| Message ID | 164685376731.496011.1567771444928519597.stgit@magnolia (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | xfs: constify dotdot global variable | expand |
On Wed, Mar 09, 2022 at 11:22:47AM -0800, Darrick J. Wong wrote: > From: Darrick J. Wong <djwong@kernel.org> > > The symbol xfs_name_dotdot is a global variable that the xfs codebase > uses here and there to look up directory dotdot entries. Currently it's > a non-const variable, which means that it's a mutable global variable. > So far nobody's abused this to cause problems, but let's use the > compiler to enforce that. > > Signed-off-by: Darrick J. Wong <djwong@kernel.org> > --- > fs/xfs/libxfs/xfs_dir2.c | 6 +++++- > fs/xfs/libxfs/xfs_dir2.h | 2 +- > fs/xfs/scrub/parent.c | 6 ++++-- > fs/xfs/xfs_export.c | 3 ++- > 4 files changed, 12 insertions(+), 5 deletions(-) > > > diff --git a/fs/xfs/libxfs/xfs_dir2.c b/fs/xfs/libxfs/xfs_dir2.c > index a77d931d65a3..cf9fa07e62d5 100644 > --- a/fs/xfs/libxfs/xfs_dir2.c > +++ b/fs/xfs/libxfs/xfs_dir2.c > @@ -19,7 +19,11 @@ > #include "xfs_error.h" > #include "xfs_trace.h" > > -struct xfs_name xfs_name_dotdot = { (unsigned char *)"..", 2, XFS_DIR3_FT_DIR }; > +const struct xfs_name xfs_name_dotdot = { > + .name = (unsigned char *)"..", > + .len = 2, > + .type = XFS_DIR3_FT_DIR, > +}; *nod* > diff --git a/fs/xfs/scrub/parent.c b/fs/xfs/scrub/parent.c > index ab182a5cd0c0..e9549d998cdc 100644 > --- a/fs/xfs/scrub/parent.c > +++ b/fs/xfs/scrub/parent.c > @@ -131,6 +131,7 @@ xchk_parent_validate( > xfs_ino_t dnum, > bool *try_again) > { > + struct xfs_name dotdot = xfs_name_dotdot; > struct xfs_mount *mp = sc->mp; > struct xfs_inode *dp = NULL; > xfs_nlink_t expected_nlink; > @@ -230,7 +231,7 @@ xchk_parent_validate( > expected_nlink = VFS_I(sc->ip)->i_nlink == 0 ? 0 : 1; > > /* Look up '..' to see if the inode changed. */ > - error = xfs_dir_lookup(sc->tp, sc->ip, &xfs_name_dotdot, &dnum, NULL); > + error = xfs_dir_lookup(sc->tp, sc->ip, &dotdot, &dnum, NULL); > if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error)) > goto out_rele; > Why can't xfs_dir_lookup() be defined as a const xname for the input name? All it does is extract the contents into the da_args fields, and pass it to xfs_dir_hashname() which you converted to const in the previous patch. Or does the compiler then complain at all the other callsites that you're passing non-const stuff to const function parameters? i.e. am I just pulling on another dangling end of the ball of string at this point? > @@ -263,6 +264,7 @@ int > xchk_parent( > struct xfs_scrub *sc) > { > + struct xfs_name dotdot = xfs_name_dotdot; > struct xfs_mount *mp = sc->mp; > xfs_ino_t dnum; > bool try_again; > @@ -293,7 +295,7 @@ xchk_parent( > xfs_iunlock(sc->ip, XFS_ILOCK_EXCL | XFS_MMAPLOCK_EXCL); > > /* Look up '..' */ > - error = xfs_dir_lookup(sc->tp, sc->ip, &xfs_name_dotdot, &dnum, NULL); > + error = xfs_dir_lookup(sc->tp, sc->ip, &dotdot, &dnum, NULL); > if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error)) > goto out; > if (!xfs_verify_dir_ino(mp, dnum)) { > diff --git a/fs/xfs/xfs_export.c b/fs/xfs/xfs_export.c > index 1064c2342876..8939119191f4 100644 > --- a/fs/xfs/xfs_export.c > +++ b/fs/xfs/xfs_export.c > @@ -206,10 +206,11 @@ STATIC struct dentry * > xfs_fs_get_parent( > struct dentry *child) > { > + struct xfs_name dotdot = xfs_name_dotdot; > int error; > struct xfs_inode *cip; > > - error = xfs_lookup(XFS_I(d_inode(child)), &xfs_name_dotdot, &cip, NULL); > + error = xfs_lookup(XFS_I(d_inode(child)), &dotdot, &cip, NULL); > if (unlikely(error)) > return ERR_PTR(error); This only calls xfs_dir_lookup() with name, so if xfs_dir_lookup() can have a const name, so can xfs_lookup().... Cheers, Dave.
On Thu, Mar 10, 2022 at 09:32:45AM +1100, Dave Chinner wrote: > On Wed, Mar 09, 2022 at 11:22:47AM -0800, Darrick J. Wong wrote: > > From: Darrick J. Wong <djwong@kernel.org> > > > > The symbol xfs_name_dotdot is a global variable that the xfs codebase > > uses here and there to look up directory dotdot entries. Currently it's > > a non-const variable, which means that it's a mutable global variable. > > So far nobody's abused this to cause problems, but let's use the > > compiler to enforce that. > > > > Signed-off-by: Darrick J. Wong <djwong@kernel.org> > > --- > > fs/xfs/libxfs/xfs_dir2.c | 6 +++++- > > fs/xfs/libxfs/xfs_dir2.h | 2 +- > > fs/xfs/scrub/parent.c | 6 ++++-- > > fs/xfs/xfs_export.c | 3 ++- > > 4 files changed, 12 insertions(+), 5 deletions(-) > > > > > > diff --git a/fs/xfs/libxfs/xfs_dir2.c b/fs/xfs/libxfs/xfs_dir2.c > > index a77d931d65a3..cf9fa07e62d5 100644 > > --- a/fs/xfs/libxfs/xfs_dir2.c > > +++ b/fs/xfs/libxfs/xfs_dir2.c > > @@ -19,7 +19,11 @@ > > #include "xfs_error.h" > > #include "xfs_trace.h" > > > > -struct xfs_name xfs_name_dotdot = { (unsigned char *)"..", 2, XFS_DIR3_FT_DIR }; > > +const struct xfs_name xfs_name_dotdot = { > > + .name = (unsigned char *)"..", > > + .len = 2, > > + .type = XFS_DIR3_FT_DIR, > > +}; > > *nod* > > > diff --git a/fs/xfs/scrub/parent.c b/fs/xfs/scrub/parent.c > > index ab182a5cd0c0..e9549d998cdc 100644 > > --- a/fs/xfs/scrub/parent.c > > +++ b/fs/xfs/scrub/parent.c > > @@ -131,6 +131,7 @@ xchk_parent_validate( > > xfs_ino_t dnum, > > bool *try_again) > > { > > + struct xfs_name dotdot = xfs_name_dotdot; > > struct xfs_mount *mp = sc->mp; > > struct xfs_inode *dp = NULL; > > xfs_nlink_t expected_nlink; > > @@ -230,7 +231,7 @@ xchk_parent_validate( > > expected_nlink = VFS_I(sc->ip)->i_nlink == 0 ? 0 : 1; > > > > /* Look up '..' to see if the inode changed. */ > > - error = xfs_dir_lookup(sc->tp, sc->ip, &xfs_name_dotdot, &dnum, NULL); > > + error = xfs_dir_lookup(sc->tp, sc->ip, &dotdot, &dnum, NULL); > > if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error)) > > goto out_rele; > > > > Why can't xfs_dir_lookup() be defined as a const xname for the input > name? All it does is extract the contents into the da_args fields, > and pass it to xfs_dir_hashname() which you converted to const in > the previous patch. The metadata directory patchset changes xfs_dir_lookup to return the ftype in the dirent so that it can bail early if the dirent doesn't point to the filetype that we want. I wouldn't be /that/ sad to remove that bit of functionality in favor of constifying the name parameter to xfs_dir_lookup. Thinking about this more, I think the metadir code could implement its own lookup dispatch function that /does/ return the dirent ftype, since the sf/block/node/leaf functions all live in libxfs anyway. > Or does the compiler then complain at all the other callsites that > you're passing non-const stuff to const function parameters? i.e. am > I just pulling on another dangling end of the ball of string at this > point? Nope, just djwong-dev blindness. :( > > @@ -263,6 +264,7 @@ int > > xchk_parent( > > struct xfs_scrub *sc) > > { > > + struct xfs_name dotdot = xfs_name_dotdot; > > struct xfs_mount *mp = sc->mp; > > xfs_ino_t dnum; > > bool try_again; > > @@ -293,7 +295,7 @@ xchk_parent( > > xfs_iunlock(sc->ip, XFS_ILOCK_EXCL | XFS_MMAPLOCK_EXCL); > > > > /* Look up '..' */ > > - error = xfs_dir_lookup(sc->tp, sc->ip, &xfs_name_dotdot, &dnum, NULL); > > + error = xfs_dir_lookup(sc->tp, sc->ip, &dotdot, &dnum, NULL); > > if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error)) > > goto out; > > if (!xfs_verify_dir_ino(mp, dnum)) { > > diff --git a/fs/xfs/xfs_export.c b/fs/xfs/xfs_export.c > > index 1064c2342876..8939119191f4 100644 > > --- a/fs/xfs/xfs_export.c > > +++ b/fs/xfs/xfs_export.c > > @@ -206,10 +206,11 @@ STATIC struct dentry * > > xfs_fs_get_parent( > > struct dentry *child) > > { > > + struct xfs_name dotdot = xfs_name_dotdot; > > int error; > > struct xfs_inode *cip; > > > > - error = xfs_lookup(XFS_I(d_inode(child)), &xfs_name_dotdot, &cip, NULL); > > + error = xfs_lookup(XFS_I(d_inode(child)), &dotdot, &cip, NULL); > > if (unlikely(error)) > > return ERR_PTR(error); > > This only calls xfs_dir_lookup() with name, so if xfs_dir_lookup() > can have a const name, so can xfs_lookup().... Yep. I'll fix that in the next version. --D > Cheers, > > Dave. > -- > Dave Chinner > david@fromorbit.com
diff --git a/fs/xfs/libxfs/xfs_dir2.c b/fs/xfs/libxfs/xfs_dir2.c index a77d931d65a3..cf9fa07e62d5 100644 --- a/fs/xfs/libxfs/xfs_dir2.c +++ b/fs/xfs/libxfs/xfs_dir2.c @@ -19,7 +19,11 @@ #include "xfs_error.h" #include "xfs_trace.h" -struct xfs_name xfs_name_dotdot = { (unsigned char *)"..", 2, XFS_DIR3_FT_DIR }; +const struct xfs_name xfs_name_dotdot = { + .name = (unsigned char *)"..", + .len = 2, + .type = XFS_DIR3_FT_DIR, +}; /* * Convert inode mode to directory entry filetype diff --git a/fs/xfs/libxfs/xfs_dir2.h b/fs/xfs/libxfs/xfs_dir2.h index f7e6cc869c13..3120d1da9d68 100644 --- a/fs/xfs/libxfs/xfs_dir2.h +++ b/fs/xfs/libxfs/xfs_dir2.h @@ -21,7 +21,7 @@ struct xfs_dir2_data_unused; struct xfs_dir3_icfree_hdr; struct xfs_dir3_icleaf_hdr; -extern struct xfs_name xfs_name_dotdot; +extern const struct xfs_name xfs_name_dotdot; /* * Convert inode mode to directory entry filetype diff --git a/fs/xfs/scrub/parent.c b/fs/xfs/scrub/parent.c index ab182a5cd0c0..e9549d998cdc 100644 --- a/fs/xfs/scrub/parent.c +++ b/fs/xfs/scrub/parent.c @@ -131,6 +131,7 @@ xchk_parent_validate( xfs_ino_t dnum, bool *try_again) { + struct xfs_name dotdot = xfs_name_dotdot; struct xfs_mount *mp = sc->mp; struct xfs_inode *dp = NULL; xfs_nlink_t expected_nlink; @@ -230,7 +231,7 @@ xchk_parent_validate( expected_nlink = VFS_I(sc->ip)->i_nlink == 0 ? 0 : 1; /* Look up '..' to see if the inode changed. */ - error = xfs_dir_lookup(sc->tp, sc->ip, &xfs_name_dotdot, &dnum, NULL); + error = xfs_dir_lookup(sc->tp, sc->ip, &dotdot, &dnum, NULL); if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error)) goto out_rele; @@ -263,6 +264,7 @@ int xchk_parent( struct xfs_scrub *sc) { + struct xfs_name dotdot = xfs_name_dotdot; struct xfs_mount *mp = sc->mp; xfs_ino_t dnum; bool try_again; @@ -293,7 +295,7 @@ xchk_parent( xfs_iunlock(sc->ip, XFS_ILOCK_EXCL | XFS_MMAPLOCK_EXCL); /* Look up '..' */ - error = xfs_dir_lookup(sc->tp, sc->ip, &xfs_name_dotdot, &dnum, NULL); + error = xfs_dir_lookup(sc->tp, sc->ip, &dotdot, &dnum, NULL); if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error)) goto out; if (!xfs_verify_dir_ino(mp, dnum)) { diff --git a/fs/xfs/xfs_export.c b/fs/xfs/xfs_export.c index 1064c2342876..8939119191f4 100644 --- a/fs/xfs/xfs_export.c +++ b/fs/xfs/xfs_export.c @@ -206,10 +206,11 @@ STATIC struct dentry * xfs_fs_get_parent( struct dentry *child) { + struct xfs_name dotdot = xfs_name_dotdot; int error; struct xfs_inode *cip; - error = xfs_lookup(XFS_I(d_inode(child)), &xfs_name_dotdot, &cip, NULL); + error = xfs_lookup(XFS_I(d_inode(child)), &dotdot, &cip, NULL); if (unlikely(error)) return ERR_PTR(error);