From 8530c37a70df71ea8a04fbafabba0b92f4475c6c Mon Sep 17 00:00:00 2001
From: David Sterba <dsterba@suse.com>
Date: Fri, 30 Aug 2019 15:42:07 +0200
Subject: [PATCH] btrfs: get bdev from latest_dev for dio bh_result
To remove use of extent_map::bdev we need to find a replacement, and the
latest_bdev is the only one we can use here, because inode::i_bdev and
superblock::s_bdev are NULL.
The DIO code uses bdev in two places:
* to read blocksize to perform alignment checks in
do_blockdev_direct_IO, but we do them in btrfs code before any call to
DIO
* in the following call chain:
do_direct_IO
get_more_blocks
sdio->get_block() <-- this is btrfs_get_blocks_direct
subsequently the map_bh->b_dev member is used in clean_bdev_aliases
and dio_new_bio to set the bio's bdev to that of the buffer_head.
However, because we have provided a submit function dio_bio_submit
calls our submission function and ignores the bdev.
So it's safe to pass any valid bdev that's used within the filesystem.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
fs/btrfs/inode.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index b943c9770533ab..5edc6a27ea4ae9 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7662,6 +7662,8 @@ static int btrfs_get_blocks_direct_read(struct extent_map *em,
struct inode *inode,
u64 start, u64 len)
{
+ struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+
if (em->block_start == EXTENT_MAP_HOLE ||
test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
return -ENOENT;
@@ -7671,7 +7673,7 @@ static int btrfs_get_blocks_direct_read(struct extent_map *em,
bh_result->b_blocknr = (em->block_start + (start - em->start)) >>
inode->i_blkbits;
bh_result->b_size = len;
- bh_result->b_bdev = em->bdev;
+ bh_result->b_bdev = fs_info->fs_devices->latest_bdev;
set_buffer_mapped(bh_result);
return 0;
@@ -7754,7 +7756,7 @@ skip_cow:
bh_result->b_blocknr = (em->block_start + (start - em->start)) >>
inode->i_blkbits;
bh_result->b_size = len;
- bh_result->b_bdev = em->bdev;
+ bh_result->b_bdev = fs_info->fs_devices->latest_bdev;
set_buffer_mapped(bh_result);
if (!test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
--
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