On Sunday, February 23, 2020 3:21 PM Amir Goldstein wrote: > On Sun, Feb 23, 2020 at 9:28 AM Chandan Rajendra > <chandanrlinux@xxxxxxxxx> wrote: > > > > Log space reservation for xattr insert operation can be divided into two > > parts, > > 1. Mount time > > - Inode > > - Superblock for accounting space allocations > > - AGF for accounting space used by count, block number, rmap and refcnt > > btrees. > > > > 2. The remaining log space can only be calculated at run time because, > > - A local xattr can be large enough to cause a double split of the dabtree. > > - The value of the xattr can be large enough to be stored in remote > > blocks. The contents of the remote blocks are not logged. > > > > The log space reservation could be, > > - 2 * XFS_DA_NODE_MAXDEPTH number of blocks. Additional XFS_DA_NODE_MAXDEPTH > > number of blocks are required if xattr is large enough to cause another > > split of the dabtree path from root to leaf block. > > - BMBT blocks for storing (2 * XFS_DA_NODE_MAXDEPTH) record > > entries. Additional XFS_DA_NODE_MAXDEPTH number of blocks are required in > > case of a double split of the dabtree path from root to leaf blocks. > > - Space for logging blocks of count, block number, rmap and refcnt btrees. > > > > Presently, mount time log reservation includes block count required for a > > single split of the dabtree. The dabtree block count is also taken into > > account by xfs_attr_calc_size(). > > > > Also, AGF log space reservation isn't accounted for. > > > > Due to the reasons mentioned above, log reservation calculation for xattr > > insert operation gives an incorrect value. > > > > Apart from the above, xfs_log_calc_max_attrsetm_res() passes byte count as > > an argument to XFS_NEXTENTADD_SPACE_RES() instead of block count. > > > > To fix these issues, this commit changes xfs_attr_calc_size() to also > > calculate the number of dabtree blocks that need to be logged. > > > > xfs_attr_set() uses the following values computed by xfs_attr_calc_size() > > 1. The number of dabtree blocks that need to be logged. > > 2. The number of remote blocks that need to be allocated. > > 3. The number of dabtree blocks that need to be allocated. > > 4. The number of bmbt blocks that need to be allocated. > > 5. The total number of blocks that need to be allocated. > > > > ... to compute number of bytes that need to be reserved in the log. > > > > This commit also modifies xfs_log_calc_max_attrsetm_res() to invoke > > xfs_attr_calc_size() to obtain the number of blocks to be logged which it uses > > to figure out the total number of bytes to be logged. > > > > Signed-off-by: Chandan Rajendra <chandanrlinux@xxxxxxxxx> > > Hi Chandan, > Hi Amir, > It would have been useful to get this sort of overview in a cover > letter instead of > having to find it in the last patch. > Sure, I will re-send the patchset with a cover letter. > I suppose it is a coincident that this work ended up in our mailboxes together > with Allison's delayed attr work, but it is interesting to know if the two works > affect each other in any way. My patchset fixes bugs in the calculation of log space reservation for "xattr set" operation. I read the code at "https://github.com/allisonhenderson/xfs_work.git delay_ready_attrs_v7" and found that the bugs still exist in that code as well. So IMHO, the two patchsets do not mutually exclude each other. -- chandan
