On Thu, Apr 20, 2023 at 8:00 PM <crash-utility-request@xxxxxxxxxx> wrote:
Date: Thu, 20 Apr 2023 18:25:22 +0800
From: Tao Liu <ltao@xxxxxxxxxx>
To: crash-utility@xxxxxxxxxx
Subject: [Crash-utility] [PATCH v2] Replace lseek/read into pread for
kcore and vmcore reading.
Message-ID: <20230420102521.33698-1-ltao@xxxxxxxxxx>
Content-Type: text/plain; charset="US-ASCII"; x-default=true
Previously crash use lseek/read for kcore and vmcore reading, this involves 2
syscalls. And we can replace them with pread, only 1 syscall is needed for
kcore/vmcore reading, and we can have a better performance. Please note there
are plenty of places in crash using lseek/read, this patch doesn't modify all
of them, just the most commonly used kcore and diskdump vmcore reading.
Signed-off-by: Tao Liu <ltao@xxxxxxxxxx>
---
v1 -> v2: add offset check before pread.
---
diskdump.c | 31 +++++++++++++++++++++++++------
netdump.c | 19 ++++++++++++++-----
2 files changed, 39 insertions(+), 11 deletions(-)
diff --git a/diskdump.c b/diskdump.c
index cf5f5d9..6ecd08a 100644
--- a/diskdump.c
+++ b/diskdump.c
@@ -515,16 +515,24 @@ arm_kdump_header_adjust(int header_version)
static int
read_pd(int fd, off_t offset, page_desc_t *pd)
{
- const off_t failed = (off_t)-1;
+ int ret;
if (FLAT_FORMAT()) {
if (!read_flattened_format(fd, offset, pd, sizeof(*pd)))
return READ_ERROR;
} else {
- if (lseek(fd, offset, SEEK_SET) == failed)
+ if (offset < 0) {
+ if (CRASHDEBUG(8)) {
+ fprintf(fp, "read_pd: invalid offset: %lx\n", offset);
+ }
return SEEK_ERROR;
- if (read(fd, pd, sizeof(*pd)) != sizeof(*pd))
+ }
+ if ((ret = pread(fd, pd, sizeof(*pd), offset)) != sizeof(*pd)) {
+ if (ret == -1 && CRASHDEBUG(8)) {
+ fprintf(fp, "read_pd: pread error: %s\n", strerror(errno));
+ }
return READ_ERROR;
+ }
}
return 0;
@@ -1125,7 +1133,6 @@ cache_page(physaddr_t paddr)
off_t seek_offset;
page_desc_t pd;
const int block_size = dd->block_size;
- const off_t failed = (off_t)-1;
ulong retlen;
#ifdef ZSTD
static ZSTD_DCtx *dctx = NULL;
@@ -1190,10 +1197,22 @@ cache_page(physaddr_t paddr)
return PAGE_INCOMPLETE;
}
} else {
- if (lseek(dd->dfd, pd.offset, SEEK_SET) == failed)
+ if (pd.offset < 0) {
+ if (CRASHDEBUG(8)) {
+ fprintf(fp,
+ "read_diskdump/cache_page: "
+ "invalid offset: %lx\n", pd.offset);
+ }
return SEEK_ERROR;
- if (read(dd->dfd, dd->compressed_page, pd.size) != pd.size)
+ }
+ if ((ret = pread(dd->dfd, dd->compressed_page, pd.size, pd.offset)) != pd.size) {
+ if (ret == -1 && CRASHDEBUG(8)) {
+ fprintf(fp,
+ "read_diskdump/cache_page: "
+ "pread error: %s\n", strerror(errno));
+ }
return READ_ERROR;
+ }
}
if (pd.flags & DUMP_DH_COMPRESSED_ZLIB) {
diff --git a/netdump.c b/netdump.c
index 01af145..696f5fd 100644
--- a/netdump.c
+++ b/netdump.c
@@ -4336,7 +4336,7 @@ no_nt_prstatus_exists:
int
read_proc_kcore(int fd, void *bufptr, int cnt, ulong addr, physaddr_t paddr)
{
- int i;
+ int i, ret;
size_t readcnt;
ulong kvaddr;
Elf32_Phdr *lp32;
@@ -4436,11 +4436,20 @@ read_proc_kcore(int fd, void *bufptr, int cnt, ulong addr, physaddr_t paddr)
if (offset == UNINITIALIZED)
return SEEK_ERROR;
- if (lseek(fd, offset, SEEK_SET) != offset)
- perror("lseek");
-
- if (read(fd, bufptr, readcnt) != readcnt)
+ if (offset < 0) {
+ if (CRASHDEBUG(8)) {
+ fprintf(fp, "read_proc_kcore: "
+ "invalid offset: %lx\n", offset);
+ }
+ return SEEK_ERROR;
+ }
+ if ((ret = pread(fd, bufptr, readcnt, offset)) != readcnt) {
+ if (ret == -1 && CRASHDEBUG(8)) {
+ fprintf(fp, "read_proc_kcore: "
+ "pread error: %s\n", strerror(errno));
+ }
return READ_ERROR;
+ }
return cnt;
}
Thank you for the update, Tao.
The v2 is expected. So: Ack
Thanks.
Lianbo
--
2.33.1
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