On 11/09/2012 03:36 PM, Dave Chinner wrote: > On Fri, Nov 09, 2012 at 02:47:41PM +0800, Jeff Liu wrote: >> Hello, >> >> I observed that there is an issue on our official DOC for AG disk >> layout, which can be found at: >> http://xfs.org/docs/xfsdocs-xml-dev/XFS_Filesystem_Structure//tmp/en-US/html/Allocation_Groups.html >> >> It shows that the IBT block is followed by the block where AGFL sector >> resides. However, it should be followed by the >> CNT block according to my debug, like below: >> >> ------------------------------- >> superblock >> AG free block info >> AG inode B+tree info >> AG internal free list >> ------------------------------- >> Root of free space B+tree >> B+tree key is block number >> ------------------------------- >> Root of free space B+tree >> B+tree key is block count >> -------------------------------- >> Root of inodes B+tree >> -------------------------------- >> >> Maybe the DOC is old, or am I missing anything? If not, can we correct it? > > The btree root blocks are dynamic. mkfs.xfs puts them in a fixed > place, just like growfs does, but the moment you split a root block, > it moves from that location. Hence the only way to reliably find the > root btree block is to look up the point in the AGF/AGI, and that's > what the document shows. IOWs, the ordering in the document is not > important - the linkage is - as the root blocks can end up > *anywhere* in the AG. > > e.g: > > $ sudo xfs_db -r -c "agf 0" -c p /dev/vda > magicnum = 0x58414746 > versionnum = 1 > seqno = 0 > length = 262144 > bnoroot = 596 > cntroot = 1003 > bnolevel = 2 > cntlevel = 2 > .... Ah, thanks for your quick response, now I understood. :) Regards, -Jeff _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
