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new iov_iter flavour - ITER_UBUF

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Equivalent of single-segment iovec.  Initialized by iov_iter_ubuf(),
checked for by iter_is_ubuf(), otherwise behaves like ITER_IOVEC
ones.

We are going to expose the things like ->write_iter() et.al. to those
in subsequent commits.

New predicate (user_backed_iter()) that is true for ITER_IOVEC and
ITER_UBUF; places like direct-IO handling should use that for
checking that pages we modify after getting them from iov_iter_get_pages()
would need to be dirtied.

DO NOT assume that replacing iter_is_iovec() with user_backed_iter()
will solve all problems - there's code that uses iter_is_iovec() to
decide how to poke around in iov_iter guts and for that the predicate
replacement obviously won't suffice.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2022-05-22 14:59:25 -04:00
parent fa9db655d0
commit fcb14cb1bd
12 changed files with 108 additions and 31 deletions
Download Patch File Download Diff File Expand all files Collapse all files

26
include/linux/uio.h
View File

@@ -26,6 +26,7 @@ enum iter_type {
ITER_PIPE,
ITER_XARRAY,
ITER_DISCARD,
ITER_UBUF,
};
struct iov_iter_state {
@@ -38,6 +39,7 @@ struct iov_iter {
u8 iter_type;
bool nofault;
bool data_source;
bool user_backed;
size_t iov_offset;
size_t count;
union {
@@ -46,6 +48,7 @@ struct iov_iter {
const struct bio_vec *bvec;
struct xarray *xarray;
struct pipe_inode_info *pipe;
void __user *ubuf;
};
union {
unsigned long nr_segs;
@@ -70,6 +73,11 @@ static inline void iov_iter_save_state(struct iov_iter *iter,
state->nr_segs = iter->nr_segs;
}
static inline bool iter_is_ubuf(const struct iov_iter *i)
{
return iov_iter_type(i) == ITER_UBUF;
}
static inline bool iter_is_iovec(const struct iov_iter *i)
{
return iov_iter_type(i) == ITER_IOVEC;
@@ -105,6 +113,11 @@ static inline unsigned char iov_iter_rw(const struct iov_iter *i)
return i->data_source ? WRITE : READ;
}
static inline bool user_backed_iter(const struct iov_iter *i)
{
return i->user_backed;
}
/*
* Total number of bytes covered by an iovec.
*
@@ -322,4 +335,17 @@ ssize_t __import_iovec(int type, const struct iovec __user *uvec,
int import_single_range(int type, void __user *buf, size_t len,
struct iovec *iov, struct iov_iter *i);
static inline void iov_iter_ubuf(struct iov_iter *i, unsigned int direction,
void __user *buf, size_t count)
{
WARN_ON(direction & ~(READ | WRITE));
*i = (struct iov_iter) {
.iter_type = ITER_UBUF,
.user_backed = true,
.data_source = direction,
.ubuf = buf,
.count = count
};
}
#endif