llapi_file_get_stripe(3)

NAME

llapi_file_get_stripe - get striping information for a file or a directory on a Lustre filesystem

SYNOPSIS

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <lustre/lustreapi.h>

int llapi_file_get_stripe(const char *path, void *lum);

DESCRIPTION

llapi_file_get_stripe() returns striping information for a file or a directory path in lum (which should point to a large enough memory region) in one of the following formats:

struct lov_user_md_v1 {


        __u32 lmm_magic;


        __u32 lmm_pattern;


        __u64 lmm_object_id;


        __u64 lmm_object_seq;


        __u32 lmm_stripe_size;


        __u16 lmm_stripe_count;


        __u16 lmm_stripe_offset;


        struct lov_user_ost_data_v1 lmm_objects[];
} __attribute__((packed));
struct lov_user_md_v3 {


        __u32 lmm_magic;


        __u32 lmm_pattern;


        __u64 lmm_object_id;


        __u64 lmm_object_seq;


        __u32 lmm_stripe_size;


        __u16 lmm_stripe_count;


        __u16 lmm_stripe_offset;


        char  lmm_pool_name[LOV_MAXPOOLNAME + 1];


        struct lov_user_ost_data_v1 lmm_objects[];
} __attribute__((packed));

lmm_magic

specifies the format of the returned striping information. LOV_MAGIC_V1 is used for lov_user_md_v1. LOV_MAGIC_V3 is used for lov_user_md_v3.

lmm_pattern

holds the striping pattern. Only LOV_PATTERN_RAID0 is possible in this Lustre version.

lmm_object_id

holds the MDS object id.

lmm_object_gr

holds the MDS object group.

lmm_stripe_size

holds the stripe size in bytes.

lmm_stripe_count

holds the number of OSTs the file is striped across.

lmm_stripe_offset

holds the OST index from which the file starts.

lmm_pool_name

holds the OST pool name to which the file belongs.

lmm_objects

is an array of lmm_stripe_count members containing per OST file information in the following format:

struct lov_user_ost_data_v1 {


        __u64 l_object_id;


        __u64 l_object_seq;


        __u32 l_ost_gen;


        __u32 l_ost_idx;
} __attribute__((packed));

l_object_id

holds the OST object id.

l_object_seq

holds the OST object group.

l_ost_gen

holds the generation of the OST index.

l_ost_idx

holds the OST index in LOV.

RETURN VALUES

llapi_file_get_stripe() returns:

0

on success

!= 0

on failure, errno is set appropriately.

ERRORS

ENOMEM

failed to allocate memory.

ENAMETOOLONG

path was too long.

ENOENT

path does not point to a file or a directory.

ENOTTY

path does not point to a Lustre filesystem.

EFAULT

memory region pointed by lum is not properly mapped.

EXAMPLES

#include <sys/vfs.h>
#include <lustre/lustreapi.h>
static inline int maxint(int a, int b)
{


        return a > b ? a : b;
}
static void *alloc_lum()
{


        int v1, v3, join;


        v1 = sizeof(struct lov_user_md_v1) +


             LOV_MAX_STRIPE_COUNT * sizeof(struct lov_user_ost_data_v1);


        v3 = sizeof(struct lov_user_md_v3) +


             LOV_MAX_STRIPE_COUNT * sizeof(struct lov_user_ost_data_v1);


        return malloc(maxint(v1, v3));
}
int main(int argc, char** argv)
{


        struct lov_user_md *lum_file = NULL;


        int rc;


        int lum_size;


        if (argc != 2) {


                fprintf(stderr, "Usage: %s <filename>\n", argv[0]);


                return 1;


        }


        lum_file = alloc_lum();


        if (lum_file == NULL) {


                rc = ENOMEM;


                goto cleanup;


        }


        rc = llapi_file_get_stripe(argv[1], lum_file);


        if (rc) {


                rc = errno;


                goto cleanup;


        }


        /* stripe_size stripe_count */


        printf("%d %d\n",


               lum_file->lmm_stripe_size,


               lum_file->lmm_stripe_count);
cleanup:


        if (lum_file != NULL)


                free(lum_file);


        return rc;
}

AVAILABILITY

llapi_file_get_stripe() is part of the lustre(7) user application interface library since release 2.4.0

SEE ALSO

lustre(7), lustreapi(7)