Re: [PATCH V2 2/2] xfs: Fix log reservation calculation for xattr insert operation

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On Friday, January 17, 2020 10:16 AM Chandan Rajendra wrote: 
> On Friday, January 17, 2020 6:16 AM Darrick J. Wong wrote: 
> > On Wed, Jan 15, 2020 at 06:24:21PM +0530, Chandan Rajendra 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 be count, block number, rmapbt 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. Hence log reservation
> > > calculation for xattr insert operation gives incorrect value.
> > > 
> > > Apart from the above, xfs_log_calc_max_attrsetm_res() passes a byte count as
> > > an argument to XFS_NEXTENTADD_SPACE_RES() instead of block count.
> > > 
> > > To fix these issues, this commit refactors xfs_attr_calc_size() to calculate,
> > > 1. The number of dabtree blocks that need to be logged.
> > > 2. The number of remote blocks that need to allocated.
> > > 3. The number of dabtree blocks that need to allocated.
> > > 
> > > xfs_attr_set() uses this information to compute
> > > 1. Number of blocks that needs to allocated during the transaction.
> > > 2. Number of bytes that needs 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 dabtree blocks to be
> > > logged which it uses to figure out the total number of blocks to be logged.
> > > 
> > > Signed-off-by: Chandan Rajendra <chandanrlinux@xxxxxxxxx>
> > > ---
> > > Changelog:
> > > V1 -> V2:
> > > 1. xfs_attr_calc_size() computes
> > >    - Number of blocks required to log dabtree blocks.
> > >    - Number of remote blocks.
> > >    - Total dabtree blocks to be allocated.
> > > 2. Add new function xfs_calc_attr_blocks() to compute the total number of
> > >    blocks to be allocated during xattr insert operation.
> > > 3. Add new function xfs_calc_attr_res() to compute the log space to be
> > >    reserved during xattr insert operation.
> > > 
> > >  fs/xfs/libxfs/xfs_attr.c       | 108 +++++++++++++++++++++------------
> > >  fs/xfs/libxfs/xfs_attr.h       |   3 +
> > >  fs/xfs/libxfs/xfs_log_rlimit.c |  17 +++---
> > >  fs/xfs/libxfs/xfs_trans_resv.c |  56 +++++++++--------
> > >  fs/xfs/libxfs/xfs_trans_resv.h |   2 +
> > >  5 files changed, 113 insertions(+), 73 deletions(-)
> > > 
> > > diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> > > index 1eae1db74f6c..363b4c47b134 100644
> > > --- a/fs/xfs/libxfs/xfs_attr.c
> > > +++ b/fs/xfs/libxfs/xfs_attr.c
> > > @@ -183,43 +183,6 @@ xfs_attr_get(
> > >  	return 0;
> > >  }
> > >  
> > > -/*
> > > - * Calculate how many blocks we need for the new attribute,
> > > - */
> > > -STATIC int
> > > -xfs_attr_calc_size(
> > > -	struct xfs_da_args	*args,
> > > -	int			*local)
> > > -{
> > > -	struct xfs_mount	*mp = args->dp->i_mount;
> > > -	int			size;
> > > -	int			nblks;
> > > -
> > > -	/*
> > > -	 * Determine space new attribute will use, and if it would be
> > > -	 * "local" or "remote" (note: local != inline).
> > > -	 */
> > > -	size = xfs_attr_leaf_newentsize(mp, args->namelen, args->valuelen,
> > > -					local);
> > > -	nblks = XFS_DAENTER_SPACE_RES(mp, XFS_ATTR_FORK);
> > > -	if (*local) {
> > > -		if (size > (args->geo->blksize / 2)) {
> > > -			/* Double split possible */
> > > -			nblks *= 2;
> > > -		}
> > > -	} else {
> > > -		/*
> > > -		 * Out of line attribute, cannot double split, but
> > > -		 * make room for the attribute value itself.
> > > -		 */
> > > -		uint	dblocks = xfs_attr3_rmt_blocks(mp, args->valuelen);
> > > -		nblks += dblocks;
> > > -		nblks += XFS_NEXTENTADD_SPACE_RES(mp, dblocks, XFS_ATTR_FORK);
> > > -	}
> > > -
> > > -	return nblks;
> > > -}
> > > -
> > >  STATIC int
> > >  xfs_attr_try_sf_addname(
> > >  	struct xfs_inode	*dp,
> > > @@ -248,6 +211,64 @@ xfs_attr_try_sf_addname(
> > >  	return error ? error : error2;
> > >  }
> > >  
> > > +STATIC uint
> > > +xfs_calc_attr_blocks(
> > > +	struct xfs_mount	*mp,
> > > +	unsigned int		total_dablks,
> > > +	unsigned int		rmt_blks)
> > > +{
> > > +	unsigned int bmbt_blks;
> > > +
> > > +	bmbt_blks = XFS_NEXTENTADD_SPACE_RES(mp, total_dablks + rmt_blks,
> > > +					XFS_ATTR_FORK);
> > > +	return total_dablks + rmt_blks + bmbt_blks;
> > 
> > I think this calculation could be added to xfs_attr_calc_size and passed
> > back to the caller as another outparam.
> > 
> > At this point we have five different block counts I'm wondering if we
> > should create a struct and pass it around...
> > 
> > > +}
> > > +
> > > +/*
> > > + * Calculate how many blocks we need for the new attribute,
> > > + */
> > > +void
> > > +xfs_attr_calc_size(
> > > +	struct xfs_mount	*mp,
> > > +	int			namelen,
> > > +	int			valuelen,
> > > +	int			*local,
> > > +	unsigned int		*log_dablks,
> > > +	unsigned int		*rmt_blks,
> > > +	unsigned int		*total_dablks)
> > 
> > ...something like this?  It'll be much easier to remember what each of
> > those parameters actually do with a full sentence comment:
> > 
> > struct xfs_attr_set_resv {
> > 	/* Number of blocks in the da btree that we might need to log. */
> > 	unsigned int		log_dablks;
> > 
> > 	/* Number of unlogged blocks needed to store the remote attr value. */
> > 	unsigned int		rmt_blks;
> > 
> > 	/* Blocks we might need to map into the attribute fork. */
> > 	unsigned int		total_dablks;
> > 
> > 	/* Blocks we might need to allocate. */
> > 	unsigned int		alloc_blks;
> > 
> > 	/* Blocks we might need to create all the new attr fork mappings. */
> > 	unsigned int		bmbt_blks;
> > };
> > 
> > > +{
> > > +	unsigned int		blksize;
> > > +	int			size;
> > > +
> > > +	blksize = mp->m_dir_geo->blksize;
> > > +	*log_dablks = 0;
> > > +	*rmt_blks = 0;
> > > +	*total_dablks = 0;
> > 
> > No need to zero out variables that we're going to set two lines later.
> > 
> > > +
> > > +	/*
> > > +	 * Determine space new attribute will use, and if it would be
> > > +	 * "local" or "remote" (note: local != inline).
> > > +	 */
> > > +	size = xfs_attr_leaf_newentsize(mp, namelen, valuelen, local);
> > > +
> > > +	*total_dablks = XFS_DAENTER_BLOCKS(mp, XFS_ATTR_FORK);
> > > +	*log_dablks = 2 * *total_dablks;
> > > +
> > > +	if (*local) {
> > > +		if (size > (blksize / 2)) {
> > > +			/* Double split possible */
> > > +			*log_dablks += *total_dablks;
> > > +			*total_dablks *= 2;
> > > +		}
> > > +	} else {
> > > +		/*
> > > +		 * Out of line attribute, cannot double split, but
> > > +		 * make room for the attribute value itself.
> > > +		 */
> > > +		*rmt_blks = xfs_attr3_rmt_blocks(mp, valuelen);
> > > +	}
> > > +}
> > > +
> > >  /*
> > >   * Set the attribute specified in @args.
> > >   */
> > > @@ -346,6 +367,9 @@ xfs_attr_set(
> > >  	struct xfs_mount	*mp = dp->i_mount;
> > >  	struct xfs_da_args	args;
> > >  	struct xfs_trans_res	tres;
> > > +	unsigned int		log_dablks;
> > > +	unsigned int		rmt_blks;
> > > +	unsigned int		total_dablks;
> > >  	int			rsvd = (flags & ATTR_ROOT) != 0;
> > >  	int			error, local;
> > >  
> > > @@ -361,7 +385,11 @@ xfs_attr_set(
> > >  	args.value = value;
> > >  	args.valuelen = valuelen;
> > >  	args.op_flags = XFS_DA_OP_ADDNAME | XFS_DA_OP_OKNOENT;
> > > -	args.total = xfs_attr_calc_size(&args, &local);
> > > +
> > > +	xfs_attr_calc_size(mp, args.namelen, args.valuelen, &local,
> > > +			&log_dablks, &rmt_blks, &total_dablks);
> > > +
> > > +	args.total = xfs_calc_attr_blocks(mp, total_dablks, rmt_blks);
> > >  
> > >  	error = xfs_qm_dqattach(dp);
> > >  	if (error)
> > > @@ -380,8 +408,8 @@ xfs_attr_set(
> > >  			return error;
> > >  	}
> > >  
> > > -	tres.tr_logres = M_RES(mp)->tr_attrsetm.tr_logres +
> > > -			 M_RES(mp)->tr_attrsetrt.tr_logres * args.total;
> > > +	tres.tr_logres = xfs_calc_attr_res(mp, log_dablks, rmt_blks,
> > > +					total_dablks);
> > >  	tres.tr_logcount = XFS_ATTRSET_LOG_COUNT;
> > >  	tres.tr_logflags = XFS_TRANS_PERM_LOG_RES;
> > >  
> > > diff --git a/fs/xfs/libxfs/xfs_attr.h b/fs/xfs/libxfs/xfs_attr.h
> > > index 94badfa1743e..a1c77618802b 100644
> > > --- a/fs/xfs/libxfs/xfs_attr.h
> > > +++ b/fs/xfs/libxfs/xfs_attr.h
> > > @@ -154,5 +154,8 @@ int xfs_attr_remove_args(struct xfs_da_args *args);
> > >  int xfs_attr_list(struct xfs_inode *dp, char *buffer, int bufsize,
> > >  		  int flags, struct attrlist_cursor_kern *cursor);
> > >  bool xfs_attr_namecheck(const void *name, size_t length);
> > > +void xfs_attr_calc_size(struct xfs_mount *mp, int namelen, int valuelen,
> > > +			int *local, unsigned int *log_dablks,
> > > +			unsigned int *rmt_blks, unsigned int *total_dablks);
> > >  
> > >  #endif	/* __XFS_ATTR_H__ */
> > > diff --git a/fs/xfs/libxfs/xfs_log_rlimit.c b/fs/xfs/libxfs/xfs_log_rlimit.c
> > > index 7f55eb3f3653..33b805411f72 100644
> > > --- a/fs/xfs/libxfs/xfs_log_rlimit.c
> > > +++ b/fs/xfs/libxfs/xfs_log_rlimit.c
> > > @@ -10,6 +10,7 @@
> > >  #include "xfs_log_format.h"
> > >  #include "xfs_trans_resv.h"
> > >  #include "xfs_mount.h"
> > > +#include "xfs_attr.h"
> > >  #include "xfs_da_format.h"
> > >  #include "xfs_trans_space.h"
> > >  #include "xfs_da_btree.h"
> > > @@ -23,17 +24,19 @@ STATIC int
> > >  xfs_log_calc_max_attrsetm_res(
> > >  	struct xfs_mount	*mp)
> > >  {
> > > -	int			size;
> > > -	int			nblks;
> > > +	int		size;
> > > +	int		local;
> > > +	unsigned int	total_dablks;
> > > +	unsigned int	rmt_blks;
> > > +	unsigned int	log_dablks;
> > >  
> > >  	size = xfs_attr_leaf_entsize_local_max(mp->m_attr_geo->blksize) -
> > >  	       MAXNAMELEN - 1;
> > > -	nblks = XFS_DAENTER_SPACE_RES(mp, XFS_ATTR_FORK);
> > > -	nblks += XFS_B_TO_FSB(mp, size);
> > > -	nblks += XFS_NEXTENTADD_SPACE_RES(mp, size, XFS_ATTR_FORK);
> > > +	xfs_attr_calc_size(mp, size, 0, &local, &log_dablks, &rmt_blks,
> > > +			&total_dablks);
> > > +	ASSERT(local == 1);
> > >  
> > > -	return  M_RES(mp)->tr_attrsetm.tr_logres +
> > > -		M_RES(mp)->tr_attrsetrt.tr_logres * nblks;
> > > +	return xfs_calc_attr_res(mp, log_dablks, rmt_blks, total_dablks);
> > >  }
> > >  
> > >  /*
> > > diff --git a/fs/xfs/libxfs/xfs_trans_resv.c b/fs/xfs/libxfs/xfs_trans_resv.c
> > > index 824073a839ac..8a0fea655358 100644
> > > --- a/fs/xfs/libxfs/xfs_trans_resv.c
> > > +++ b/fs/xfs/libxfs/xfs_trans_resv.c
> > > @@ -701,12 +701,10 @@ xfs_calc_attrinval_reservation(
> > >   * Setting an attribute at mount time.
> > >   *	the inode getting the attribute
> > >   *	the superblock for allocations
> > > - *	the agfs extents are allocated from
> > > - *	the attribute btree * max depth
> > > - *	the inode allocation btree
> > > + *	the agf extents are allocated from
> > >   * Since attribute transaction space is dependent on the size of the attribute,
> > >   * the calculation is done partially at mount time and partially at runtime(see
> > > - * below).
> > > + * xfs_attr_calc_size()).
> > >   */
> > >  STATIC uint
> > >  xfs_calc_attrsetm_reservation(
> > > @@ -714,27 +712,7 @@ xfs_calc_attrsetm_reservation(
> > >  {
> > >  	return XFS_DQUOT_LOGRES(mp) +
> > >  		xfs_calc_inode_res(mp, 1) +
> > > -		xfs_calc_buf_res(1, mp->m_sb.sb_sectsize) +
> > > -		xfs_calc_buf_res(XFS_DA_NODE_MAXDEPTH, XFS_FSB_TO_B(mp, 1));
> > > -}
> > > -
> > > -/*
> > > - * Setting an attribute at runtime, transaction space unit per block.
> > > - * 	the superblock for allocations: sector size
> > > - *	the inode bmap btree could join or split: max depth * block size
> > > - * Since the runtime attribute transaction space is dependent on the total
> > > - * blocks needed for the 1st bmap, here we calculate out the space unit for
> > > - * one block so that the caller could figure out the total space according
> > > - * to the attibute extent length in blocks by:
> > > - *	ext * M_RES(mp)->tr_attrsetrt.tr_logres
> > > - */
> > > -STATIC uint
> > > -xfs_calc_attrsetrt_reservation(
> > > -	struct xfs_mount	*mp)
> > > -{
> > > -	return xfs_calc_buf_res(1, mp->m_sb.sb_sectsize) +
> > > -		xfs_calc_buf_res(XFS_BM_MAXLEVELS(mp, XFS_ATTR_FORK),
> > > -				 XFS_FSB_TO_B(mp, 1));
> > > +		xfs_calc_buf_res(2, mp->m_sb.sb_sectsize);
> > 
> > What effect does changing these reservation calculations have on the
> > computed minimum log size?
> > 
> > >  }
> > >  
> > >  /*
> > > @@ -832,6 +810,32 @@ xfs_calc_sb_reservation(
> > >  	return xfs_calc_buf_res(1, mp->m_sb.sb_sectsize);
> > >  }
> > >  
> > > +uint
> > > +xfs_calc_attr_res(
> > > +	struct xfs_mount	*mp,
> > > +	unsigned int		log_dablks,
> > > +	unsigned int		rmt_blks,
> > > +	unsigned int		total_dablks)
> > > +{
> > > +	unsigned int		da_blksize;
> > > +	unsigned int		fs_blksize;
> > > +	unsigned int		bmbt_blks;
> > > +	unsigned int		space_blks;
> > > +
> > > +	bmbt_blks = XFS_NEXTENTADD_SPACE_RES(mp, total_dablks + rmt_blks,
> > > +					XFS_ATTR_FORK);
> > 
> > Pass in the resv structure above and you won't need to calculate this
> > again.
> > 
> > > +	space_blks = xfs_allocfree_log_count(mp,
> > > +					total_dablks + rmt_blks + bmbt_blks);
> > 
> > Only two levels of indent needed here:
> > 
> > 	space_blks = xfs_allocfree_log_count(mp,
> > 			total_dablks + rmt_blks + bmbt_blks);
> > 
> > > +
> > > +	da_blksize = mp->m_attr_geo->blksize;
> > > +	fs_blksize = mp->m_sb.sb_blocksize;
> > 
> > You could probably pass these to xfs_calc_buf_res directly.
> > 
> > I'll give this a spin and see how it does.
> > 
> > --D
> > 
> > > +
> > > +	return M_RES(mp)->tr_attrsetm.tr_logres +
> > > +		xfs_calc_buf_res(log_dablks, da_blksize) +
> > > +		xfs_calc_buf_res(bmbt_blks, fs_blksize) +
> > > +		xfs_calc_buf_res(space_blks, fs_blksize);
> > > +}
> > > +
> > >  void
> > >  xfs_trans_resv_calc(
> > >  	struct xfs_mount	*mp,
> > > @@ -942,7 +946,7 @@ xfs_trans_resv_calc(
> > >  	resp->tr_ichange.tr_logres = xfs_calc_ichange_reservation(mp);
> > >  	resp->tr_fsyncts.tr_logres = xfs_calc_swrite_reservation(mp);
> > >  	resp->tr_writeid.tr_logres = xfs_calc_writeid_reservation(mp);
> > > -	resp->tr_attrsetrt.tr_logres = xfs_calc_attrsetrt_reservation(mp);
> > > +	resp->tr_attrsetrt.tr_logres = 0;
> > >  	resp->tr_clearagi.tr_logres = xfs_calc_clear_agi_bucket_reservation(mp);
> > >  	resp->tr_growrtzero.tr_logres = xfs_calc_growrtzero_reservation(mp);
> > >  	resp->tr_growrtfree.tr_logres = xfs_calc_growrtfree_reservation(mp);
> > > diff --git a/fs/xfs/libxfs/xfs_trans_resv.h b/fs/xfs/libxfs/xfs_trans_resv.h
> > > index 7241ab28cf84..48ceba72fb12 100644
> > > --- a/fs/xfs/libxfs/xfs_trans_resv.h
> > > +++ b/fs/xfs/libxfs/xfs_trans_resv.h
> > > @@ -91,6 +91,8 @@ struct xfs_trans_resv {
> > >  #define	XFS_ATTRSET_LOG_COUNT		3
> > >  #define	XFS_ATTRRM_LOG_COUNT		3
> > >  
> > > +uint xfs_calc_attr_res(struct xfs_mount *mp, unsigned int log_dablks,
> > > +		unsigned int rmt_blks, unsigned int total_dablks);
> > >  void xfs_trans_resv_calc(struct xfs_mount *mp, struct xfs_trans_resv *resp);
> > >  uint xfs_allocfree_log_count(struct xfs_mount *mp, uint num_ops);
> > >  
> > 
> 
> Hi Darrick,
> 
> I agree to the changes you have suggested. I will apply them and post the next
> version soon.
> 
> I will also figure out the effect of this patch on minimum log size.
> 

Darrick, The log space reservation numbers mentioned in response to one of the 
of earlier mails were not correct. I had misinterpreted tr_logres to be in units
of blocks when doing calculations.

Here are the correct numbers,

Without patch
-------------
xattr log reservation space = 555768

With patch
----------
xattr log reservation space = 834936

The changes in xattr log space reservation numbers do not have any effect on
minimum log size calculation. This is because log reservation for truncate
operation is much larger; i.e

tr_logres = 259968, tr_logcount = 8, tr_logflags = 4

... which would be 259968 * 8 = 2079744 bytes

Since 2079744 > 834936, the rest of the calculation for minimum log
reservation does not change.

-- 
chandan






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