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page-xfer: refactoring analyze_iov and fill_userbuf

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* handle unexpected errors of process_vm_readv
* adjust riovs in analyze_iov
* call handle_faulty_iov only if process_vm_readv returns EFAULT.

Signed-off-by: Andrei Vagin <avagin@gmail.com>
This commit is contained in:
Andrei Vagin 2022-04-28 19:09:07 +03:00
parent efeedf3912
commit f43dae720a
1 changed files with 29 additions and 38 deletions
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67
criu/page-xfer.c
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@ -617,31 +617,18 @@ static inline u32 ppb_xfer_flags(struct page_xfer *xfer, struct page_pipe_buf *p
*/
unsigned long handle_faulty_iov(int pid, struct iovec *riov, unsigned long faulty_index, struct iovec *bufvec,
struct iovec *aux_iov, unsigned long *aux_len, unsigned long partial_read_bytes)
struct iovec *aux_iov, unsigned long *aux_len)
{
struct iovec dummy;
ssize_t bytes_read;
unsigned long offset = 0;
unsigned long final_read_cnt = 0;
/* Handling Case 2*/
if (riov[faulty_index].iov_len == PAGE_SIZE) {
cnt_sub(CNT_PAGES_WRITTEN, 1);
return 0;
}
/* Handling Case 3-Part 3.2*/
offset = (partial_read_bytes) ? partial_read_bytes : PAGE_SIZE;
dummy.iov_base = riov[faulty_index].iov_base + offset;
dummy.iov_len = riov[faulty_index].iov_len - offset;
if (!partial_read_bytes)
cnt_sub(CNT_PAGES_WRITTEN, 1);
dummy.iov_base = riov[faulty_index].iov_base;
dummy.iov_len = riov[faulty_index].iov_len;
while (dummy.iov_len) {
bytes_read = process_vm_readv(pid, bufvec, 1, &dummy, 1, 0);
if (bytes_read == -1) {
/* Handling faulty page read in faulty iov */
cnt_sub(CNT_PAGES_WRITTEN, 1);
@ -671,14 +658,12 @@ unsigned long handle_faulty_iov(int pid, struct iovec *riov, unsigned long fault
/*
* This function will position start pointer to the latest
* successfully read iov in iovec. In case of partial read it
* returns partial_read_bytes, otherwise 0.
* successfully read iov in iovec.
*/
static unsigned long analyze_iov(ssize_t bytes_read, struct iovec *riov, unsigned long *index, struct iovec *aux_iov,
unsigned long *aux_len)
{
ssize_t processed_bytes = 0;
unsigned long partial_read_bytes = 0;
/* correlating iovs with read bytes */
while (processed_bytes < bytes_read) {
@ -692,13 +677,17 @@ static unsigned long analyze_iov(ssize_t bytes_read, struct iovec *riov, unsigne
/* handling partially processed faulty iov*/
if (processed_bytes - bytes_read) {
unsigned long partial_read_bytes = 0;
(*index) -= 1;
partial_read_bytes = riov[*index].iov_len - (processed_bytes - bytes_read);
aux_iov[*aux_len - 1].iov_len = partial_read_bytes;
riov[*index].iov_base += partial_read_bytes;
riov[*index].iov_len -= partial_read_bytes;
}
return partial_read_bytes;
return 0;
}
/*
@ -723,40 +712,36 @@ static long fill_userbuf(int pid, struct page_pipe_buf *ppb, struct iovec *bufve
ssize_t bytes_read;
unsigned long total_read = 0;
unsigned long start = 0;
unsigned long partial_read_bytes = 0;
while (start < ppb->nr_segs) {
bytes_read = process_vm_readv(pid, bufvec, 1, &riov[start], ppb->nr_segs - start, 0);
if (bytes_read == -1) {
if (errno == ESRCH) {
pr_debug("Target process PID:%d not found\n", pid);
return -ESRCH;
}
if (errno != EFAULT) {
pr_perror("process_vm_readv failed");
return -1;
}
/* Handling Case 1*/
if (riov[start].iov_len == PAGE_SIZE) {
cnt_sub(CNT_PAGES_WRITTEN, 1);
start += 1;
continue;
} else if (errno == ESRCH) {
pr_debug("Target process PID:%d not found\n", pid);
return -ESRCH;
}
total_read += handle_faulty_iov(pid, riov, start, bufvec, aux_iov, aux_len);
start += 1;
continue;
}
partial_read_bytes = 0;
if (bytes_read > 0) {
partial_read_bytes = analyze_iov(bytes_read, riov, &start, aux_iov, aux_len);
if (analyze_iov(bytes_read, riov, &start, aux_iov, aux_len) < 0)
return -1;
bufvec->iov_base += bytes_read;
bufvec->iov_len -= bytes_read;
total_read += bytes_read;
}
/*
* If all iovs not processed in one go,
* it means some iov in between has failed.
*/
if (start < ppb->nr_segs)
total_read += handle_faulty_iov(pid, riov, start, bufvec, aux_iov, aux_len, partial_read_bytes);
start += 1;
}
return total_read;
@ -817,7 +802,13 @@ int page_xfer_predump_pages(int pid, struct page_xfer *xfer, struct page_pipe *p
bufvec.iov_base = userbuf;
bytes_read = fill_userbuf(pid, ppb, &bufvec, aux_iov, &aux_len);
if (bytes_read == -ESRCH)
if (bytes_read == -ESRCH) {
timing_stop(TIME_MEMDUMP);
munmap(userbuf, userbuf_len);
xfree(aux_iov);
return 0;
}
if (bytes_read < 0)
goto err;
bufvec.iov_base = userbuf;