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Commit be60fe54 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Ben Myers
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xfs: do not read the AGI buffer in xfs_dialloc until nessecary 



Refactor the AG selection loop in xfs_dialloc to operate on the in-memory
perag data as much as possible.  We only read the AGI buffer once we have
selected an AG to allocate inodes now instead of for every AG considered.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
Reviewed-by: default avatarMark Tinguely <tinguely@sgi.com>
Signed-off-by: default avatarBen Myers <bpm@sgi.com>
parent 55d6af64

fs/xfs/xfs_ialloc.c

+69 −58
Original line number Diff line number Diff line
@@ -900,11 +900,10 @@ xfs_dialloc( 
	struct xfs_mount	*mp = tp->t_mountp;

	struct xfs_buf		*agbp;

	xfs_agnumber_t		agno;

	struct xfs_agi		*agi;

	int			error;

	int			ialloced;

	int			noroom = 0;

	xfs_agnumber_t		tagno;

	xfs_agnumber_t		start_agno;

	struct xfs_perag	*pag;



	if (*IO_agbp) {
@@ -921,25 +920,17 @@ xfs_dialloc( 
	 * We do not have an agbp, so select an initial allocation

	 * group for inode allocation.

	 */

	agno = xfs_ialloc_ag_select(tp, parent, mode, okalloc);

	if (agno == NULLAGNUMBER) {

	start_agno = xfs_ialloc_ag_select(tp, parent, mode, okalloc);

	if (start_agno == NULLAGNUMBER) {

		*inop = NULLFSINO;

		return 0;

	}



	error = xfs_ialloc_read_agi(mp, tp, agno, &agbp);

	if (error)

		return XFS_ERROR(error);

	agi = XFS_BUF_TO_AGI(agbp);



	tagno = agno;



	/*

	 * If we have already hit the ceiling of inode blocks then clear

	 * okalloc so we scan all available agi structures for a free

	 * inode.

	 */



	if (mp->m_maxicount &&

	    mp->m_sb.sb_icount + XFS_IALLOC_INODES(mp) > mp->m_maxicount) {

		noroom = 1;
@@ -951,24 +942,56 @@ xfs_dialloc( 
	 * or in which we can allocate some inodes.  Iterate through the

	 * allocation groups upward, wrapping at the end.

	 */

	while (!agi->agi_freecount) {

	agno = start_agno;

	for (;;) {

		pag = xfs_perag_get(mp, agno);

		if (!pag->pagi_inodeok) {

			xfs_ialloc_next_ag(mp);

			goto nextag;

		}



		if (!pag->pagi_init) {

			error = xfs_ialloc_pagi_init(mp, tp, agno);

			if (error)

				goto out_error;

		}



		/*

		 * Don't do anything if we're not supposed to allocate

		 * any blocks, just go on to the next ag.

		 * Do a first racy fast path check if this AG is usable.

		 */

		if (okalloc) {

		if (!pag->pagi_freecount && !okalloc)

			goto nextag;



		error = xfs_ialloc_read_agi(mp, tp, agno, &agbp);

		if (error)

			goto out_error;



		/*

			 * Try to allocate some new inodes in the allocation

			 * group.

		 * Once the AGI has been read in we have to recheck

		 * pagi_freecount with the AGI buffer lock held.

		 */

			if ((error = xfs_ialloc_ag_alloc(tp, agbp, &ialloced))) {

		if (pag->pagi_freecount) {

			xfs_perag_put(pag);

			goto out_alloc;

		}



		if (!okalloc) {

			xfs_trans_brelse(tp, agbp);

			goto nextag;

		}



		error = xfs_ialloc_ag_alloc(tp, agbp, &ialloced);

		if (error) {

			xfs_trans_brelse(tp, agbp);

				if (error == ENOSPC) {



			if (error != ENOSPC)

				goto out_error;



			xfs_perag_put(pag);

			*inop = NULLFSINO;

			return 0;

				} else

					return error;

		}



		if (ialloced) {

			/*

			 * We successfully allocated some inodes, return
@@ -976,42 +999,30 @@ xfs_dialloc( 
			 * can commit the current transaction and call

			 * us again where we left off.

			 */

				ASSERT(be32_to_cpu(agi->agi_freecount) > 0);

			ASSERT(pag->pagi_freecount > 0);

			xfs_perag_put(pag);



			*IO_agbp = agbp;

			*inop = NULLFSINO;

			return 0;

		}

		}

		/*

		 * If it failed, give up on this ag.

		 */

		xfs_trans_brelse(tp, agbp);

		/*

		 * Go on to the next ag: get its ag header.

		 */



nextag:

		if (++tagno == mp->m_sb.sb_agcount)

			tagno = 0;

		if (tagno == agno) {

		xfs_perag_put(pag);

		if (++agno == mp->m_sb.sb_agcount)

			agno = 0;

		if (agno == start_agno) {

			*inop = NULLFSINO;

			return noroom ? ENOSPC : 0;

		}

		pag = xfs_perag_get(mp, tagno);

		if (pag->pagi_inodeok == 0) {

			xfs_perag_put(pag);

			goto nextag;

		}

		error = xfs_ialloc_read_agi(mp, tp, tagno, &agbp);

		xfs_perag_put(pag);

		if (error)

			goto nextag;

		agi = XFS_BUF_TO_AGI(agbp);

		ASSERT(agi->agi_magicnum == cpu_to_be32(XFS_AGI_MAGIC));

	}



out_alloc:

	*IO_agbp = NULL;

	return xfs_dialloc_ag(tp, agbp, parent, inop);

out_error:

	xfs_perag_put(pag);

	return XFS_ERROR(error);

}



/*