plfs_read not working with small files about plfs-core HOT 5 CLOSED

From the following lines:

char *outstr = NULL;
ssize_t bytes_read = 0;

plfs_error = plfs_write(fd, outstr, size, offset, pid, &bytes_read); // This should be plfs_read()

I think that you forget to allocate storage space for the 'outstr', so it's a NULL pointer and which is not correct for plfs_read(). And you use plfs_write instead of plfs_read mistakenly. You can try code like this to allocate the output buffer at stack:

char outstr[16];
ssize_t bytes_read = 0;

printf("Executing 'plfs_read(0x%0x, \"%s\", %d, %d, %d, %d)'\n", fd, outstr, size, offset, pid, bytes_read);
plfs_error = plfs_read(fd, outstr, size, offset, pid, &bytes_read);

from plfs-core.

Thanks, Zhang. That was pretty dense of me. Unfortunately, it still
doesn't seem to be quite correct for some reason. After making the
change you suggested, even though plfs_error is 0 and bytes read is 5,
outstr still has whatever garbage was in it after the declaration. If I
initialize it, the initialized value is returned. What's very
interesting, is that in a different context (from ldplfs) if I preload
the return buffer with "dummy" and pass it to plfs_read to read 3
characters, it returns "xxxmy" which indicates to me that plfs is
returning only the z's that it uses to initialize it's buffer. Anyway,
here is the altered code and output:

#include <stdio.h>
#include <plfs.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>

#define SUCCESS 0

int main(int argc, char **argv) {
const char *cpath = "/tmp/local_plfs/test.plfs.fil";
//mode_t fmode = "w+";
mode_t fmode = 0666;
Plfs_fd *fd = NULL;

//printf("fd = 0x%0x\n", fd);
//printf("cpath = %s\n", cpath);
//printf("O_RDWR = %d\n", O_RDWR);
//printf("getpid() = %d\n", getpid());
//printf("fmode = %d\n", fmode);

printf("Executing 'plfs_open(0x%0x, \"%s\", %d, %d, %d, NULL)'\n",

fd, cpath, O_RDWR, getpid(), fmode);
plfs_error_t plfs_error = plfs_open(&fd, cpath, O_RDWR, getpid(),
fmode, NULL);
printf("plfs_error = %d\n", plfs_error);
printf("fd = 0x%0x\n\n", fd);

const char *str = "Hello";
const int size = strlen(str);
const int offset = 0;
const pid_t pid = getpid();
ssize_t written = 0;

printf("Executing 'plfs_write(0x%0x, %0x0x, %d, %d, %d, %d)'\n", fd,

str, size, offset, pid, written);
plfs_error = plfs_write(fd, str, size, offset, pid, &written);
printf("plfs_error = %d\n", plfs_error);
printf("written = %d\n\n", written);

char outstr[16];
//outstr[0] = '\0';
//strcpy(outstr, "abcdefghijklm");
ssize_t bytes_read = 0;

printf("outstr = %s\n", outstr);
printf("Executing 'plfs_read(0x%0x, 0x%0x, %d, %d, %d, %d)'\n", fd,

outstr, size, offset, pid, bytes_read);
plfs_error = plfs_write(fd, outstr, size, offset, pid, &bytes_read);
printf("plfs_error = %d\n", plfs_error);
printf("bytes_read = %d\n", bytes_read);
printf("outstr = %s\n\n ", outstr);

Plfs_close_opt opts; 
int x;
printf("Executing 'plfs_close(0x%0x, %d, %d, %d, %d, NULL)'\n", fd,

pid, getuid(), O_RDWR, NULL, x);
plfs_error = plfs_close(fd, pid, getuid(), O_RDWR, NULL, &x);
printf("plfs_error = %d\n", plfs_error);

return SUCCESS;

}

Executing 'plfs_open(0x0, "/tmp/local_plfs/test.plfs.fil", 2, 54673,
438, NULL)'
plfs_error = 0
fd = 0x24c88e0

Executing 'plfs_write(0x24c88e0, 400c5c0x, 5, 0, 54673, 0)'
plfs_error = 0
written = 5

outstr = N�8YD+
Executing 'plfs_read(0x24c88e0, 0x4a2de670, 5, 0, 54673, 0)'
plfs_error = 0
bytes_read = 5
outstr = N�8YD+

Executing 'plfs_close(0x24c88e0, 54673, 55096, 2, 0, NULL)'
plfs_error = 0

On Mon, 2015-03-16 at 18:41 -0700, Zhang Jingwang wrote:

From the following lines:

char *outstr = NULL;
ssize_t bytes_read = 0;

plfs_error = plfs_write(fd, outstr, size, offset, pid, &bytes_read);

I think that you forget to allocate storage space for the 'outstr', so
it's a NULL pointer and which is not correct for plfs_read(). You can
try code like this to allocate the output buffer at stack:

char outstr[16];
ssize_t bytes_read = 0;

printf("Executing 'plfs_read(0x%0x, "%s", %d, %d, %d, %d)'\n", fd, outstr, size, offset, pid, bytes_read);
plfs_error = plfs_write(fd, outstr, size, offset, pid, &bytes_read);

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from plfs-core.

I will consult with someone today that may be able to talk to the developer of small file mode.

Alfred

From: krigbaum <[email protected]mailto:[email protected]>
Reply-To: plfs/plfs-core <[email protected]mailto:[email protected]>
Date: Tue, 17 Mar 2015 05:40:56 -0700
To: plfs/plfs-core <[email protected]mailto:[email protected]>
Subject: Re: [plfs-core] plfs_read not working with small files (#360)

Thanks, Zhang. That was pretty dense of me. Unfortunately, it still
doesn't seem to be quite correct for some reason. After making the
change you suggested, even though plfs_error is 0 and bytes read is 5,
outstr still has whatever garbage was in it after the declaration. If I
initialize it, the initialized value is returned. What's very
interesting, is that in a different context (from ldplfs) if I preload
the return buffer with "dummy" and pass it to plfs_read to read 3
characters, it returns "xxxmy" which indicates to me that plfs is
returning only the z's that it uses to initialize it's buffer. Anyway,
here is the altered code and output:

#include <stdio.h>
#include <plfs.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/types.h>

#define SUCCESS 0

int main(int argc, char **argv) {
const char *cpath = "/tmp/local_plfs/test.plfs.fil";
//mode_t fmode = "w+";
mode_t fmode = 0666;
Plfs_fd *fd = NULL;

//printf("fd = 0x%0x\n", fd);
//printf("cpath = %s\n", cpath);
//printf("O_RDWR = %d\n", O_RDWR);
//printf("getpid() = %d\n", getpid());
//printf("fmode = %d\n", fmode);

printf("Executing 'plfs_open(0x%0x, "%s", %d, %d, %d, NULL)'\n",
fd, cpath, O_RDWR, getpid(), fmode);
plfs_error_t plfs_error = plfs_open(&fd, cpath, O_RDWR, getpid(),
fmode, NULL);
printf("plfs_error = %d\n", plfs_error);
printf("fd = 0x%0x\n\n", fd);

const char *str = "Hello";
const int size = strlen(str);
const int offset = 0;
const pid_t pid = getpid();
ssize_t written = 0;

printf("Executing 'plfs_write(0x%0x, %0x0x, %d, %d, %d, %d)'\n", fd,
str, size, offset, pid, written);
plfs_error = plfs_write(fd, str, size, offset, pid, &written);
printf("plfs_error = %d\n", plfs_error);
printf("written = %d\n\n", written);

char outstr[16];
//outstr[0] = '\0';
//strcpy(outstr, "abcdefghijklm");
ssize_t bytes_read = 0;

printf("outstr = %s\n", outstr);
printf("Executing 'plfs_read(0x%0x, 0x%0x, %d, %d, %d, %d)'\n", fd,
outstr, size, offset, pid, bytes_read);
plfs_error = plfs_write(fd, outstr, size, offset, pid, &bytes_read);
printf("plfs_error = %d\n", plfs_error);
printf("bytes_read = %d\n", bytes_read);
printf("outstr = %s\n\n ", outstr);

Plfs_close_opt opts;
int x;
printf("Executing 'plfs_close(0x%0x, %d, %d, %d, %d, NULL)'\n", fd,
pid, getuid(), O_RDWR, NULL, x);
plfs_error = plfs_close(fd, pid, getuid(), O_RDWR, NULL, &x);
printf("plfs_error = %d\n", plfs_error);

return SUCCESS;
}

Executing 'plfs_open(0x0, "/tmp/local_plfs/test.plfs.fil", 2, 54673,
438, NULL)'
plfs_error = 0
fd = 0x24c88e0

Executing 'plfs_write(0x24c88e0, 400c5c0x, 5, 0, 54673, 0)'
plfs_error = 0
written = 5

outstr = N�8YD+
Executing 'plfs_read(0x24c88e0, 0x4a2de670, 5, 0, 54673, 0)'
plfs_error = 0
bytes_read = 5
outstr = N�8YD+

Executing 'plfs_close(0x24c88e0, 54673, 55096, 2, 0, NULL)'
plfs_error = 0

On Mon, 2015-03-16 at 18:41 -0700, Zhang Jingwang wrote:

From the following lines:

char *outstr = NULL;
ssize_t bytes_read = 0;

plfs_error = plfs_write(fd, outstr, size, offset, pid, &bytes_read);

I think that you forget to allocate storage space for the 'outstr', so
it's a NULL pointer and which is not correct for plfs_read(). You can
try code like this to allocate the output buffer at stack:

char outstr[16];
ssize_t bytes_read = 0;

printf("Executing 'plfs_read(0x%0x, "%s", %d, %d, %d, %d)'\n", fd, outstr, size, offset, pid, bytes_read);
plfs_error = plfs_write(fd, outstr, size, offset, pid, &bytes_read);

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from plfs-core.

hi-

you are printing "Executing plfs_read"  but you appear to

actually be calling plfs_write()?

chuck

On Tue, Mar 17, 2015 at 05:40:57AM -0700, krigbaum wrote:

printf("outstr = %s\n", outstr);
printf("Executing 'plfs_read(0x%0x, 0x%0x, %d, %d, %d, %d)'\n", fd,

outstr, size, offset, pid, bytes_read);
plfs_error = plfs_write(fd, outstr, size, offset, pid, &bytes_read);
^^^^^^^^^^^
printf("plfs_error = %d\n", plfs_error);
printf("bytes_read = %d\n", bytes_read);
printf("outstr = %s\n\n ", outstr);

from plfs-core.

Thanks. Excuse me while I go find a rock to hide under.

On Tue, 2015-03-17 at 06:37 -0700, chuckcranor wrote:

hi-

you are printing "Executing plfs_read" but you appear to
actually be calling plfs_write()?

chuck

On Tue, Mar 17, 2015 at 05:40:57AM -0700, krigbaum wrote:

printf("outstr = %s\n", outstr);
printf("Executing 'plfs_read(0x%0x, 0x%0x, %d, %d, %d, %d)'\n", fd,
outstr, size, offset, pid, bytes_read);
plfs_error = plfs_write(fd, outstr, size, offset, pid, &bytes_read);
^^^^^^^^^^^
printf("plfs_error = %d\n", plfs_error);
printf("bytes_read = %d\n", bytes_read);
printf("outstr = %s\n\n ", outstr);

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from plfs-core.