[PATCH 24/43] xfs: apply rt extent alignment constraints to CoW extsize hint

Darrick J. Wong
2024-12-13T01:16:30Z

From: Darrick J. Wong <djwong@kernel.org>

The copy-on-write extent size hint is subject to the same alignment
constraints as the regular extent size hint. Since we're in the process
of adding reflink (and therefore CoW) to the realtime device, we must
apply the same scattered rextsize alignment validation strategies to
both hints to deal with the possibility of rextsize changing.

Therefore, fix the inode validator to perform rextsize alignment checks
on regular realtime files, and to remove misaligned directory hints.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
fs/xfs/libxfs/xfs_inode_buf.c | 25 ++++++++++++++++++++-----
fs/xfs/xfs_inode_item.c | 14 ++++++++++++++
fs/xfs/xfs_ioctl.c | 17 +++++++++++++++--
3 files changed, 49 insertions(+), 7 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index 4273d096fb0a9c..f24fa628fecf1e 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -910,11 +910,29 @@ xfs_inode_validate_cowextsize(
bool rt_flag;
bool hint_flag;
uint32_t cowextsize_bytes;
+ uint32_t blocksize_bytes;

rt_flag = (flags & XFS_DIFLAG_REALTIME);
hint_flag = (flags2 & XFS_DIFLAG2_COWEXTSIZE);
cowextsize_bytes = XFS_FSB_TO_B(mp, cowextsize);

+ /*
+ * Similar to extent size hints, a directory can be configured to
+ * propagate realtime status and a CoW extent size hint to newly
+ * created files even if there is no realtime device, and the hints on
+ * disk can become misaligned if the sysadmin changes the rt extent
+ * size while adding the realtime device.
+ *
+ * Therefore, we can only enforce the rextsize alignment check against
+ * regular realtime files, and rely on callers to decide when alignment
+ * checks are appropriate, and fix things up as needed.
+ */
+
+ if (rt_flag)
+ blocksize_bytes = XFS_FSB_TO_B(mp, mp->m_sb.sb_rextsize);
+ else
+ blocksize_bytes = mp->m_sb.sb_blocksize;
+
if (hint_flag && !xfs_has_reflink(mp))
return __this_address;

@@ -928,16 +946,13 @@ xfs_inode_validate_cowextsize(
if (mode && !hint_flag && cowextsize != 0)
return __this_address;

- if (hint_flag && rt_flag)
- return __this_address;
-
- if (cowextsize_bytes % mp->m_sb.sb_blocksize)
+ if (cowextsize_bytes % blocksize_bytes)
return __this_address;

if (cowextsize > XFS_MAX_BMBT_EXTLEN)
return __this_address;

- if (cowextsize > mp->m_sb.sb_agblocks / 2)
+ if (!rt_flag && cowextsize > mp->m_sb.sb_agblocks / 2)
return __this_address;

return NULL;
diff --git a/fs/xfs/xfs_inode_item.c b/fs/xfs/xfs_inode_item.c
index a174f64b8bb250..70283c6419fd30 100644
--- a/fs/xfs/xfs_inode_item.c
+++ b/fs/xfs/xfs_inode_item.c
@@ -157,6 +157,20 @@ xfs_inode_item_precommit(
if (flags & XFS_ILOG_IVERSION)
flags = ((flags & ~XFS_ILOG_IVERSION) | XFS_ILOG_CORE);

+ /*
+ * Inode verifiers do not check that the CoW extent size hint is an
+ * integer multiple of the rt extent size on a directory with both
+ * rtinherit and cowextsize flags set. If we're logging a directory
+ * that is misconfigured in this way, clear the hint.
+ */
+ if ((ip->i_diflags & XFS_DIFLAG_RTINHERIT) &&
+ (ip->i_diflags2 & XFS_DIFLAG2_COWEXTSIZE) &&
+ xfs_extlen_to_rtxmod(ip->i_mount, ip->i_cowextsize) > 0) {
+ ip->i_diflags2 &= ~XFS_DIFLAG2_COWEXTSIZE;
+ ip->i_cowextsize = 0;
+ flags |= XFS_ILOG_CORE;
+ }
+
if (!iip->ili_item.li_buf) {
struct xfs_buf *bp;
int error;
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 4caf29cc59b9ef..726282e74d546d 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -469,8 +469,21 @@ xfs_fill_fsxattr(
}
}

- if (ip->i_diflags2 & XFS_DIFLAG2_COWEXTSIZE)
- fa->fsx_cowextsize = XFS_FSB_TO_B(mp, ip->i_cowextsize);
+ if (ip->i_diflags2 & XFS_DIFLAG2_COWEXTSIZE) {
+ /*
+ * Don't let a misaligned CoW extent size hint on a directory
+ * escape to userspace if it won't pass the setattr checks
+ * later.
+ */
+ if ((ip->i_diflags & XFS_DIFLAG_RTINHERIT) &&
+ ip->i_cowextsize % mp->m_sb.sb_rextsize > 0) {
+ fa->fsx_xflags &= ~FS_XFLAG_COWEXTSIZE;
+ fa->fsx_cowextsize = 0;
+ } else {
+ fa->fsx_cowextsize = XFS_FSB_TO_B(mp, ip->i_cowextsize);
+ }
+ }
+
fa->fsx_projid = ip->i_projid;
if (ifp && !xfs_need_iread_extents(ifp))
fa->fsx_nextents = xfs_iext_count(ifp);