btrfs: drop bio_set_dev where not needed

bio_set_dev sets a bdev to a bio and is not only setting a pointer bug
also changing some state bits if there was a different bdev set before.
This is one thing that's not needed.

Another thing is that setting a bdev at bio allocation time is too early
and actually does not work with plain redundancy profiles, where each
time we submit a bio to a device, the bdev is set correctly.

In many places the bio bdev is set to latest_bdev that seems to serve as
a stub pointer "just to put something to bio". But we don't have to do
that.

Where do we know which bdev to set:

* for regular IO: submit_stripe_bio that's called by btrfs_map_bio

* repair IO: repair_io_failure, read or write from specific device

* super block write (using buffer_heads but uses raw bdev) and barriers

* scrub: this does not use all regular IO paths as it needs to reach all
  copies, verify and fixup eventually, and for that all bdev management
  is independent

* raid56: rbio_add_io_page, for the RMW write

* integrity-checker: does it's own low-level block tracking

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

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 53aee0d..ee834ef 100644 (file)
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -422,7 +422,6 @@ blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start,
        int pg_index = 0;
        struct page *page;
        u64 first_byte = disk_start;
-       struct block_device *bdev;
        blk_status_t ret;
        int skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;
 
@@ -441,10 +440,7 @@ blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start,
        cb->orig_bio = NULL;
        cb->nr_pages = nr_pages;
 
-       bdev = fs_info->fs_devices->latest_bdev;
-
        bio = btrfs_bio_alloc(first_byte);
-       bio_set_dev(bio, bdev);
        bio->bi_opf = REQ_OP_WRITE | write_flags;
        bio->bi_private = cb;
        bio->bi_end_io = end_compressed_bio_write;
@@ -492,7 +488,6 @@ blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start,
                        }
 
                        bio = btrfs_bio_alloc(first_byte);
-                       bio_set_dev(bio, bdev);
                        bio->bi_opf = REQ_OP_WRITE | write_flags;
                        bio->bi_private = cb;
                        bio->bi_end_io = end_compressed_bio_write;
@@ -660,7 +655,6 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
        unsigned long nr_pages;
        unsigned long pg_index;
        struct page *page;
-       struct block_device *bdev;
        struct bio *comp_bio;
        u64 cur_disk_byte = (u64)bio->bi_iter.bi_sector << 9;
        u64 em_len;
@@ -711,8 +705,6 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
        if (!cb->compressed_pages)
                goto fail1;
 
-       bdev = fs_info->fs_devices->latest_bdev;
-
        for (pg_index = 0; pg_index < nr_pages; pg_index++) {
                cb->compressed_pages[pg_index] = alloc_page(GFP_NOFS |
                                                              __GFP_HIGHMEM);
@@ -731,7 +723,6 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
        cb->len = bio->bi_iter.bi_size;
 
        comp_bio = btrfs_bio_alloc(cur_disk_byte);
-       bio_set_dev(comp_bio, bdev);
        comp_bio->bi_opf = REQ_OP_READ;
        comp_bio->bi_private = cb;
        comp_bio->bi_end_io = end_compressed_bio_read;
@@ -782,7 +773,6 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
                        }
 
                        comp_bio = btrfs_bio_alloc(cur_disk_byte);
-                       bio_set_dev(comp_bio, bdev);
                        comp_bio->bi_opf = REQ_OP_READ;
                        comp_bio->bi_private = cb;
                        comp_bio->bi_end_io = end_compressed_bio_read;

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 9a2339a..c4fcfd7 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2544,7 +2544,6 @@ struct bio *btrfs_create_repair_bio(struct inode *inode, struct bio *failed_bio,
        bio = btrfs_io_bio_alloc(1);
        bio->bi_end_io = endio_func;
        bio->bi_iter.bi_sector = failrec->logical >> 9;
-       bio_set_dev(bio, fs_info->fs_devices->latest_bdev);
        bio->bi_iter.bi_size = 0;
        bio->bi_private = data;