> On 11 May 2019, at 11:24 PM, Steven Davies <btrfs-list@xxxxxxxxxxx> wrote: > > Tested-by: Steven Davies <btrfs-list@xxxxxxxxxxx> > > Series (inc. btrfs-progs changes) tested working as expected against current btrfs-devel and btrfs-progs/devel. > > Am I correct in thinking that if more than one devid is assigned as a readmirror, the lowest available devid will be preferred? > As of now, it's just don’t do that kind of approach and it picks stripe 0 as read mirror device. And a disk is stripe 0 if it has largest disk free space as the time of chunk allocation. So it's kind of hard to predict which disk gets picked. I have plans to write a patch to maintain the consistent allocation order. > Also I think it would be nice to be able to set this property at mkfs time. > Yeah. It certainly makes sense in case of mixed device types such as ssd and hdd or hdd/ssd and iscsi. Thanks, Anand > I'd love to see this feature make it upstream. > > -- > Steven Davies > > On 25/04/2019 12:59, Anand Jain wrote: >> These patches are tested to be working fine. >> Function call chain __btrfs_map_block()->find_live_mirror() uses >> thread pid to determine the %mirror_num when the mirror_num=0. >> This patch introduces a framework so that we can add policies to determine >> the %mirror_num. And adds the devid as the readmirror policy. >> The property is stored as an extented attributes of root inode >> (BTRFS_FS_TREE_OBJECTID). >> User provided devid list is validated against the fs_devices::dev_list. >> For example: >> Usage: >> btrfs property set <mnt> readmirror devid<n>[,<m>...] >> btrfs property set <mnt> readmirror "" >> mkfs.btrfs -fq -draid1 -mraid1 /dev/sd[b-d] && mount /dev/sdb /btrfs >> btrfs prop set /btrfs readmirror devid1,2 >> btrfs prop get /btrfs readmirror >> readmirror=devid1,2 >> getfattr -n btrfs.readmirror --absolute-names /btrfs >> btrfs.readmirror="devid1,2" >> btrfs prop set /btrfs readmirror "" >> getfattr -n btrfs.readmirror --absolute-names /btrfs >> /btrfs: btrfs.readmirror: No such attribute >> btrfs prop get /btrfs readmirror >> RFC->v1: >> Drops pid as one of the readmirror policy choices and as usual remains >> as default. And when the devid is reset the readmirror policy falls back >> to pid. >> Drops the mount -o readmirror idea, it can be added at a later point of >> time. >> Property now accepts more than 1 devid as readmirror device. As shown >> in the example above. >> Anand Jain (3): >> btrfs: add inode pointer to prop_handler::validate() >> btrfs: add readmirror property framework >> btrfs: add readmirror devid property >> fs/btrfs/props.c | 120 +++++++++++++++++++++++++++++++++++++++++++-- >> fs/btrfs/props.h | 4 +- >> fs/btrfs/volumes.c | 25 +++++++++- >> fs/btrfs/volumes.h | 8 +++ >> fs/btrfs/xattr.c | 2 +- >> 5 files changed, 150 insertions(+), 9 deletions(-) >> Anand Jain (2): >> btrfs-progs: add helper to create xattr name >> btrfs-progs: add readmirror policy >> props.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------ >> 1 file changed, 68 insertions(+), 7 deletions(-)
