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btrfs: fix and document the zoned device choice in alloc_new_bio

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Zone Append bios only need a valid block device in struct bio, but
not the device in the btrfs_bio.  Use the information from
btrfs_zoned_get_device to set up bi_bdev and fix zoned writes on
multi-device file system with non-homogeneous capabilities and remove
the pointless btrfs_bio.device assignment.

Add big fat comments explaining what is going on here.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Christoph Hellwig 2022-03-24 17:52:10 +01:00 committed by David Sterba
parent 50ff57888d
commit 50f1cff3d8
1 changed files with 27 additions and 14 deletions
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41
fs/btrfs/extent_io.c
View file

@ -3334,24 +3334,37 @@ static int alloc_new_bio(struct btrfs_inode *inode,
ret = calc_bio_boundaries(bio_ctrl, inode, file_offset);
if (ret < 0)
goto error;
if (wbc) {
struct block_device *bdev;
/*
* For Zone append we need the correct block_device that we are
* going to write to set in the bio to be able to respect the
* hardware limitation. Look it up here:
*/
if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
struct btrfs_device *dev;
bdev = fs_info->fs_devices->latest_dev->bdev;
bio_set_dev(bio, bdev);
wbc_init_bio(wbc, bio);
}
if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
struct btrfs_device *device;
dev = btrfs_zoned_get_device(fs_info, disk_bytenr,
fs_info->sectorsize);
if (IS_ERR(dev)) {
ret = PTR_ERR(dev);
goto error;
}
device = btrfs_zoned_get_device(fs_info, disk_bytenr,
fs_info->sectorsize);
if (IS_ERR(device)) {
ret = PTR_ERR(device);
goto error;
bio_set_dev(bio, dev->bdev);
} else {
/*
* Otherwise pick the last added device to support
* cgroup writeback. For multi-device file systems this
* means blk-cgroup policies have to always be set on the
* last added/replaced device. This is a bit odd but has
* been like that for a long time.
*/
bio_set_dev(bio, fs_info->fs_devices->latest_dev->bdev);
}
btrfs_bio(bio)->device = device;
wbc_init_bio(wbc, bio);
} else {
ASSERT(bio_op(bio) != REQ_OP_ZONE_APPEND);
}
return 0;
error: