Re: [PATCH V11 10/14] xfs: Introduce error injection to reduce maximum inode fork extent count

[Chandan Babu R <chandanrlinux@gmail.com>]

On Thu, 03 Dec 2020 11:06:16 -0800, Darrick J. Wong wrote:
> On Tue, Nov 17, 2020 at 07:14:12PM +0530, Chandan Babu R wrote:
> > This commit adds XFS_ERRTAG_REDUCE_MAX_IEXTENTS error tag which enables
> > userspace programs to test "Inode fork extent count overflow detection"
> > by reducing maximum possible inode fork extent count to 35.
> > 
> > With block size of 4k, xattr (with local value) insert operation would
> > require in the worst case "XFS_DA_NODE_MAXDEPTH + 1" plus
> > "XFS_DA_NODE_MAXDEPTH + (64k / 4k)" (required for guaranteeing removal
> > of a maximum sized xattr) number of extents. This evaluates to ~28
> > extents. To allow for additions of two or more xattrs during extent
> > overflow testing, the pseudo max extent count is set to 35.
> > 
> > Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
> > ---
> >  fs/xfs/libxfs/xfs_errortag.h   | 4 +++-
> >  fs/xfs/libxfs/xfs_inode_fork.c | 4 ++++
> >  fs/xfs/xfs_error.c             | 3 +++
> >  3 files changed, 10 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/xfs/libxfs/xfs_errortag.h b/fs/xfs/libxfs/xfs_errortag.h
> > index 53b305dea381..1c56fcceeea6 100644
> > --- a/fs/xfs/libxfs/xfs_errortag.h
> > +++ b/fs/xfs/libxfs/xfs_errortag.h
> > @@ -56,7 +56,8 @@
> >  #define XFS_ERRTAG_FORCE_SUMMARY_RECALC			33
> >  #define XFS_ERRTAG_IUNLINK_FALLBACK			34
> >  #define XFS_ERRTAG_BUF_IOERROR				35
> > -#define XFS_ERRTAG_MAX					36
> > +#define XFS_ERRTAG_REDUCE_MAX_IEXTENTS			36
> > +#define XFS_ERRTAG_MAX					37
> >  
> >  /*
> >   * Random factors for above tags, 1 means always, 2 means 1/2 time, etc.
> > @@ -97,5 +98,6 @@
> >  #define XFS_RANDOM_FORCE_SUMMARY_RECALC			1
> >  #define XFS_RANDOM_IUNLINK_FALLBACK			(XFS_RANDOM_DEFAULT/10)
> >  #define XFS_RANDOM_BUF_IOERROR				XFS_RANDOM_DEFAULT
> > +#define XFS_RANDOM_REDUCE_MAX_IEXTENTS			1
> >  
> >  #endif /* __XFS_ERRORTAG_H_ */
> > diff --git a/fs/xfs/libxfs/xfs_inode_fork.c b/fs/xfs/libxfs/xfs_inode_fork.c
> > index 8d48716547e5..989b20977654 100644
> > --- a/fs/xfs/libxfs/xfs_inode_fork.c
> > +++ b/fs/xfs/libxfs/xfs_inode_fork.c
> > @@ -24,6 +24,7 @@
> >  #include "xfs_dir2_priv.h"
> >  #include "xfs_attr_leaf.h"
> >  #include "xfs_types.h"
> > +#include "xfs_errortag.h"
> >  
> >  kmem_zone_t *xfs_ifork_zone;
> >  
> > @@ -745,6 +746,9 @@ xfs_iext_count_may_overflow(
> >  
> >  	max_exts = (whichfork == XFS_ATTR_FORK) ? MAXAEXTNUM : MAXEXTNUM;
> >  
> > +	if (XFS_TEST_ERROR(false, ip->i_mount, XFS_ERRTAG_REDUCE_MAX_IEXTENTS))
> > +		max_exts = 35;
> 
> Please add a comment here explaining why 35.

Sure. I will do that.

> 
> Sorry about the longish review delay, last week was a US holiday and
> this week I have eye problems again. :(

Np. Please take care.

> 
> --D
> 
> > +
> >  	nr_exts = ifp->if_nextents + nr_to_add;
> >  	if (nr_exts < ifp->if_nextents || nr_exts > max_exts)
> >  		return -EFBIG;
> > diff --git a/fs/xfs/xfs_error.c b/fs/xfs/xfs_error.c
> > index 7f6e20899473..3780b118cc47 100644
> > --- a/fs/xfs/xfs_error.c
> > +++ b/fs/xfs/xfs_error.c
> > @@ -54,6 +54,7 @@ static unsigned int xfs_errortag_random_default[] = {
> >  	XFS_RANDOM_FORCE_SUMMARY_RECALC,
> >  	XFS_RANDOM_IUNLINK_FALLBACK,
> >  	XFS_RANDOM_BUF_IOERROR,
> > +	XFS_RANDOM_REDUCE_MAX_IEXTENTS,
> >  };
> >  
> >  struct xfs_errortag_attr {
> > @@ -164,6 +165,7 @@ XFS_ERRORTAG_ATTR_RW(force_repair,	XFS_ERRTAG_FORCE_SCRUB_REPAIR);
> >  XFS_ERRORTAG_ATTR_RW(bad_summary,	XFS_ERRTAG_FORCE_SUMMARY_RECALC);
> >  XFS_ERRORTAG_ATTR_RW(iunlink_fallback,	XFS_ERRTAG_IUNLINK_FALLBACK);
> >  XFS_ERRORTAG_ATTR_RW(buf_ioerror,	XFS_ERRTAG_BUF_IOERROR);
> > +XFS_ERRORTAG_ATTR_RW(reduce_max_iextents,	XFS_ERRTAG_REDUCE_MAX_IEXTENTS);
> >  
> >  static struct attribute *xfs_errortag_attrs[] = {
> >  	XFS_ERRORTAG_ATTR_LIST(noerror),
> > @@ -202,6 +204,7 @@ static struct attribute *xfs_errortag_attrs[] = {
> >  	XFS_ERRORTAG_ATTR_LIST(bad_summary),
> >  	XFS_ERRORTAG_ATTR_LIST(iunlink_fallback),
> >  	XFS_ERRORTAG_ATTR_LIST(buf_ioerror),
> > +	XFS_ERRORTAG_ATTR_LIST(reduce_max_iextents),
> >  	NULL,
> >  };
> >  
> 


-- 
chandan