On Tue, Apr 08, 2025 at 01:00:53PM -0700, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@xxxxxx>
>
> Commit 9748cb2dc393 ("VFS: repack DENTRY_ flags.") changed the value of
> DCACHE_MOUNTED, which broke drgn's path_lookup() helper. drgn is forced
> to hard-code it because it's a macro, and macros aren't preserved in
> debugging information by default.
>
> Enums, on the other hand, are included in debugging information. Convert
> the DCACHE_* flag macros to an enum so that debugging tools like drgn
> and bpftrace can make use of them.
Ok, that's fine and I prefer them anyway.
>
> Link: https://github.com/osandov/drgn/blob/2027d0fea84d74b835e77392f7040c2a333180c6/drgn/helpers/linux/fs.py#L43-L46
> Signed-off-by: Omar Sandoval <osandov@xxxxxx>
> ---
> Hi,
>
> This is based on Linus' tree as of today. If possible, it'd be great to
> get this in for 6.15.
>
> Here are a couple of examples of similar changes in the past:
>
> 0b108e83795c ("SUNRPC: convert RPC_TASK_* constants to enum")
> ff202303c398 ("mm: convert page type macros to enum")
>
> There's also an alternative approach that is more verbose but allows for
> automatic numbering:
Meh, no need imho.
>
> enum dentry_flags {
> __DCACHE_OP_HASH,
> __DCACHE_OP_COMPARE,
> ...
> };
>
> #define DCACHE_OP_HASH BIT(__DCACHE_OP_HASH)
> #define DCACHE_OP_COMPARE BIT(__DCACHE_OP_COMPARE)
> ...
>
> Let me know if you'd prefer that approach.
>
> Thanks,
> Omar
>
> include/linux/dcache.h | 105 ++++++++++++++++++++---------------------
> 1 file changed, 50 insertions(+), 55 deletions(-)
>
> diff --git a/include/linux/dcache.h b/include/linux/dcache.h
> index 8d1395f945bf..a945cc86a8f1 100644
> --- a/include/linux/dcache.h
> +++ b/include/linux/dcache.h
> @@ -173,65 +173,60 @@ struct dentry_operations {
> */
>
> /* d_flags entries */
> -#define DCACHE_OP_HASH BIT(0)
> -#define DCACHE_OP_COMPARE BIT(1)
> -#define DCACHE_OP_REVALIDATE BIT(2)
> -#define DCACHE_OP_DELETE BIT(3)
> -#define DCACHE_OP_PRUNE BIT(4)
> +enum dentry_flags {
> + DCACHE_OP_HASH = BIT(0),
> + DCACHE_OP_COMPARE = BIT(1),
> + DCACHE_OP_REVALIDATE = BIT(2),
> + DCACHE_OP_DELETE = BIT(3),
> + DCACHE_OP_PRUNE = BIT(4),
> + /*
> + * This dentry is possibly not currently connected to the dcache tree,
> + * in which case its parent will either be itself, or will have this
> + * flag as well. nfsd will not use a dentry with this bit set, but will
> + * first endeavour to clear the bit either by discovering that it is
> + * connected, or by performing lookup operations. Any filesystem which
> + * supports nfsd_operations MUST have a lookup function which, if it
> + * finds a directory inode with a DCACHE_DISCONNECTED dentry, will
> + * d_move that dentry into place and return that dentry rather than the
> + * passed one, typically using d_splice_alias.
> + */
> + DCACHE_DISCONNECTED = BIT(5),
> + DCACHE_REFERENCED = BIT(6), /* Recently used, don't discard. */
> + DCACHE_DONTCACHE = BIT(7), /* Purge from memory on final dput() */
> + DCACHE_CANT_MOUNT = BIT(8),
> + DCACHE_GENOCIDE = BIT(9),
> + DCACHE_SHRINK_LIST = BIT(10),
> + DCACHE_OP_WEAK_REVALIDATE = BIT(11),
> + /*
> + * this dentry has been "silly renamed" and has to be deleted on the
> + * last dput()
> + */
> + DCACHE_NFSFS_RENAMED = BIT(12),
> + /* Parent inode is watched by some fsnotify listener */
> + DCACHE_FSNOTIFY_PARENT_WATCHED = BIT(13),
> + DCACHE_DENTRY_KILLED = BIT(14),
> + DCACHE_MOUNTED = BIT(15), /* is a mountpoint */
> + DCACHE_NEED_AUTOMOUNT = BIT(16), /* handle automount on this dir */
> + DCACHE_MANAGE_TRANSIT = BIT(17), /* manage transit from this dirent */
> + DCACHE_LRU_LIST = BIT(18),
> + DCACHE_ENTRY_TYPE = (7 << 19), /* bits 19..21 are for storing type: */
> + DCACHE_MISS_TYPE = (0 << 19), /* Negative dentry */
> + DCACHE_WHITEOUT_TYPE = (1 << 19), /* Whiteout dentry (stop pathwalk) */
> + DCACHE_DIRECTORY_TYPE = (2 << 19), /* Normal directory */
> + DCACHE_AUTODIR_TYPE = (3 << 19), /* Lookupless directory (presumed automount) */
> + DCACHE_REGULAR_TYPE = (4 << 19), /* Regular file type */
> + DCACHE_SPECIAL_TYPE = (5 << 19), /* Other file type */
> + DCACHE_SYMLINK_TYPE = (6 << 19), /* Symlink */
> + DCACHE_NOKEY_NAME = BIT(22), /* Encrypted name encoded without key */
> + DCACHE_OP_REAL = BIT(23),
> + DCACHE_PAR_LOOKUP = BIT(24), /* being looked up (with parent locked shared) */
> + DCACHE_DENTRY_CURSOR = BIT(25),
> + DCACHE_NORCU = BIT(26), /* No RCU delay for freeing */
> +};
>
> -#define DCACHE_DISCONNECTED BIT(5)
> - /* This dentry is possibly not currently connected to the dcache tree, in
> - * which case its parent will either be itself, or will have this flag as
> - * well. nfsd will not use a dentry with this bit set, but will first
> - * endeavour to clear the bit either by discovering that it is connected,
> - * or by performing lookup operations. Any filesystem which supports
> - * nfsd_operations MUST have a lookup function which, if it finds a
> - * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
> - * dentry into place and return that dentry rather than the passed one,
> - * typically using d_splice_alias. */
> -
> -#define DCACHE_REFERENCED BIT(6) /* Recently used, don't discard. */
> -
> -#define DCACHE_DONTCACHE BIT(7) /* Purge from memory on final dput() */
> -
> -#define DCACHE_CANT_MOUNT BIT(8)
> -#define DCACHE_GENOCIDE BIT(9)
> -#define DCACHE_SHRINK_LIST BIT(10)
> -
> -#define DCACHE_OP_WEAK_REVALIDATE BIT(11)
> -
> -#define DCACHE_NFSFS_RENAMED BIT(12)
> - /* this dentry has been "silly renamed" and has to be deleted on the last
> - * dput() */
> -#define DCACHE_FSNOTIFY_PARENT_WATCHED BIT(13)
> - /* Parent inode is watched by some fsnotify listener */
> -
> -#define DCACHE_DENTRY_KILLED BIT(14)
> -
> -#define DCACHE_MOUNTED BIT(15) /* is a mountpoint */
> -#define DCACHE_NEED_AUTOMOUNT BIT(16) /* handle automount on this dir */
> -#define DCACHE_MANAGE_TRANSIT BIT(17) /* manage transit from this dirent */
> #define DCACHE_MANAGED_DENTRY \
> (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
>
> -#define DCACHE_LRU_LIST BIT(18)
> -
> -#define DCACHE_ENTRY_TYPE (7 << 19) /* bits 19..21 are for storing type: */
> -#define DCACHE_MISS_TYPE (0 << 19) /* Negative dentry */
> -#define DCACHE_WHITEOUT_TYPE (1 << 19) /* Whiteout dentry (stop pathwalk) */
> -#define DCACHE_DIRECTORY_TYPE (2 << 19) /* Normal directory */
> -#define DCACHE_AUTODIR_TYPE (3 << 19) /* Lookupless directory (presumed automount) */
> -#define DCACHE_REGULAR_TYPE (4 << 19) /* Regular file type */
> -#define DCACHE_SPECIAL_TYPE (5 << 19) /* Other file type */
> -#define DCACHE_SYMLINK_TYPE (6 << 19) /* Symlink */
> -
> -#define DCACHE_NOKEY_NAME BIT(22) /* Encrypted name encoded without key */
> -#define DCACHE_OP_REAL BIT(23)
> -
> -#define DCACHE_PAR_LOOKUP BIT(24) /* being looked up (with parent locked shared) */
> -#define DCACHE_DENTRY_CURSOR BIT(25)
> -#define DCACHE_NORCU BIT(26) /* No RCU delay for freeing */
> -
> extern seqlock_t rename_lock;
>
> /*
> --
> 2.49.0
>
