diff mbox series

[12/29] xfs: enforce GFP_NOIO implicitly during nowait time update

Message ID 20230825135431.1317785-13-hao.xu@linux.dev (mailing list archive)
State New
Headers show
Series io_uring getdents | expand

Commit Message

Hao Xu Aug. 25, 2023, 1:54 p.m. UTC 
From: Hao Xu <howeyxu@tencent.com>

Enforce GFP_NOIO logic implicitly by set pflags if we are in nowait
time update process. Nowait semantics means no waiting for IO,
therefore GFP_NOIO is needed.

Signed-off-by: Hao Xu <howeyxu@tencent.com>
---
 fs/xfs/xfs_iops.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

Comments

Matthew Wilcox Aug. 25, 2023, 2:20 p.m. UTC | #1 
On Fri, Aug 25, 2023 at 09:54:14PM +0800, Hao Xu wrote:
> +++ b/fs/xfs/xfs_iops.c
> @@ -1037,6 +1037,8 @@ xfs_vn_update_time(
>  	int			log_flags = XFS_ILOG_TIMESTAMP;
>  	struct xfs_trans	*tp;
>  	int			error;
> +	int			old_pflags;
> +	bool			nowait = flags & S_NOWAIT;
>  
>  	trace_xfs_update_time(ip);
>  
> @@ -1049,13 +1051,18 @@ xfs_vn_update_time(
>  		log_flags |= XFS_ILOG_CORE;
>  	}
>  
> +	if (nowait)
> +		old_pflags = memalloc_noio_save();
> +
>  	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0, 0, &tp);

This is an abuse of the memalloc_noio_save() interface.  You shouldn't
be setting it around individual allocations; it's the part of the kernel
which decides "I can't afford to do I/O" that should be setting it.
In this case, it should probably be set by io_uring, way way way up at
the top.

But Jens didn't actually answer my question about that:

https://lore.kernel.org/all/ZMhZh2EYPMH1wIXX@casper.infradead.org/
diff mbox series

Patch

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index bf1d4c31f009..5fa391083de9 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1037,6 +1037,8 @@  xfs_vn_update_time(
 	int			log_flags = XFS_ILOG_TIMESTAMP;
 	struct xfs_trans	*tp;
 	int			error;
+	int			old_pflags;
+	bool			nowait = flags & S_NOWAIT;
 
 	trace_xfs_update_time(ip);
 
@@ -1049,13 +1051,18 @@  xfs_vn_update_time(
 		log_flags |= XFS_ILOG_CORE;
 	}
 
+	if (nowait)
+		old_pflags = memalloc_noio_save();
+
 	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0, 0, &tp);
 	if (error)
-		return error;
+		goto out;
 
-	if (flags & S_NOWAIT) {
-		if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL))
-			return -EAGAIN;
+	if (nowait) {
+		if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL)) {
+			error = -EAGAIN;
+			goto out;
+		}
 	} else {
 		xfs_ilock(ip, XFS_ILOCK_EXCL);
 	}
@@ -1069,7 +1076,12 @@  xfs_vn_update_time(
 
 	xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
 	xfs_trans_log_inode(tp, ip, log_flags);
-	return xfs_trans_commit(tp);
+	error = xfs_trans_commit(tp);
+
+out:
+	if (nowait)
+		memalloc_noio_restore(old_pflags);
+	return error;
 }
 
 STATIC int