On Fri, Jun 30, 2023 at 01:48:49PM -0400, Chuck Lever wrote:
> From: Chuck Lever <chuck.lever@xxxxxxxxxx>
>
> Create a vector of directory operations in fs/libfs.c that handles
> directory seeks and readdir via stable offsets instead of the
> current cursor-based mechanism.
>
> For the moment these are unused.
>
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
> Documentation/filesystems/locking.rst | 2
> Documentation/filesystems/vfs.rst | 6 +
> fs/libfs.c | 247 +++++++++++++++++++++++++++++++++
> include/linux/fs.h | 18 ++
> 4 files changed, 272 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst
> index ed148919e11a..6a928fee3400 100644
> --- a/Documentation/filesystems/locking.rst
> +++ b/Documentation/filesystems/locking.rst
> @@ -85,6 +85,7 @@ prototypes::
> struct dentry *dentry, struct fileattr *fa);
> int (*fileattr_get)(struct dentry *dentry, struct fileattr *fa);
> struct posix_acl * (*get_acl)(struct mnt_idmap *, struct dentry *, int);
> + struct offset_ctx *(*get_offset_ctx)(struct inode *inode);
>
> locking rules:
> all may block
> @@ -115,6 +116,7 @@ atomic_open: shared (exclusive if O_CREAT is set in open flags)
> tmpfile: no
> fileattr_get: no or exclusive
> fileattr_set: exclusive
> +get_offset_ctx: no
> ============== =============================================
>
>
> diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst
> index cb2a97e49872..898d0b43109e 100644
> --- a/Documentation/filesystems/vfs.rst
> +++ b/Documentation/filesystems/vfs.rst
> @@ -515,6 +515,7 @@ As of kernel 2.6.22, the following members are defined:
> int (*fileattr_set)(struct mnt_idmap *idmap,
> struct dentry *dentry, struct fileattr *fa);
> int (*fileattr_get)(struct dentry *dentry, struct fileattr *fa);
> + struct offset_ctx *(*get_offset_ctx)(struct inode *inode);
> };
>
> Again, all methods are called without any locks being held, unless
> @@ -675,7 +676,10 @@ otherwise noted.
> called on ioctl(FS_IOC_SETFLAGS) and ioctl(FS_IOC_FSSETXATTR) to
> change miscellaneous file flags and attributes. Callers hold
> i_rwsem exclusive. If unset, then fall back to f_op->ioctl().
> -
> +``get_offset_ctx``
> + called to get the offset context for a directory inode. A
> + filesystem must define this operation to use
> + simple_offset_dir_operations.
>
> The Address Space Object
> ========================
> diff --git a/fs/libfs.c b/fs/libfs.c
> index 5b851315eeed..68b0000dc518 100644
> --- a/fs/libfs.c
> +++ b/fs/libfs.c
> @@ -239,6 +239,253 @@ const struct inode_operations simple_dir_inode_operations = {
> };
> EXPORT_SYMBOL(simple_dir_inode_operations);
>
> +static void offset_set(struct dentry *dentry, unsigned long offset)
> +{
> + dentry->d_fsdata = (void *)offset;
> +}
> +
> +static unsigned long dentry2offset(struct dentry *dentry)
> +{
> + return (unsigned long)dentry->d_fsdata;
> +}
This looks fine to me and tmpfs xfstests seem happy too. Currently we
use unsigned long in some places, and u32 in some other places. It's not
a big deal but I would prefer if we kept this consistent and made it
clear everywhere that the offset is a 32 bit unsigned and that the
xarray's limit is U32_MAX. So I would like to fold the following change
into this series unless there are objections:
diff --git a/fs/libfs.c b/fs/libfs.c
index 68b0000dc518..a7e56baf8bbd 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -239,14 +239,14 @@ const struct inode_operations simple_dir_inode_operations = {
};
EXPORT_SYMBOL(simple_dir_inode_operations);
-static void offset_set(struct dentry *dentry, unsigned long offset)
+static void offset_set(struct dentry *dentry, u32 offset)
{
- dentry->d_fsdata = (void *)offset;
+ dentry->d_fsdata = (void *)((uintptr_t)(offset));
}
-static unsigned long dentry2offset(struct dentry *dentry)
+static u32 dentry2offset(struct dentry *dentry)
{
- return (unsigned long)dentry->d_fsdata;
+ return (u32)((uintptr_t)(dentry->d_fsdata));
}
/**
@@ -296,12 +296,13 @@ int simple_offset_add(struct offset_ctx *octx, struct dentry *dentry)
*/
void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry)
{
- unsigned long index = dentry2offset(dentry);
+ u32 offset;
- if (index == 0)
+ offset = dentry2offset(dentry);
+ if (offset == 0)
return;
- xa_erase(&octx->xa, index);
+ xa_erase(&octx->xa, offset);
offset_set(dentry, 0);
}
@@ -322,8 +323,8 @@ int simple_offset_rename_exchange(struct inode *old_dir,
{
struct offset_ctx *old_ctx = old_dir->i_op->get_offset_ctx(old_dir);
struct offset_ctx *new_ctx = new_dir->i_op->get_offset_ctx(new_dir);
- unsigned long old_index = dentry2offset(old_dentry);
- unsigned long new_index = dentry2offset(new_dentry);
+ u32 old_index = dentry2offset(old_dentry);
+ u32 new_index = dentry2offset(new_dentry);
int ret;
simple_offset_remove(old_ctx, old_dentry);
@@ -414,7 +415,7 @@ static struct dentry *offset_find_next(struct xa_state *xas)
static bool offset_dir_emit(struct dir_context *ctx, struct dentry *dentry)
{
- loff_t offset = dentry2offset(dentry);
+ u32 offset = dentry2offset(dentry);
struct inode *inode = d_inode(dentry);
return ctx->actor(ctx, dentry->d_name.name, dentry->d_name.len, offset,
