Commit 6a7bb6cc authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Carlos Maiolino
Browse files

xfs: reduce ilock roundtrips in xfs_qm_vop_dqalloc 



xfs_qm_vop_dqalloc only needs the (exclusive) ilock for attaching dquots
to the inode if not done so yet.  All the other locks don't touch the inode
and don't need the ilock - the i_rwsem / iolock protects against changes
to the IDs while we are in a method, and the ilock would not help because
dropping it for the dqget calls would be racy anyway.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
Signed-off-by: default avatarCarlos Maiolino <cem@kernel.org>
parent 13d3c1a0

fs/xfs/xfs_qm.c

+3 −29
Original line number Diff line number Diff line
@@ -1861,16 +1861,12 @@ xfs_qm_vop_dqalloc( 
	struct xfs_dquot	*gq = NULL;

	struct xfs_dquot	*pq = NULL;

	int			error;

	uint			lockflags;



	if (!XFS_IS_QUOTA_ON(mp))

		return 0;



	ASSERT(!xfs_is_metadir_inode(ip));



	lockflags = XFS_ILOCK_EXCL;

	xfs_ilock(ip, lockflags);



	if ((flags & XFS_QMOPT_INHERIT) && XFS_INHERIT_GID(ip))

		gid = inode->i_gid;
@@ -1879,37 +1875,22 @@ xfs_qm_vop_dqalloc( 
	 * if necessary. The dquot(s) will not be locked.

	 */

	if (XFS_NOT_DQATTACHED(mp, ip)) {

		xfs_ilock(ip, XFS_ILOCK_EXCL);

		error = xfs_qm_dqattach_locked(ip, true);

		if (error) {

			xfs_iunlock(ip, lockflags);

		xfs_iunlock(ip, XFS_ILOCK_EXCL);

		if (error)

			return error;

	}

	}



	if ((flags & XFS_QMOPT_UQUOTA) && XFS_IS_UQUOTA_ON(mp)) {

		ASSERT(O_udqpp);

		if (!uid_eq(inode->i_uid, uid)) {

			/*

			 * What we need is the dquot that has this uid, and

			 * if we send the inode to dqget, the uid of the inode

			 * takes priority over what's sent in the uid argument.

			 * We must unlock inode here before calling dqget if

			 * we're not sending the inode, because otherwise

			 * we'll deadlock by doing trans_reserve while

			 * holding ilock.

			 */

			xfs_iunlock(ip, lockflags);

			error = xfs_qm_dqget(mp, from_kuid(user_ns, uid),

					XFS_DQTYPE_USER, true, &uq);

			if (error) {

				ASSERT(error != -ENOENT);

				return error;

			}

			/*

			 * Get the ilock in the right order.

			 */

			lockflags = XFS_ILOCK_SHARED;

			xfs_ilock(ip, lockflags);

		} else {

			/*

			 * Take an extra reference, because we'll return
@@ -1922,15 +1903,12 @@ xfs_qm_vop_dqalloc( 
	if ((flags & XFS_QMOPT_GQUOTA) && XFS_IS_GQUOTA_ON(mp)) {

		ASSERT(O_gdqpp);

		if (!gid_eq(inode->i_gid, gid)) {

			xfs_iunlock(ip, lockflags);

			error = xfs_qm_dqget(mp, from_kgid(user_ns, gid),

					XFS_DQTYPE_GROUP, true, &gq);

			if (error) {

				ASSERT(error != -ENOENT);

				goto error_rele;

			}

			lockflags = XFS_ILOCK_SHARED;

			xfs_ilock(ip, lockflags);

		} else {

			ASSERT(ip->i_gdquot);

			gq = xfs_qm_dqhold(ip->i_gdquot);
@@ -1939,15 +1917,12 @@ xfs_qm_vop_dqalloc( 
	if ((flags & XFS_QMOPT_PQUOTA) && XFS_IS_PQUOTA_ON(mp)) {

		ASSERT(O_pdqpp);

		if (ip->i_projid != prid) {

			xfs_iunlock(ip, lockflags);

			error = xfs_qm_dqget(mp, prid,

					XFS_DQTYPE_PROJ, true, &pq);

			if (error) {

				ASSERT(error != -ENOENT);

				goto error_rele;

			}

			lockflags = XFS_ILOCK_SHARED;

			xfs_ilock(ip, lockflags);

		} else {

			ASSERT(ip->i_pdquot);

			pq = xfs_qm_dqhold(ip->i_pdquot);
@@ -1955,7 +1930,6 @@ xfs_qm_vop_dqalloc( 
	}

	trace_xfs_dquot_dqalloc(ip);



	xfs_iunlock(ip, lockflags);

	if (O_udqpp)

		*O_udqpp = uq;

	else