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0676806707
I met a odd prblem:read /proc/partitions may return zero. I wrote a file test.c: int main() { char buff[4096]; int ret; int fd; printf("pid=%d\n",getpid()); while (1) { fd = open("/proc/partitions", O_RDONLY); if (fd < 0) { printf("open error %s\n", strerror(errno)); return 0; } ret = read(fd, buff, 4096); if (ret <= 0) printf("ret=%d, %s, %ld\n", ret, strerror(errno), lseek(fd,0,SEEK_CUR)); close(fd); } exit(0); } You can reproduce by: 1:while true;do cat /proc/partitions > /dev/null ;done 2:./test I reviewed the code and found: >> static void *show_partition_start(struct seq_file *seqf, loff_t *pos) >> { >> static void *p; >> >> p = disk_seqf_start(seqf, pos); >> if (!IS_ERR_OR_NULL(p) && !*pos) >> seq_puts(seqf, "major minor #blocks name\n\n"); >> return p; >> } test cat /proc/partitions p = disk_seqf_start()(Not NULL) p = disk_seqf_start()(NULL because pos) if (!IS_ERR_OR_NULL(p) && !*pos) Signed-off-by: Jianpeng Ma <majianpeng@gmail.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> |
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.. | ||
partitions | ||
blk-cgroup.c | ||
blk-cgroup.h | ||
blk-core.c | ||
blk-exec.c | ||
blk-flush.c | ||
blk-integrity.c | ||
blk-ioc.c | ||
blk-iopoll.c | ||
blk-lib.c | ||
blk-map.c | ||
blk-merge.c | ||
blk-settings.c | ||
blk-softirq.c | ||
blk-sysfs.c | ||
blk-tag.c | ||
blk-throttle.c | ||
blk-timeout.c | ||
blk.h | ||
bsg-lib.c | ||
bsg.c | ||
cfq-iosched.c | ||
compat_ioctl.c | ||
deadline-iosched.c | ||
elevator.c | ||
genhd.c | ||
ioctl.c | ||
Kconfig | ||
Kconfig.iosched | ||
Makefile | ||
noop-iosched.c | ||
partition-generic.c | ||
scsi_ioctl.c |