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vdisk_fileio, async mode: Switch from kvec to bvec

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fileio_exec_async() for fileio devices with o_direct flag triggers
the following Linux direct_io datapath:
- fileio_exec_async()      -- ... --> iomap_dio_bio_actor()
- iomap_dio_bio_actor()    -- ... --> bio_iov_iter_get_pages()
- bio_iov_iter_get_pages() -- ... --> iov_iter_get_pages()
- iov_iter_get_pages() returns -EFAULT

iov_iter_get_pages() only handles iovec and bvec iterators.
Its kvec hanlding always return -EFAULT.

We cannot use iovec because calling iov_iter_init() from
the kernel context initializes iov_iter as ITER_KVEC.

Thus, use bvecs for fileio async direct IO.

Reported-by: Lu Chang
This commit is contained in:
Chesnokov Gleb
2021-12-08 21:44:58 +03:00
committed by Gleb Chesnokov
parent 9d7cf27c7c
commit 33b872d055
1 changed files with 28 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files
scst/src/dev_handlers/scst_vdisk.c
+28 -21
View File
@@ -267,8 +267,8 @@ struct vdisk_cmd_params {
} sync;
struct {
struct kiocb iocb;
struct kvec *kvec;
struct kvec small_kvec[4];
struct bio_vec *bvec;
struct bio_vec small_bvec[4];
} async;
};
struct scst_cmd *cmd;
@@ -3170,21 +3170,21 @@ static bool do_fileio_async(const struct vdisk_cmd_params *p)
}
}
static bool vdisk_alloc_async_kvec(struct scst_cmd *cmd,
static bool vdisk_alloc_async_bvec(struct scst_cmd *cmd,
struct vdisk_cmd_params *p)
{
int n;
n = scst_get_buf_count(cmd);
if (n <= ARRAY_SIZE(p->async.small_kvec)) {
p->async.kvec = &p->async.small_kvec[0];
if (n <= ARRAY_SIZE(p->async.small_bvec)) {
p->async.bvec = &p->async.small_bvec[0];
return true;
}
p->async.kvec = kmalloc_array(n, sizeof(*p->async.kvec),
p->async.bvec = kmalloc_array(n, sizeof(*p->async.bvec),
cmd->cmd_gfp_mask);
if (p->async.kvec == NULL) {
PRINT_ERROR("Unable to allocate kvec (%d)", n);
if (p->async.bvec == NULL) {
PRINT_ERROR("Unable to allocate bvec (%d)", n);
return false;
}
@@ -3235,10 +3235,10 @@ static enum compl_status_e fileio_exec_async(struct vdisk_cmd_params *p)
struct file *fd = virt_dev->fd;
struct iov_iter iter = { };
ssize_t length, total = 0;
struct kvec *kvec;
struct bio_vec *bvec;
struct page *page;
struct kiocb *iocb = &p->async.iocb;
uint8_t *address;
int sg_cnt = 0, dir, ret;
int offset, sg_cnt = 0, dir, ret;
switch (cmd->data_direction) {
case SCST_DATA_READ:
@@ -3252,28 +3252,35 @@ static enum compl_status_e fileio_exec_async(struct vdisk_cmd_params *p)
return CMD_FAILED;
}
if (!vdisk_alloc_async_kvec(cmd, p)) {
if (!vdisk_alloc_async_bvec(cmd, p)) {
scst_set_busy(cmd);
return CMD_SUCCEEDED;
}
p->execute_async = true;
kvec = p->async.kvec;
length = scst_get_buf_first(cmd, &address);
bvec = p->async.bvec;
length = scst_get_sg_page_first(cmd, &page, &offset);
while (length) {
*kvec++ = (struct kvec){
.iov_base = address,
.iov_len = length,
*bvec++ = (struct bio_vec){
.bv_page = page,
.bv_offset = offset,
.bv_len = length,
};
total += length;
sg_cnt++;
length = scst_get_buf_next(cmd, &address);
length = scst_get_sg_page_next(cmd, &page, &offset);
}
WARN_ON_ONCE(sg_cnt != cmd->sg_cnt);
iov_iter_kvec(&iter, dir, p->async.kvec, sg_cnt, total);
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 20, 0) || \
(defined(RHEL_RELEASE_CODE) && \
RHEL_RELEASE_CODE -0 >= RHEL_RELEASE_VERSION(8, 2))
iov_iter_bvec(&iter, dir, p->async.bvec, sg_cnt, total);
#else
iov_iter_bvec(&iter, ITER_BVEC | dir, p->async.bvec, sg_cnt, total);
#endif
*iocb = (struct kiocb) {
.ki_pos = p->loff,
.ki_filp = fd,
@@ -3295,8 +3302,8 @@ static enum compl_status_e fileio_exec_async(struct vdisk_cmd_params *p)
else
break;
}
if (p->async.kvec != p->async.small_kvec)
kfree(p->async.kvec);
if (p->async.bvec != p->async.small_bvec)
kfree(p->async.bvec);
if (ret != -EIOCBQUEUED) {
#if LINUX_VERSION_CODE < KERNEL_VERSION(5, 16, 0)
fileio_async_complete(iocb, ret, 0);