[CRIU] [PATCH v3 1/3] page-read: Do not lseek pages*img file during sequential reads

[Mike Rapoport]

From: Pavel Emelyanov <xemul at virtuozzo.com>

We keep track of current file position in page_read->pi_off_cur and we use
page_read->pi_off_next for seek operations. That way we only need to lseek
when the offsets do not match.

Signed-off-by: Pavel Emelyanov <xemul at virtuozzo.com>
Signed-off-by: Mike Rapoport <rppt at linux.vnet.ibm.com>
---
 criu/include/pagemap.h |  4 +++-
 criu/pagemap.c         | 24 +++++++++++++++---------
 test/zdtm.py           |  2 +-
 3 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/criu/include/pagemap.h b/criu/include/pagemap.h
index 39227f2..53b5375 100644
--- a/criu/include/pagemap.h
+++ b/criu/include/pagemap.h
@@ -63,7 +63,9 @@ struct page_read {
 					   go to this guy for page, see
 					   read_pagemap_page */
 	unsigned long cvaddr;		/* vaddr we are on */
-	off_t pi_off;			/* current offset in pages file */
+	off_t pi_off_cur;		/* current offset in pages file */
+	off_t pi_off_next;		/* offset to set in pages file after
+					   seek operations */
 
 	struct iovec bunch;		/* record consequent neighbour
 					   iovecs to punch together */
diff --git a/criu/pagemap.c b/criu/pagemap.c
index a2f4c85..69dc9ab 100644
--- a/criu/pagemap.c
+++ b/criu/pagemap.c
@@ -98,7 +98,8 @@ int dedup_one_iovec(struct page_read *pr, struct iovec *iov)
 		pagemap2iovec(pr->pe, &piov);
 		piov_end = (unsigned long)piov.iov_base + piov.iov_len;
 		if (!pagemap_in_parent(pr->pe)) {
-			ret = punch_hole(pr, pr->pi_off, min(piov_end, iov_end) - off, false);
+			ret = punch_hole(pr, pr->pi_off_cur,
+					 min(piov_end, iov_end) - off, false);
 			if (ret == -1)
 				return ret;
 		}
@@ -161,7 +162,7 @@ static void skip_pagemap_pages(struct page_read *pr, unsigned long len)
 
 	pr_debug("\tpr%u Skip %lu bytes from page-dump\n", pr->id, len);
 	if (pagemap_present(pr->pe))
-		pr->pi_off += len;
+		pr->pi_off_next += len;
 	pr->cvaddr += len;
 }
 
@@ -258,25 +259,28 @@ static int read_local_page(struct page_read *pr, unsigned long vaddr,
 			   unsigned long len, void *buf)
 {
 	int fd = img_raw_fd(pr->pi);
-	off_t current_vaddr = lseek(fd, pr->pi_off, SEEK_SET);
 	int ret;
 
-	pr_debug("\tpr%u Read page from self %lx/%"PRIx64"\n", pr->id, pr->cvaddr, current_vaddr);
+	if (pr->pi_off_cur != pr->pi_off_next)
+		pr->pi_off_cur = lseek(fd, pr->pi_off_next, SEEK_SET);
+
+	pr_debug("\tpr%u Read page from self %lx/%"PRIx64"\n", pr->id, pr->cvaddr, pr->pi_off_cur);
 	ret = read(fd, buf, len);
 	if (ret != len) {
 		pr_perror("Can't read mapping page %d", ret);
 		return -1;
 	}
 
-	pr->pi_off += len;
-
 	if (opts.auto_dedup) {
-		ret = punch_hole(pr, current_vaddr, len, false);
+		ret = punch_hole(pr, pr->pi_off_cur, len, false);
 		if (ret == -1) {
 			return -1;
 		}
 	}
 
+	pr->pi_off_cur += len;
+	pr->pi_off_next += len;
+
 	return 0;
 }
 
@@ -342,7 +346,8 @@ static void close_page_read(struct page_read *pr)
 static void reset_pagemap(struct page_read *pr)
 {
 	pr->cvaddr = 0;
-	pr->pi_off = 0;
+	pr->pi_off_cur = 0;
+	pr->pi_off_next = 0;
 	pr->curr_pme = -1;
 	pr->pe = NULL;
 
@@ -484,7 +489,8 @@ int open_page_read_at(int dfd, int pid, struct page_read *pr, int pr_flags)
 	pr->pe = NULL;
 	pr->parent = NULL;
 	pr->cvaddr = 0;
-	pr->pi_off = 0;
+	pr->pi_off_cur = 0;
+	pr->pi_off_next = 0;
 	pr->bunch.iov_len = 0;
 	pr->bunch.iov_base = NULL;
 	pr->pmes = NULL;
diff --git a/test/zdtm.py b/test/zdtm.py
index 0d8503f..e4ff1e3 100755
--- a/test/zdtm.py
+++ b/test/zdtm.py
@@ -517,7 +517,7 @@ class zdtm_test:
 			subprocess.check_call(["make", "zdtm_ct"])
 		if not os.access("zdtm/lib/libzdtmtst.a", os.F_OK):
 			subprocess.check_call(["make", "-C", "zdtm/"])
-		subprocess.check_call(["flock", "zdtm_mount_cgroups.lock", "./zdtm_mount_cgroups"])
+#		subprocess.check_call(["flock", "zdtm_mount_cgroups.lock", "./zdtm_mount_cgroups"])
 
 
 class inhfd_test:
-- 
1.9.1