linux-kernel - [PATCH 4/6] fs: xfs: Support atomic write for statx

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Date: Wed, 24 Jan 2024 14:26:43 +0000
From: John Garry <john.g.garry@...cle.com>
To: hch@....de, djwong@...nel.org, viro@...iv.linux.org.uk, brauner@...nel.org,
        dchinner@...hat.com, jack@...e.cz, chandan.babu@...cle.com
Cc: martin.petersen@...cle.com, linux-kernel@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        tytso@....edu, jbongio@...gle.com, ojaswin@...ux.ibm.com,
        John Garry <john.g.garry@...cle.com>
Subject: [PATCH 4/6] 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 | 45 +++++++++++++++++++++++++++++++++++++++++++++
 fs/xfs/xfs_iops.h |  4 ++++
 2 files changed, 49 insertions(+)

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index a0d77f5f512e..0890d2f70f4d 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -546,6 +546,44 @@ xfs_stat_blksize(
 	return PAGE_SIZE;
 }
 
+void xfs_get_atomic_write_attr(
+	struct xfs_inode *ip,
+	unsigned int *unit_min,
+	unsigned int *unit_max)
+{
+	xfs_extlen_t		extsz = xfs_get_extsz(ip);
+	struct xfs_buftarg	*target = xfs_inode_buftarg(ip);
+	struct block_device	*bdev = target->bt_bdev;
+	unsigned int		awu_min, awu_max, align;
+	struct request_queue	*q = bdev->bd_queue;
+	struct xfs_mount	*mp = ip->i_mount;
+
+	/*
+	 * Convert to multiples of the BLOCKSIZE (as we support a minimum
+	 * atomic write unit of BLOCKSIZE).
+	 */
+	awu_min = queue_atomic_write_unit_min_bytes(q);
+	awu_max = queue_atomic_write_unit_max_bytes(q);
+
+	awu_min &= ~mp->m_blockmask;
+	awu_max &= ~mp->m_blockmask;
+
+	align = XFS_FSB_TO_B(mp, extsz);
+
+	if (!awu_max || !xfs_inode_atomicwrites(ip) || !align ||
+	    !is_power_of_2(align)) {
+		*unit_min = 0;
+		*unit_max = 0;
+	} else {
+		if (awu_min)
+			*unit_min = min(awu_min, align);
+		else
+			*unit_min = mp->m_sb.sb_blocksize;
+
+		*unit_max = min(awu_max, align);
+	}
+}
+
 STATIC int
 xfs_vn_getattr(
 	struct mnt_idmap	*idmap,
@@ -619,6 +657,13 @@ 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) {
+			unsigned int unit_min, unit_max;
+
+			xfs_get_atomic_write_attr(ip, &unit_min, &unit_max);
+			generic_fill_statx_atomic_writes(stat,
+				unit_min, unit_max);
+		}
 		fallthrough;
 	default:
 		stat->blksize = xfs_stat_blksize(ip);
diff --git a/fs/xfs/xfs_iops.h b/fs/xfs/xfs_iops.h
index 7f84a0843b24..76dd4c3687aa 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_get_atomic_write_attr(struct xfs_inode *ip,
+		unsigned int *unit_min,
+		unsigned int *unit_max);
+
 #endif /* __XFS_IOPS_H__ */
-- 
2.31.1