From 178231af2bdc14954ee300b3b1bd08e06a1333ea Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Tue, 16 Jan 2024 09:59:44 +1100 Subject: [PATCH] xfs: use an empty transaction for fstrim We currently use a btree walk in the fstrim code. This requires a btree cursor and btree cursors are only used inside transactions except for the fstrim code. This means that all the btree operations that allocate memory operate in both GFP_KERNEL and GFP_NOFS contexts. This causes problems with lockdep being unable to determine the difference between objects that are safe to lock both above and below memory reclaim. Free space btree buffers are definitely locked both above and below reclaim and that means we have to mark all btree infrastructure allocations with GFP_NOFS to avoid potential lockdep false positives. If we wrap this btree walk in an empty cursor, all btree walks are now done under transaction context and so all allocations inherit GFP_NOFS context from the tranaction. This enables us to move all the btree allocations to GFP_KERNEL context and hence help remove the explicit use of GFP_NOFS in XFS. Signed-off-by: Dave Chinner Reviewed-by: "Darrick J. Wong" Signed-off-by: Chandan Babu R --- fs/xfs/xfs_discard.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/fs/xfs/xfs_discard.c b/fs/xfs/xfs_discard.c index 8539f5c9a7744..299b8f9072929 100644 --- a/fs/xfs/xfs_discard.c +++ b/fs/xfs/xfs_discard.c @@ -8,6 +8,7 @@ #include "xfs_format.h" #include "xfs_log_format.h" #include "xfs_trans_resv.h" +#include "xfs_trans.h" #include "xfs_mount.h" #include "xfs_btree.h" #include "xfs_alloc_btree.h" @@ -120,7 +121,7 @@ xfs_discard_extents( error = __blkdev_issue_discard(mp->m_ddev_targp->bt_bdev, XFS_AGB_TO_DADDR(mp, busyp->agno, busyp->bno), XFS_FSB_TO_BB(mp, busyp->length), - GFP_NOFS, &bio); + GFP_KERNEL, &bio); if (error && error != -EOPNOTSUPP) { xfs_info(mp, "discard failed for extent [0x%llx,%u], error %d", @@ -155,6 +156,7 @@ xfs_trim_gather_extents( uint64_t *blocks_trimmed) { struct xfs_mount *mp = pag->pag_mount; + struct xfs_trans *tp; struct xfs_btree_cur *cur; struct xfs_buf *agbp; int error; @@ -168,11 +170,15 @@ xfs_trim_gather_extents( */ xfs_log_force(mp, XFS_LOG_SYNC); - error = xfs_alloc_read_agf(pag, NULL, 0, &agbp); + error = xfs_trans_alloc_empty(mp, &tp); if (error) return error; - cur = xfs_allocbt_init_cursor(mp, NULL, agbp, pag, XFS_BTNUM_CNT); + error = xfs_alloc_read_agf(pag, tp, 0, &agbp); + if (error) + goto out_trans_cancel; + + cur = xfs_allocbt_init_cursor(mp, tp, agbp, pag, XFS_BTNUM_CNT); /* * Look up the extent length requested in the AGF and start with it. @@ -279,7 +285,8 @@ xfs_trim_gather_extents( xfs_extent_busy_clear(mp, &extents->extent_list, false); out_del_cursor: xfs_btree_del_cursor(cur, error); - xfs_buf_relse(agbp); +out_trans_cancel: + xfs_trans_cancel(tp); return error; }