From: Ren Lei <[email protected]>
If generation is zero, bypass the verification of generation number
to avoid stale file error. (Be consistent with other fs, such as
ext4, fat, jfs, etc.)
Signed-off-by: Ren Lei<[email protected]>
---
fs/xfs/xfs_export.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/xfs/xfs_export.c b/fs/xfs/xfs_export.c
index 1064c2342876..cbee32c5ad37 100644
--- a/fs/xfs/xfs_export.c
+++ b/fs/xfs/xfs_export.c
@@ -146,7 +146,7 @@ xfs_nfs_get_inode(
return ERR_PTR(error);
}
- if (VFS_I(ip)->i_generation != generation) {
+ if (generation && VFS_I(ip)->i_generation != generation) {
xfs_irele(ip);
return ERR_PTR(-ESTALE);
}
--
2.27.0
On Thu, May 11, 2023 at 06:17:21PM +0800, [email protected] wrote:
> From: Ren Lei <[email protected]>
>
> If generation is zero, bypass the verification of generation number
> to avoid stale file error. (Be consistent with other fs, such as
> ext4, fat, jfs, etc.)
What code is affected by the gen==0 handles being rejected? Is there a
user program or test case where this is required?
--D
> Signed-off-by: Ren Lei<[email protected]>
> ---
> fs/xfs/xfs_export.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/xfs/xfs_export.c b/fs/xfs/xfs_export.c
> index 1064c2342876..cbee32c5ad37 100644
> --- a/fs/xfs/xfs_export.c
> +++ b/fs/xfs/xfs_export.c
> @@ -146,7 +146,7 @@ xfs_nfs_get_inode(
> return ERR_PTR(error);
> }
>
> - if (VFS_I(ip)->i_generation != generation) {
> + if (generation && VFS_I(ip)->i_generation != generation) {
> xfs_irele(ip);
> return ERR_PTR(-ESTALE);
> }
> --
> 2.27.0
>
On Thu, May 11, 2023 at 04:22:06PM -0700, Darrick J. Wong wrote:
> On Thu, May 11, 2023 at 06:17:21PM +0800, [email protected] wrote:
> > From: Ren Lei <[email protected]>
> >
> > If generation is zero, bypass the verification of generation number
> > to avoid stale file error. (Be consistent with other fs, such as
> > ext4, fat, jfs, etc.)
>
> What code is affected by the gen==0 handles being rejected? Is there a
> user program or test case where this is required?
A generation number of 0 is perfectly valid in XFS. We've been
creating them in XFS filesystems since 1993 and never had a problem
with filehandle verification. Indeed, every root inode in every XFS
filesystem ever made will have a generation number of 0.
Yup, a random XFS filesystem recently made from a current xfsprogs:
# xfs_db /dev/vdc
xfs_db> sb 0
xfs_db> a rootino
xfs_db> p core.gen
core.gen = 0
xfs_db>
-Dave.
--
Dave Chinner
[email protected]
On Fri, May 12, 2023 at 10:53:29AM +0800, [email protected] wrote:
> Yup, gen is 0 for the inodes created by libxfs, such as rootino, rbmino, rsumino.
> but those inodes will never be freed, and gen will always zero.
> so I think bypass the verification if gen==0 is still valid.
I disagree. Handles have long encoded inode and generation to prevent
users from unintentionally modifying a file when the inode number is
recycled as a result of an unlink/create cycle.
--D
> Regards,
> Lei
>
> From: Dave Chinner
> Date: 2023-05-12 10:00
> To: Darrick J. Wong
> CC: renlei1; linux-xfs; linux-kernel
> Subject: Re: [PATCH] xfs: xfs_nfs_get_inode support zero generation
> On Thu, May 11, 2023 at 04:22:06PM -0700, Darrick J. Wong wrote:
> > On Thu, May 11, 2023 at 06:17:21PM +0800, [email protected] wrote:
> > > From: Ren Lei <[email protected]>
> > >
> > > If generation is zero, bypass the verification of generation number
> > > to avoid stale file error. (Be consistent with other fs, such as
> > > ext4, fat, jfs, etc.)
> >
> > What code is affected by the gen==0 handles being rejected? Is there a
> > user program or test case where this is required?
>
> A generation number of 0 is perfectly valid in XFS. We've been
> creating them in XFS filesystems since 1993 and never had a problem
> with filehandle verification. Indeed, every root inode in every XFS
> filesystem ever made will have a generation number of 0.
>
> Yup, a random XFS filesystem recently made from a current xfsprogs:
>
> # xfs_db /dev/vdc
> xfs_db> sb 0
> xfs_db> a rootino
> xfs_db> p core.gen
> core.gen = 0
> xfs_db>
>
> -Dave.
> --
> Dave Chinner
> [email protected]
>
On Fri, May 12, 2023 at 10:53:29AM +0800, [email protected] wrote:
> Yup, gen is 0 for the inodes created by libxfs, such as rootino, rbmino, rsumino.
> but those inodes will never be freed, and gen will always zero.
Yes, but why does that even matter for file handle verification?
> so I think bypass the verification if gen==0 is still valid.
Did you think about what happens when an inode->gen
overflows from 0xffffffff to 0 as part of a normal unlink/create
cycle?
-Dave.
--
Dave Chinner
[email protected]