[PATCH 10/12] xfs: place the CIL under nofs allocation context

Dave Chinner
2024-01-15T23:01:22Z

From: Dave Chinner <dchinner@redhat.com>

This is core code that needs to run in low memory conditions and
can be triggered from memory reclaim. While it runs in a workqueue,
it really shouldn't be recursing back into the filesystem during
any memory allocation it needs to function.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
fs/xfs/xfs_log_cil.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index 815a2181004c..8c3b09777006 100644
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -100,7 +100,7 @@ xlog_cil_ctx_alloc(void)
{
struct xfs_cil_ctx *ctx;

- ctx = kzalloc(sizeof(*ctx), GFP_NOFS | __GFP_NOFAIL);
+ ctx = kzalloc(sizeof(*ctx), GFP_KERNEL | __GFP_NOFAIL);
INIT_LIST_HEAD(&ctx->committing);
INIT_LIST_HEAD(&ctx->busy_extents.extent_list);
INIT_LIST_HEAD(&ctx->log_items);
@@ -1116,11 +1116,18 @@ xlog_cil_cleanup_whiteouts(
* same sequence twice. If we get a race between multiple pushes for the same
* sequence they will block on the first one and then abort, hence avoiding
* needless pushes.
+ *
+ * This runs from a workqueue so it does not inherent any specific memory
+ * allocation context. However, we do not want to block on memory reclaim
+ * recursing back into the filesystem because this push may have been triggered
+ * by memory reclaim itself. Hence we really need to run under full GFP_NOFS
+ * contraints here.
*/
static void
xlog_cil_push_work(
struct work_struct *work)
{
+ unsigned int nofs_flags = memalloc_nofs_save();
struct xfs_cil_ctx *ctx =
container_of(work, struct xfs_cil_ctx, push_work);
struct xfs_cil *cil = ctx->cil;
@@ -1334,12 +1341,14 @@ xlog_cil_push_work(
spin_unlock(&log->l_icloglock);
xlog_cil_cleanup_whiteouts(&whiteouts);
xfs_log_ticket_ungrant(log, ticket);
+ memalloc_nofs_restore(nofs_flags);
return;

out_skip:
up_write(&cil->xc_ctx_lock);
xfs_log_ticket_put(new_ctx->ticket);
kfree(new_ctx);
+ memalloc_nofs_restore(nofs_flags);
return;

out_abort_free_ticket:
@@ -1348,6 +1357,7 @@ xlog_cil_push_work(
if (!ctx->commit_iclog) {
xfs_log_ticket_ungrant(log, ctx->ticket);
xlog_cil_committed(ctx);
+ memalloc_nofs_restore(nofs_flags);
return;
}
spin_lock(&log->l_icloglock);
@@ -1356,6 +1366,7 @@ xlog_cil_push_work(
/* Not safe to reference ctx now! */
spin_unlock(&log->l_icloglock);
xfs_log_ticket_ungrant(log, ticket);
+ memalloc_nofs_restore(nofs_flags);
}

/*
--
2.43.0