(struct bio *bio, int err)
#ifdef CONFIG_NEED_BOUNCE_POOL
static int must_snapshot_stable_pages(struct request_queue *q, struct bio *bio)
{
- struct page *page;
- struct backing_dev_info *bdi;
- struct address_space *mapping;
- struct bio_vec *from;
- int i;
-
if (bio_data_dir(bio) != WRITE)
return 0;
if (!bdi_cap_stable_pages_required(&q->backing_dev_info))
return 0;
- /*
- * Based on the first page that has a valid mapping, decide whether or
- * not we have to employ bounce buffering to guarantee stable pages.
- */
- bio_for_each_segment(from, bio, i) {
- page = from->bv_page;
- mapping = page_mapping(page);
- if (!mapping)
- continue;
- bdi = mapping->backing_dev_info;
- return mapping->host->i_sb->s_flags & MS_SNAP_STABLE;
- }
-
- return 0;
+ return test_bit(BIO_SNAP_STABLE, &bio->bi_flags);
}
#else
static int must_snapshot_stable_pages(struct request_queue *q, struct bio *bio)
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index efe68148f621..4514ad7415c3 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2311,10 +2311,6 @@ void wait_for_stable_page(struct page *page)
if (!bdi_cap_stable_pages_required(bdi))
return;
-#ifdef CONFIG_NEED_BOUNCE_POOL
- if (mapping->host->i_sb->s_flags & MS_SNAP_STABLE)
- return;
-#endif /* CONFIG_NEED_BOUNCE_POOL */
wait_on_page_writeback(page);
}