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new iov_iter flavour - ITER_UBUF 

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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
block/fops.c
View File

@ -75,7 +75,7 @@ static ssize_t __blkdev_direct_IO_simple(struct kiocb *iocb,
if (iov_iter_rw(iter) == READ) {
bio_init(&bio, bdev, vecs, nr_pages, REQ_OP_READ);
if (iter_is_iovec(iter))
if (user_backed_iter(iter))
should_dirty = true;
} else {
bio_init(&bio, bdev, vecs, nr_pages, dio_bio_write_op(iocb));
@ -204,7 +204,7 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
}
dio->size = 0;
if (is_read && iter_is_iovec(iter))
if (is_read && user_backed_iter(iter))
dio->flags |= DIO_SHOULD_DIRTY;
blk_start_plug(&plug);
@ -335,7 +335,7 @@ static ssize_t __blkdev_direct_IO_async(struct kiocb *iocb,
dio->size = bio->bi_iter.bi_size;
if (is_read) {
if (iter_is_iovec(iter)) {
if (user_backed_iter(iter)) {
dio->flags |= DIO_SHOULD_DIRTY;
bio_set_pages_dirty(bio);
}

2
fs/ceph/file.c
View File

@ -1262,7 +1262,7 @@ ceph_direct_read_write(struct kiocb *iocb, struct iov_iter *iter,
size_t count = iov_iter_count(iter);
loff_t pos = iocb->ki_pos;
bool write = iov_iter_rw(iter) == WRITE;
bool should_dirty = !write && iter_is_iovec(iter);
bool should_dirty = !write && user_backed_iter(iter);
if (write && ceph_snap(file_inode(file)) != CEPH_NOSNAP)
return -EROFS;

2
fs/cifs/file.c
View File

@ -4004,7 +4004,7 @@ static ssize_t __cifs_readv(
if (!is_sync_kiocb(iocb))
ctx->iocb = iocb;
if (iter_is_iovec(to))
if (user_backed_iter(to))
ctx->should_dirty = true;
if (direct) {

2
fs/direct-io.c
View File

@ -1251,7 +1251,7 @@ ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
spin_lock_init(&dio->bio_lock);
dio->refcount = 1;
dio->should_dirty = iter_is_iovec(iter) && iov_iter_rw(iter) == READ;
dio->should_dirty = user_backed_iter(iter) && iov_iter_rw(iter) == READ;
sdio.iter = iter;
sdio.final_block_in_request = end >> blkbits;

4
fs/fuse/dev.c
View File

@ -1356,7 +1356,7 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, struct iov_iter *to)
if (!fud)
return -EPERM;
if (!iter_is_iovec(to))
if (!user_backed_iter(to))
return -EINVAL;
fuse_copy_init(&cs, 1, to);
@ -1949,7 +1949,7 @@ static ssize_t fuse_dev_write(struct kiocb *iocb, struct iov_iter *from)
if (!fud)
return -EPERM;
if (!iter_is_iovec(from))
if (!user_backed_iter(from))
return -EINVAL;
fuse_copy_init(&cs, 0, from);

2
fs/fuse/file.c
View File

@ -1465,7 +1465,7 @@ ssize_t fuse_direct_io(struct fuse_io_priv *io, struct iov_iter *iter,
inode_unlock(inode);
}
io->should_dirty = !write && iter_is_iovec(iter);
io->should_dirty = !write && user_backed_iter(iter);
while (count) {
ssize_t nres;
fl_owner_t owner = current->files;

2
fs/gfs2/file.c
View File

@ -780,7 +780,7 @@ static inline bool should_fault_in_pages(struct iov_iter *i,
if (!count)
return false;
if (!iter_is_iovec(i))
if (!user_backed_iter(i))
return false;
size = PAGE_SIZE;

2
fs/iomap/direct-io.c
View File

@ -533,7 +533,7 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
iomi.flags |= IOMAP_NOWAIT;
}
if (iter_is_iovec(iter))
if (user_backed_iter(iter))
dio->flags |= IOMAP_DIO_DIRTY;
} else {
iomi.flags |= IOMAP_WRITE;

2
fs/nfs/direct.c
View File

@ -478,7 +478,7 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter,
if (!is_sync_kiocb(iocb))
dreq->iocb = iocb;
if (iter_is_iovec(iter))
if (user_backed_iter(iter))
dreq->flags = NFS_ODIRECT_SHOULD_DIRTY;
if (!swap)

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

87
lib/iov_iter.c
View File

@ -16,6 +16,16 @@
#define PIPE_PARANOIA /* for now */
/* covers ubuf and kbuf alike */
#define iterate_buf(i, n, base, len, off, __p, STEP) { \
size_t __maybe_unused off = 0; \
len = n; \
base = __p + i->iov_offset; \
len -= (STEP); \
i->iov_offset += len; \
n = len; \
}
/* covers iovec and kvec alike */
#define iterate_iovec(i, n, base, len, off, __p, STEP) { \
size_t off = 0; \
@ -110,7 +120,12 @@ __out: \
if (unlikely(i->count < n)) \
n = i->count; \
if (likely(n)) { \
if (likely(iter_is_iovec(i))) { \
if (likely(iter_is_ubuf(i))) { \
void __user *base; \
size_t len; \
iterate_buf(i, n, base, len, off, \
i->ubuf, (I)) \
} else if (likely(iter_is_iovec(i))) { \
const struct iovec *iov = i->iov; \
void __user *base; \
size_t len; \
@ -275,7 +290,11 @@ out:
*/
size_t fault_in_iov_iter_readable(const struct iov_iter *i, size_t size)
{
if (iter_is_iovec(i)) {
if (iter_is_ubuf(i)) {
size_t n = min(size, iov_iter_count(i));
n -= fault_in_readable(i->ubuf + i->iov_offset, n);
return size - n;
} else if (iter_is_iovec(i)) {
size_t count = min(size, iov_iter_count(i));
const struct iovec *p;
size_t skip;
@ -314,7 +333,11 @@ EXPORT_SYMBOL(fault_in_iov_iter_readable);
*/
size_t fault_in_iov_iter_writeable(const struct iov_iter *i, size_t size)
{
if (iter_is_iovec(i)) {
if (iter_is_ubuf(i)) {
size_t n = min(size, iov_iter_count(i));
n -= fault_in_safe_writeable(i->ubuf + i->iov_offset, n);
return size - n;
} else if (iter_is_iovec(i)) {
size_t count = min(size, iov_iter_count(i));
const struct iovec *p;
size_t skip;
@ -345,6 +368,7 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction,
*i = (struct iov_iter) {
.iter_type = ITER_IOVEC,
.nofault = false,
.user_backed = true,
.data_source = direction,
.iov = iov,
.nr_segs = nr_segs,
@ -494,7 +518,7 @@ size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
{
if (unlikely(iov_iter_is_pipe(i)))
return copy_pipe_to_iter(addr, bytes, i);
if (iter_is_iovec(i))
if (user_backed_iter(i))
might_fault();
iterate_and_advance(i, bytes, base, len, off,
copyout(base, addr + off, len),
@ -583,7 +607,7 @@ size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
{
if (unlikely(iov_iter_is_pipe(i)))
return copy_mc_pipe_to_iter(addr, bytes, i);
if (iter_is_iovec(i))
if (user_backed_iter(i))
might_fault();
__iterate_and_advance(i, bytes, base, len, off,
copyout_mc(base, addr + off, len),
@ -601,7 +625,7 @@ size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
WARN_ON(1);
return 0;
}
if (iter_is_iovec(i))
if (user_backed_iter(i))
might_fault();
iterate_and_advance(i, bytes, base, len, off,
copyin(addr + off, base, len),
@ -894,16 +918,16 @@ void iov_iter_advance(struct iov_iter *i, size_t size)
{
if (unlikely(i->count < size))
size = i->count;
if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) {
if (likely(iter_is_ubuf(i)) || unlikely(iov_iter_is_xarray(i))) {
i->iov_offset += size;
i->count -= size;
} else if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) {
/* iovec and kvec have identical layouts */
iov_iter_iovec_advance(i, size);
} else if (iov_iter_is_bvec(i)) {
iov_iter_bvec_advance(i, size);
} else if (iov_iter_is_pipe(i)) {
pipe_advance(i, size);
} else if (unlikely(iov_iter_is_xarray(i))) {
i->iov_offset += size;
i->count -= size;
} else if (iov_iter_is_discard(i)) {
i->count -= size;
}
@ -950,7 +974,7 @@ void iov_iter_revert(struct iov_iter *i, size_t unroll)
return;
}
unroll -= i->iov_offset;
if (iov_iter_is_xarray(i)) {
if (iov_iter_is_xarray(i) || iter_is_ubuf(i)) {
BUG(); /* We should never go beyond the start of the specified
* range since we might then be straying into pages that
* aren't pinned.
@ -1158,6 +1182,14 @@ static bool iov_iter_aligned_bvec(const struct iov_iter *i, unsigned addr_mask,
bool iov_iter_is_aligned(const struct iov_iter *i, unsigned addr_mask,
unsigned len_mask)
{
if (likely(iter_is_ubuf(i))) {
if (i->count & len_mask)
return false;
if ((unsigned long)(i->ubuf + i->iov_offset) & addr_mask)
return false;
return true;
}
if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
return iov_iter_aligned_iovec(i, addr_mask, len_mask);
@ -1233,6 +1265,13 @@ static unsigned long iov_iter_alignment_bvec(const struct iov_iter *i)
unsigned long iov_iter_alignment(const struct iov_iter *i)
{
if (likely(iter_is_ubuf(i))) {
size_t size = i->count;
if (size)
return ((unsigned long)i->ubuf + i->iov_offset) | size;
return 0;
}
/* iovec and kvec have identical layouts */
if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
return iov_iter_alignment_iovec(i);
@ -1263,6 +1302,9 @@ unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
size_t size = i->count;
unsigned k;
if (iter_is_ubuf(i))
return 0;
if (WARN_ON(!iter_is_iovec(i)))
return ~0U;
@ -1385,12 +1427,15 @@ static ssize_t iter_xarray_get_pages(struct iov_iter *i,
return min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
}
/* must be done on non-empty ITER_IOVEC one */
/* must be done on non-empty ITER_UBUF or ITER_IOVEC one */
static unsigned long first_iovec_segment(const struct iov_iter *i, size_t *size)
{
size_t skip;
long k;
if (iter_is_ubuf(i))
return (unsigned long)i->ubuf + i->iov_offset;
for (k = 0, skip = i->iov_offset; k < i->nr_segs; k++, skip = 0) {
size_t len = i->iov[k].iov_len - skip;
@ -1432,7 +1477,7 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
if (maxsize > MAX_RW_COUNT)
maxsize = MAX_RW_COUNT;
if (likely(iter_is_iovec(i))) {
if (likely(user_backed_iter(i))) {
unsigned int gup_flags = 0;
unsigned long addr;
@ -1559,7 +1604,7 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
if (maxsize > MAX_RW_COUNT)
maxsize = MAX_RW_COUNT;
if (likely(iter_is_iovec(i))) {
if (likely(user_backed_iter(i))) {
unsigned int gup_flags = 0;
unsigned long addr;
@ -1715,6 +1760,11 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages)
{
if (unlikely(!i->count))
return 0;
if (likely(iter_is_ubuf(i))) {
unsigned offs = offset_in_page(i->ubuf + i->iov_offset);
int npages = DIV_ROUND_UP(offs + i->count, PAGE_SIZE);
return min(npages, maxpages);
}
/* iovec and kvec have identical layouts */
if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
return iov_npages(i, maxpages);
@ -1749,17 +1799,16 @@ const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
WARN_ON(1);
return NULL;
}
if (unlikely(iov_iter_is_discard(new) || iov_iter_is_xarray(new)))
return NULL;
if (iov_iter_is_bvec(new))
return new->bvec = kmemdup(new->bvec,
new->nr_segs * sizeof(struct bio_vec),
flags);
else
else if (iov_iter_is_kvec(new) || iter_is_iovec(new))
/* iovec and kvec have identical layout */
return new->iov = kmemdup(new->iov,
new->nr_segs * sizeof(struct iovec),
flags);
return NULL;
}
EXPORT_SYMBOL(dup_iter);
@ -1953,10 +2002,12 @@ EXPORT_SYMBOL(import_single_range);
void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state)
{
if (WARN_ON_ONCE(!iov_iter_is_bvec(i) && !iter_is_iovec(i)) &&
!iov_iter_is_kvec(i))
!iov_iter_is_kvec(i) && !iter_is_ubuf(i))
return;
i->iov_offset = state->iov_offset;
i->count = state->count;
if (iter_is_ubuf(i))
return;
/*
* For the *vec iters, nr_segs + iov is constant - if we increment
* the vec, then we also decrement the nr_segs count. Hence we don't

2
mm/shmem.c
View File

@ -2602,7 +2602,7 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
ret = copy_page_to_iter(page, offset, nr, to);
put_page(page);
} else if (iter_is_iovec(to)) {
} else if (user_backed_iter(to)) {
/*
* Copy to user tends to be so well optimized, but
* clear_user() not so much, that it is noticeably