linux-kernel - [PATCH 15/21] fs: xfs: Support atomic write for statx

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Message-Id: <20230929102726.2985188-16-john.g.garry@oracle.com>
Date:   Fri, 29 Sep 2023 10:27:20 +0000
From:   John Garry <john.g.garry@...cle.com>
To:     axboe@...nel.dk, kbusch@...nel.org, hch@....de, sagi@...mberg.me,
        jejb@...ux.ibm.com, martin.petersen@...cle.com, djwong@...nel.org,
        viro@...iv.linux.org.uk, brauner@...nel.org,
        chandan.babu@...cle.com, dchinner@...hat.com
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nvme@...ts.infradead.org, linux-xfs@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, tytso@....edu, jbongio@...gle.com,
        linux-api@...r.kernel.org, John Garry <john.g.garry@...cle.com>
Subject: [PATCH 15/21] fs: xfs: Support atomic write for statx

Support providing info on atomic write unit min and max for an inode.

For simplicity, currently we limit the min at the FS block size, but a
lower limit could be supported in future.

The atomic write unit min and max is limited by the guaranteed extent
alignment for the inode.

Signed-off-by: John Garry <john.g.garry@...cle.com>
---
 fs/xfs/xfs_iops.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++
 fs/xfs/xfs_iops.h |  4 ++++
 2 files changed, 55 insertions(+)

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 1c1e6171209d..5bff80748223 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -546,6 +546,46 @@ xfs_stat_blksize(
 	return PAGE_SIZE;
 }
 
+void xfs_ip_atomic_write_attr(struct xfs_inode *ip,
+			xfs_filblks_t *unit_min_fsb,
+			xfs_filblks_t *unit_max_fsb)
+{
+	xfs_extlen_t		extsz_hint = xfs_get_extsz_hint(ip);
+	struct xfs_buftarg	*target = xfs_inode_buftarg(ip);
+	struct block_device	*bdev = target->bt_bdev;
+	struct xfs_mount	*mp = ip->i_mount;
+	xfs_filblks_t		atomic_write_unit_min,
+				atomic_write_unit_max,
+				align;
+
+	atomic_write_unit_min = XFS_B_TO_FSB(mp,
+		queue_atomic_write_unit_min_bytes(bdev->bd_queue));
+	atomic_write_unit_max = XFS_B_TO_FSB(mp,
+		queue_atomic_write_unit_max_bytes(bdev->bd_queue));
+
+	/* for RT, unset extsize gives hint of 1 */
+	/* for !RT, unset extsize gives hint of 0 */
+	if (extsz_hint && (XFS_IS_REALTIME_INODE(ip) ||
+	    (ip->i_diflags2 & XFS_DIFLAG2_FORCEALIGN)))
+		align = extsz_hint;
+	else
+		align = 1;
+
+	if (atomic_write_unit_max == 0) {
+		*unit_min_fsb = 0;
+		*unit_max_fsb = 0;
+	} else if (atomic_write_unit_min == 0) {
+		*unit_min_fsb = 1;
+		*unit_max_fsb = min_t(xfs_filblks_t, atomic_write_unit_max,
+					align);
+	} else {
+		*unit_min_fsb = min_t(xfs_filblks_t, atomic_write_unit_min,
+					align);
+		*unit_max_fsb = min_t(xfs_filblks_t, atomic_write_unit_max,
+					align);
+	}
+}
+
 STATIC int
 xfs_vn_getattr(
 	struct mnt_idmap	*idmap,
@@ -614,6 +654,17 @@ xfs_vn_getattr(
 			stat->dio_mem_align = bdev_dma_alignment(bdev) + 1;
 			stat->dio_offset_align = bdev_logical_block_size(bdev);
 		}
+		if (request_mask & STATX_WRITE_ATOMIC) {
+			xfs_filblks_t unit_min_fsb, unit_max_fsb;
+
+			xfs_ip_atomic_write_attr(ip, &unit_min_fsb,
+				&unit_max_fsb);
+			stat->atomic_write_unit_min = XFS_FSB_TO_B(mp, unit_min_fsb);
+			stat->atomic_write_unit_max = XFS_FSB_TO_B(mp, unit_max_fsb);
+			stat->attributes |= STATX_ATTR_WRITE_ATOMIC;
+			stat->attributes_mask |= STATX_ATTR_WRITE_ATOMIC;
+			stat->result_mask |= STATX_WRITE_ATOMIC;
+		}
 		fallthrough;
 	default:
 		stat->blksize = xfs_stat_blksize(ip);
diff --git a/fs/xfs/xfs_iops.h b/fs/xfs/xfs_iops.h
index 7f84a0843b24..b1e683b04301 100644
--- a/fs/xfs/xfs_iops.h
+++ b/fs/xfs/xfs_iops.h
@@ -19,4 +19,8 @@ int xfs_vn_setattr_size(struct mnt_idmap *idmap,
 int xfs_inode_init_security(struct inode *inode, struct inode *dir,
 		const struct qstr *qstr);
 
+void xfs_ip_atomic_write_attr(struct xfs_inode *ip,
+			xfs_filblks_t *unit_min_fsb,
+			xfs_filblks_t *unit_max_fsb);
+
 #endif /* __XFS_IOPS_H__ */
-- 
2.31.1