| Message ID | 167391051810.2311931.8545361041888737395.stgit@warthog.procyon.org.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | iov_iter: Improve page extraction (ref, pin or just list) | expand |
On Mon, Jan 16, 2023 at 11:08:38PM +0000, David Howells wrote: > Change the ITER_SOURCE and ITER_DEST direction macros into an enum and > provide three new helper functions: > > iov_iter_dir() - returns the iterator direction > iov_iter_is_dest() - returns true if it's an ITER_DEST iterator > iov_iter_is_source() - returns true if it's an ITER_SOURCE iterator What for? We have two valid values - 1) it is a data source 2) it is not a data source Why do we need to store that as an enum?
Al Viro <viro@zeniv.linux.org.uk> wrote: > > Change the ITER_SOURCE and ITER_DEST direction macros into an enum and > > provide three new helper functions: > > > > iov_iter_dir() - returns the iterator direction > > iov_iter_is_dest() - returns true if it's an ITER_DEST iterator > > iov_iter_is_source() - returns true if it's an ITER_SOURCE iterator > > What for? We have two valid values - > 1) it is a data source > 2) it is not a data source > Why do we need to store that as an enum? Compile time type checking. David
On Wed, Jan 18, 2023 at 11:17:41PM +0000, David Howells wrote: > Al Viro <viro@zeniv.linux.org.uk> wrote: > > > > Change the ITER_SOURCE and ITER_DEST direction macros into an enum and > > > provide three new helper functions: > > > > > > iov_iter_dir() - returns the iterator direction > > > iov_iter_is_dest() - returns true if it's an ITER_DEST iterator > > > iov_iter_is_source() - returns true if it's an ITER_SOURCE iterator > > > > What for? We have two valid values - > > 1) it is a data source > > 2) it is not a data source > > Why do we need to store that as an enum? > > Compile time type checking. Huh? int-to-enum conversion is quiet; it would catch explicit huge constants, but that's it...
Al Viro <viro@zeniv.linux.org.uk> wrote: > > Compile time type checking. > > Huh? int-to-enum conversion is quiet; it would catch explicit > huge constants, but that's it... *shrug*. But can we at least get rid of the: iov_iter_foo(&iter, ITER_SOURCE, ...); WARN_ON(direction & ~(READ | WRITE)); mismatch? Either use ITER_SOURCE/DEST or use READ/WRITE but not mix them. David
diff --git a/include/linux/uio.h b/include/linux/uio.h index 365e26c405f2..8d0dabfcb2fe 100644 --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -29,8 +29,10 @@ enum iter_type { ITER_UBUF, }; -#define ITER_SOURCE 1 // == WRITE -#define ITER_DEST 0 // == READ +enum iter_dir { + ITER_DEST = 0, // == READ + ITER_SOURCE = 1, // == WRITE +} __mode(byte); struct iov_iter_state { size_t iov_offset; @@ -39,9 +41,9 @@ struct iov_iter_state { }; struct iov_iter { - u8 iter_type; + enum iter_type iter_type __mode(byte); bool nofault; - bool data_source; + enum iter_dir data_source; bool user_backed; union { size_t iov_offset; @@ -114,6 +116,26 @@ static inline bool iov_iter_is_xarray(const struct iov_iter *i) return iov_iter_type(i) == ITER_XARRAY; } +static inline enum iter_dir iov_iter_dir(const struct iov_iter *i) +{ + return i->data_source; +} + +static inline bool iov_iter_is_source(const struct iov_iter *i) +{ + return iov_iter_dir(i) == ITER_SOURCE; /* ie. WRITE */ +} + +static inline bool iov_iter_is_dest(const struct iov_iter *i) +{ + return iov_iter_dir(i) == ITER_DEST; /* ie. READ */ +} + +static inline bool iov_iter_dir_valid(enum iter_dir direction) +{ + return direction == ITER_DEST || direction == ITER_SOURCE; +} + static inline bool user_backed_iter(const struct iov_iter *i) { return i->user_backed;
Change the ITER_SOURCE and ITER_DEST direction macros into an enum and provide three new helper functions: iov_iter_dir() - returns the iterator direction iov_iter_is_dest() - returns true if it's an ITER_DEST iterator iov_iter_is_source() - returns true if it's an ITER_SOURCE iterator Signed-off-by: David Howells <dhowells@redhat.com> cc: Al Viro <viro@zeniv.linux.org.uk> Link: https://lore.kernel.org/r/167305161763.1521586.6593798818336440133.stgit@warthog.procyon.org.uk/ # v4 Link: https://lore.kernel.org/r/167344726413.2425628.317218805692680763.stgit@warthog.procyon.org.uk/ # v5 --- include/linux/uio.h | 30 ++++++++++++++++++++++++++---- 1 file changed, 26 insertions(+), 4 deletions(-)