mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-25 10:19:47 +00:00
iov_iter: add ITER_BVEC_FLAG_NO_REF flag
For ITER_BVEC, if we're holding on to kernel pages, the caller doesn't need to grab a reference to the bvec pages, and drop that same reference on IO completion. This is essentially safe for any ITER_BVEC, but some use cases end up reusing pages and uncondtionally dropping a page reference on completion. And example of that is sendfile(2), that ends up being a splice_in + splice_out on the pipe pages. Add a flag that tells us it's fine to not grab a page reference to the bvec pages, since that caller knows not to drop a reference when it's done with the pages. Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
parent
bf33a7699e
commit
875f1d0769
2 changed files with 22 additions and 5 deletions
|
@ -855,6 +855,9 @@ static int io_import_fixed(struct io_ring_ctx *ctx, int rw,
|
|||
iov_iter_bvec(iter, rw, imu->bvec, imu->nr_bvecs, offset + len);
|
||||
if (offset)
|
||||
iov_iter_advance(iter, offset);
|
||||
|
||||
/* don't drop a reference to these pages */
|
||||
iter->type |= ITER_BVEC_FLAG_NO_REF;
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
|
|
@ -23,14 +23,23 @@ struct kvec {
|
|||
};
|
||||
|
||||
enum iter_type {
|
||||
ITER_IOVEC = 0,
|
||||
ITER_KVEC = 2,
|
||||
ITER_BVEC = 4,
|
||||
ITER_PIPE = 8,
|
||||
ITER_DISCARD = 16,
|
||||
/* set if ITER_BVEC doesn't hold a bv_page ref */
|
||||
ITER_BVEC_FLAG_NO_REF = 2,
|
||||
|
||||
/* iter types */
|
||||
ITER_IOVEC = 4,
|
||||
ITER_KVEC = 8,
|
||||
ITER_BVEC = 16,
|
||||
ITER_PIPE = 32,
|
||||
ITER_DISCARD = 64,
|
||||
};
|
||||
|
||||
struct iov_iter {
|
||||
/*
|
||||
* Bit 0 is the read/write bit, set if we're writing.
|
||||
* Bit 1 is the BVEC_FLAG_NO_REF bit, set if type is a bvec and
|
||||
* the caller isn't expecting to drop a page reference when done.
|
||||
*/
|
||||
unsigned int type;
|
||||
size_t iov_offset;
|
||||
size_t count;
|
||||
|
@ -84,6 +93,11 @@ static inline unsigned char iov_iter_rw(const struct iov_iter *i)
|
|||
return i->type & (READ | WRITE);
|
||||
}
|
||||
|
||||
static inline bool iov_iter_bvec_no_ref(const struct iov_iter *i)
|
||||
{
|
||||
return (i->type & ITER_BVEC_FLAG_NO_REF) != 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* Total number of bytes covered by an iovec.
|
||||
*
|
||||
|
|
Loading…
Reference in a new issue