[BUG]
There is a report that, for zoned devices btrfstune is unable to convert
it to block group tree.
# btrfstune /dev/nullb0 --convert-to-block-group-tree
Error reading 1342193664, -1
Error reading 1342193664, -1
ERROR: cannot read chunk root
ERROR: open ctree failed
[CAUSE]
For read-write opened zoned devices, all the read/write has to be
aligned to its sector size.
However btrfs stores its metadata by extent_buffer::data[], which has
all the structures before it, thus never aligned to zoned device sector
size.
Normally we would require btrfs_pread() and btrfs_pwrite() to do the
extra alignment, but during open_ctree(), we are not aware if a device
is zoned or not.
Thus we rely on if the fd is opened with O_DIRECT flag, if the fd has
O_DIRECT, then we would temporarily set fs_info->zoned for chunk tree
read.
Unforunately not all open_ctree_fd() callers have the flags set
properly, and btrfstune is one of the missing call site.
This makes all the read not properly aligned and cause read failure.
[FIX]
Just manually check if the target device is a zoned one, and set
O_DIRECT accordingly.
Issue: #765
Pull-request: #767
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
738bb7f0f0