On 7/27/21 7:13 PM, Dave Chinner wrote:

On Tue, Jul 27, 2021 at 05:47:57PM -0700, Darrick J. Wong wrote:

quoted

On Mon, Jul 26, 2021 at 11:20:51PM -0700, Allison Henderson wrote:

quoted

This patch adds a mount option to enable delayed attributes. Eventually
this can be removed when delayed attrs becomes permanent.

Signed-off-by: Allison Henderson <redacted>
---
  fs/xfs/libxfs/xfs_attr.h |  2 +-
  fs/xfs/xfs_mount.h       |  1 +
  fs/xfs/xfs_super.c       | 11 ++++++++++-
  fs/xfs/xfs_xattr.c       |  2 ++
  4 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_attr.h b/fs/xfs/libxfs/xfs_attr.h
index c0c92bd3..d4e7521 100644
--- a/fs/xfs/libxfs/xfs_attr.h
+++ b/fs/xfs/libxfs/xfs_attr.h

@@ -30,7 +30,7 @@ struct xfs_attr_list_context;
  
  static inline bool xfs_hasdelattr(struct xfs_mount *mp)
  {
-	return false;
+	return mp->m_flags & XFS_MOUNT_DELATTR;
  }
  
  /*

diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 66a47f5..2945868 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h

@@ -257,6 +257,7 @@ typedef struct xfs_mount {
  #define XFS_MOUNT_NOATTR2	(1ULL << 25)	/* disable use of attr2 format */
  #define XFS_MOUNT_DAX_ALWAYS	(1ULL << 26)
  #define XFS_MOUNT_DAX_NEVER	(1ULL << 27)
+#define XFS_MOUNT_DELATTR	(1ULL << 28)	/* enable delayed attributes */

So uh while we're renaming things away from "delattr", maybe this ...

	LOGGED ATTRIBUTE RE PLAY

... really should become the "larp" debug-only mount option.

	XFS_MOUNT_LARP

Yeah.  Do it!!!

quoted

  /*
   * Max and min values for mount-option defined I/O

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 2c9e26a..39d6645 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c

@@ -94,7 +94,7 @@ enum {
  	Opt_filestreams, Opt_quota, Opt_noquota, Opt_usrquota, Opt_grpquota,
  	Opt_prjquota, Opt_uquota, Opt_gquota, Opt_pquota,
  	Opt_uqnoenforce, Opt_gqnoenforce, Opt_pqnoenforce, Opt_qnoenforce,
-	Opt_discard, Opt_nodiscard, Opt_dax, Opt_dax_enum,
+	Opt_discard, Opt_nodiscard, Opt_dax, Opt_dax_enum, Opt_delattr
  };
  
  static const struct fs_parameter_spec xfs_fs_parameters[] = {

@@ -139,6 +139,7 @@ static const struct fs_parameter_spec xfs_fs_parameters[] = {
  	fsparam_flag("nodiscard",	Opt_nodiscard),
  	fsparam_flag("dax",		Opt_dax),
  	fsparam_enum("dax",		Opt_dax_enum, dax_param_enums),
+	fsparam_flag("delattr",		Opt_delattr),

I think you need this line to be guarded by #ifdefs so that the mount
options parsing code will reject -o larp on non-debug kernels.

As i mentioned on #xfs, this really should be like the "always_cow"
debug option - access it via /sys/fs/xfs/debug/larping_with_larts -
rather than being a mount option that users might accidentally
discover and start using...

Cheers,

Dave.

Sure, if folks are ok with that, I'll take a look at always_cow, and see 
if I can put together something similar for larp.  Or larping_with_larts 
if folks prefer :-)  Thanks for the review!

Allison