[PATCH 17/21] fs: xfs: iomap atomic write support

John Garry
2023-09-29T10:30:05Z

Ensure that when creating a mapping that we adhere to all the atomic
write rules.

We check that the mapping covers the complete range of the write to ensure
that we'll be just creating a single mapping.

Currently minimum granularity is the FS block size, but it should be
possibly to support lower in future.

Signed-off-by: John Garry <john.g.garry@oracle.com>
---
fs/xfs/xfs_iomap.c | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 70fe873951f3..3424fcfc04f5 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -783,6 +783,7 @@ xfs_direct_write_iomap_begin(
{
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
+ struct xfs_sb *m_sb = &mp->m_sb;
struct xfs_bmbt_irec imap, cmap;
xfs_fileoff_t offset_fsb = XFS_B_TO_FSBT(mp, offset);
xfs_fileoff_t end_fsb = xfs_iomap_end_fsb(mp, offset, length);
@@ -814,6 +815,41 @@ xfs_direct_write_iomap_begin(
if (error)
goto out_unlock;

+ if (flags & IOMAP_ATOMIC_WRITE) {
+ xfs_filblks_t unit_min_fsb, unit_max_fsb;
+
+ xfs_ip_atomic_write_attr(ip, &unit_min_fsb, &unit_max_fsb);
+
+ if (!imap_spans_range(&imap, offset_fsb, end_fsb)) {
+ error = -EIO;
+ goto out_unlock;
+ }
+
+ if (offset % m_sb->sb_blocksize ||
+ length % m_sb->sb_blocksize) {
+ error = -EIO;
+ goto out_unlock;
+ }
+
+ if (imap.br_blockcount == unit_min_fsb ||
+ imap.br_blockcount == unit_max_fsb) {
+ /* min and max must be a power-of-2 */
+ } else if (imap.br_blockcount < unit_min_fsb ||
+ imap.br_blockcount > unit_max_fsb) {
+ error = -EIO;
+ goto out_unlock;
+ } else if (!is_power_of_2(imap.br_blockcount)) {
+ error = -EIO;
+ goto out_unlock;
+ }
+
+ if (imap.br_startoff &&
+ imap.br_startoff % imap.br_blockcount) {
+ error = -EIO;
+ goto out_unlock;
+ }
+ }
+
if (imap_needs_cow(ip, flags, &imap, nimaps)) {
error = -EAGAIN;
if (flags & IOMAP_NOWAIT)
--
2.31.1