btrfs: get bdev directly from fs_devices in submit_extent_page
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Message ID 20191118223615.12236-1-dsterba@suse.com
State New
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Series
  • btrfs: get bdev directly from fs_devices in submit_extent_page
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Commit Message

David Sterba Nov. 18, 2019, 10:36 p.m. UTC
This is preparatory patch to remove @bdev parameter from
submit_extent_page. It can't be removed completely, because the cgroups
need it for wbc when initializing the bio

wbc_init_bio
  bio_associate_blkg_from_css
    dereference bdev->bi_disk->queue

The bdev pointer is the same as latest_bdev, thus no functional change.
We can retrieve it from fs_devices that's reachable through several
dereferences. The local variable shadows the parameter, but that's only
temporary.

Signed-off-by: David Sterba <dsterba@suse.com>
---

This is a prerequisite for patchset to avoid crash when cgroups are
enabled

https://lore.kernel.org/linux-btrfs/cover.1570474492.git.dsterba@suse.com/

 fs/btrfs/extent_io.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Patch
diff mbox series

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index ceb3c028894e..9a2339a54a9d 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2987,13 +2987,16 @@  static int submit_extent_page(unsigned int opf, struct extent_io_tree *tree,
 	}
 
 	bio = btrfs_bio_alloc(offset);
-	bio_set_dev(bio, bdev);
 	bio_add_page(bio, page, page_size, pg_offset);
 	bio->bi_end_io = end_io_func;
 	bio->bi_private = tree;
 	bio->bi_write_hint = page->mapping->host->i_write_hint;
 	bio->bi_opf = opf;
 	if (wbc) {
+		struct block_device *bdev;
+
+		bdev = BTRFS_I(page->mapping->host)->root->fs_info->fs_devices->latest_bdev;
+		bio_set_dev(bio, bdev);
 		wbc_init_bio(wbc, bio);
 		wbc_account_cgroup_owner(wbc, page, page_size);
 	}