| Message ID | 20171215171012.GA11918@bombadil.infradead.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 12/15/2017 09:10 AM, Matthew Wilcox wrote: > On Mon, Dec 11, 2017 at 03:10:22PM -0800, Randy Dunlap wrote: >>> +The XArray does not support storing :c:func:`IS_ERR` pointers; some >>> +conflict with data values and others conflict with entries the XArray >>> +uses for its own purposes. If you need to store special values which >>> +cannot be confused with real kernel pointers, the values 4, 8, ... 4092 >>> +are available. >> >> or if I know that they values are errno-range values, I can just shift them >> left by 2 to store them and then shift them right by 2 to use them? > > On further thought, I like this idea so much, it's worth writing helpers > for this usage. And test-suite (also doubles as a demonstration of how > to use it). > > diff --git a/include/linux/xarray.h b/include/linux/xarray.h > index c616e9319c7c..53aa251df57a 100644 > --- a/include/linux/xarray.h > +++ b/include/linux/xarray.h > @@ -232,6 +232,39 @@ static inline bool xa_is_value(const void *entry) > return (unsigned long)entry & 1; > } > > +/** > + * xa_mk_errno() - Create an XArray entry from an error number. > + * @error: Error number to store in XArray. > + * > + * Return: An entry suitable for storing in the XArray. > + */ > +static inline void *xa_mk_errno(long error) > +{ > + return (void *)(error << 2); > +} > + > +/** > + * xa_to_errno() - Get error number stored in an XArray entry. > + * @entry: XArray entry. > + * > + * Return: The error number stored in the XArray entry. > + */ > +static inline unsigned long xa_to_errno(const void *entry) > +{ > + return (long)entry >> 2; > +} > + > +/** > + * xa_is_errno() - Determine if an entry is an errno. > + * @entry: XArray entry. > + * > + * Return: True if the entry is an errno, false if it is a pointer. > + */ > +static inline bool xa_is_errno(const void *entry) > +{ > + return (((unsigned long)entry & 3) == 0) && (entry > (void *)-4096); Some named mask bits would be ^^^ preferable there. #define MAX_ERRNO 4095 // from err.h && (entry >= (void *)-MAX_ERRNO); > +} > + > /** > * xa_is_internal() - Is the entry an internal entry? > * @entry: Entry retrieved from the XArray > diff --git a/tools/testing/radix-tree/xarray-test.c b/tools/testing/radix-tree/xarray-test.c > index 43111786ebdd..b843cedf3988 100644 > --- a/tools/testing/radix-tree/xarray-test.c > +++ b/tools/testing/radix-tree/xarray-test.c > @@ -29,7 +29,13 @@ void check_xa_err(struct xarray *xa) > assert(xa_err(xa_store(xa, 1, xa_mk_value(0), GFP_KERNEL)) == 0); > assert(xa_err(xa_store(xa, 1, NULL, 0)) == 0); > // kills the test-suite :-( > -// assert(xa_err(xa_store(xa, 0, xa_mk_internal(0), 0)) == -EINVAL); > +// assert(xa_err(xa_store(xa, 0, xa_mk_internal(0), 0)) == -EINVAL); > + > + assert(xa_err(xa_store(xa, 0, xa_mk_errno(-ENOMEM), GFP_KERNEL)) == 0); > + assert(xa_err(xa_load(xa, 0)) == 0); > + assert(xa_is_errno(xa_load(xa, 0)) == true); > + assert(xa_to_errno(xa_load(xa, 0)) == -ENOMEM); > + xa_erase(xa, 0); > } > > void check_xa_tag(struct xarray *xa) > Thanks,
diff --git a/include/linux/xarray.h b/include/linux/xarray.h index c616e9319c7c..53aa251df57a 100644 --- a/include/linux/xarray.h +++ b/include/linux/xarray.h @@ -232,6 +232,39 @@ static inline bool xa_is_value(const void *entry) return (unsigned long)entry & 1; } +/** + * xa_mk_errno() - Create an XArray entry from an error number. + * @error: Error number to store in XArray. + * + * Return: An entry suitable for storing in the XArray. + */ +static inline void *xa_mk_errno(long error) +{ + return (void *)(error << 2); +} + +/** + * xa_to_errno() - Get error number stored in an XArray entry. + * @entry: XArray entry. + * + * Return: The error number stored in the XArray entry. + */ +static inline unsigned long xa_to_errno(const void *entry) +{ + return (long)entry >> 2; +} + +/** + * xa_is_errno() - Determine if an entry is an errno. + * @entry: XArray entry. + * + * Return: True if the entry is an errno, false if it is a pointer. + */ +static inline bool xa_is_errno(const void *entry) +{ + return (((unsigned long)entry & 3) == 0) && (entry > (void *)-4096); +} + /** * xa_is_internal() - Is the entry an internal entry? * @entry: Entry retrieved from the XArray diff --git a/tools/testing/radix-tree/xarray-test.c b/tools/testing/radix-tree/xarray-test.c index 43111786ebdd..b843cedf3988 100644 --- a/tools/testing/radix-tree/xarray-test.c +++ b/tools/testing/radix-tree/xarray-test.c @@ -29,7 +29,13 @@ void check_xa_err(struct xarray *xa) assert(xa_err(xa_store(xa, 1, xa_mk_value(0), GFP_KERNEL)) == 0); assert(xa_err(xa_store(xa, 1, NULL, 0)) == 0); // kills the test-suite :-( -// assert(xa_err(xa_store(xa, 0, xa_mk_internal(0), 0)) == -EINVAL); +// assert(xa_err(xa_store(xa, 0, xa_mk_internal(0), 0)) == -EINVAL); + + assert(xa_err(xa_store(xa, 0, xa_mk_errno(-ENOMEM), GFP_KERNEL)) == 0); + assert(xa_err(xa_load(xa, 0)) == 0); + assert(xa_is_errno(xa_load(xa, 0)) == true); + assert(xa_to_errno(xa_load(xa, 0)) == -ENOMEM); + xa_erase(xa, 0); } void check_xa_tag(struct xarray *xa)