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    Subject[PATCH 0/6][TAKE7] fallocate system call
    This is the latest fallocate patchset and is based on 2.6.22.

    * Following are the changes from TAKE6:
    1) We now just have two modes (and no deallocation modes).
    2) Updated the man page
    3) Added a new patch submitted by David P. Quigley (Patch 3/6).
    4) Used EXT_INIT_MAX_LEN instead of 0x8000 in Patch 6/6.
    5) Included below in the end is a small testcase to test fallocate.

    * Following are the changes from TAKE5 to TAKE6:
    1) Rebased to 2.6.22
    2) Added compat wrapper for x86_64
    3) Dropped s390 and ia64 patches, since the platform maintaners can
    add the support for fallocate once it is in mainline.
    4) Added a change suggested by Andreas for better extent-to-group
    alignment in ext4 (Patch 6/6). Please refer following post:
    5) Renamed mode flags and values from "FA_" to "FALLOC_"
    6) Added manpage (updated version of the one initially submitted by
    David Chinner).

    1> Implementation on other architectures (other than i386, x86_64,
    and ppc64). s390(x) and ia64 patches are ready and will be pushed
    by platform maintaners when the fallocate is in mainline.
    2> A generic file system operation to handle fallocate
    (generic_fallocate), for filesystems that do _not_ have the fallocate
    inode operation implemented.
    3> Changes to glibc,
    a) to support fallocate() system call
    b) to make posix_fallocate() and posix_fallocate64() call fallocate()
    4> Patch to e2fsprogs to recognize and display uninitialized extents.

    Following patches follow:
    Patch 1/6 : manpage for fallocate
    Patch 2/6 : fallocate() implementation in i386, x86_64 and powerpc
    Patch 3/6 : revalidate write permissions for fallocate
    Patch 4/6 : ext4: fallocate support in ext4
    Patch 5/6 : ext4: write support for preallocated blocks
    Patch 6/6 : ext4: change for better extent-to-group alignment

    Note: Attached below is a small testcase to test fallocate. The __NR_fallocate
    will need to be changed depending on the system call number in the kernel (it
    may get changed due to merge) and also depending on the architecture.

    Amit Arora

    #include <stdio.h>
    #include <stdlib.h>
    #include <fcntl.h>
    #include <errno.h>

    #include <linux/unistd.h>
    #include <sys/vfs.h>
    #include <sys/stat.h>

    #define VERBOSE 0

    #define __NR_fallocate 324

    #define FALLOC_FL_KEEP_SIZE 0x01
    #define FALLOC_ALLOCATE 0x0

    int do_fallocate(int fd, int mode, loff_t offset, loff_t len)
    int ret;

    if (VERBOSE)
    printf("Trying to preallocate blocks (offset=%llu, len=%llu)\n",
    offset, len);
    ret = syscall(__NR_fallocate, fd, mode, offset, len);

    if (ret <0) {
    printf("SYSCALL: received error %d, ret=%d\n", errno, ret);

    if (VERBOSE)
    printf("fallocate system call succedded ! ret=%d\n", ret);

    return ret;

    int test_fallocate(int fd, int mode, loff_t offset, loff_t len)
    int ret, blocks;
    struct stat statbuf1, statbuf2;

    fstat(fd, &statbuf1);

    ret = do_fallocate(fd, mode, offset, len);

    fstat(fd, &statbuf2);

    /* check file size after preallocation */
    if (mode == FALLOC_ALLOCATE) {
    if (!ret && statbuf1.st_size < (offset + len) &&
    statbuf2.st_size != (offset + len)) {
    printf("Error: fallocate succeeded, but the file size did not "
    "change, where it should have!\n");
    ret = 1;
    } else if (statbuf1.st_size != statbuf2.st_size) {
    printf("Error : File size changed, when it should not have!\n");
    ret = 1;

    blocks = ((statbuf2.st_blocks - statbuf1.st_blocks) * 512)/ statbuf2.st_blksize;

    /* Print report */
    printf("# FALLOCATE TEST REPORT #\n");
    printf("\tNew blocks preallocated = %d.\n", blocks);
    printf("\tNumber of bytes preallocated = %d\n", blocks * statbuf2.st_blksize);
    printf("\tOld file size = %d, New file size %d.\n",
    statbuf1.st_size, statbuf2.st_size);
    printf("\tOld num blocks = %d, New num blocks %d.\n",
    (statbuf1.st_blocks * 512)/1024, (statbuf2.st_blocks * 512)/1024);

    return ret;

    int do_write(int fd, loff_t offset, loff_t len)
    int ret;
    char *buf;

    buf = (char *)malloc(len);
    if (!buf) {
    printf("error: malloc failed.\n");

    if (VERBOSE)
    printf("Trying to write to file (offset=%llu, len=%llu)\n",
    offset, len);

    ret = lseek(fd, offset, SEEK_SET);
    if (ret != offset) {
    printf("lseek() failed error=%d, ret=%d\n", errno, ret);

    ret = write(fd, buf, len);
    if (ret != len) {
    printf("write() failed error=%d, ret=%d\n", errno, ret);

    if (VERBOSE)
    printf("Write succedded ! Written %llu bytes ret=%d\n", len, ret);

    return ret;

    int test_write(int fd, loff_t offset, loff_t len)
    int ret;

    ret = do_write(fd, offset, len);
    printf("# WRITE TEST REPORT #\n");
    if (ret > 0) printf("\t written %d bytes.\n", ret);
    else printf("\t write operation failed!\n");

    if (ret > 0) return 0;
    else return 1;

    void usage(char **argv)
    printf("\n%s <option> <filename-with-path> <offset> <length>\n", argv[0]);
    printf("option can be one of the following :\n");
    printf("\t-f\t: preallocate. This maps to FALLOC_ALLOCATE mode.\n");
    printf("\t-F\t: preallocate, but do not change the file size.\n");
    printf("\t\t This maps to FALLOC_RESV_SPACE mode.\n");
    printf("\t-w\t: write some data to the range.\n");
    printf("\t-W\t: preallocate and write some data to the range.\n");

    * Arguments:
    * argv[1] = option (-f/-F/-w/-W/-m)
    * argv[2] = fname : the file name with path
    * argv[3] = offset : in bytes
    * argv[4] = len : in bytes
    int main(int argc, char **argv)
    int ret = 1, fd, mode;
    char *fname;
    loff_t offset, len;

    if (argc!=5 || argv[1][0] != '-') {

    fname = argv[2];
    offset = (unsigned long long)atol(argv[3]);;
    len = (unsigned long long)atol(argv[4]);

    if (offset < 0 || len <= 0) {
    printf("%s: Invalid arguments.\n", argv[0]);

    fd = open(fname, O_CREAT|O_RDWR, 0666);
    if (fd < 0) {
    printf("Error opening file %s, error = %d.\n", fname, errno);

    /* -f */
    if (!strcmp(argv[1], "-f")) {
    ret = test_fallocate(fd, mode, offset, len);
    if (ret) printf("test_fallocate: ERROR ! ret=%d\n", ret);
    /* -F */
    } else if (!strcmp(argv[1], "-F")) {
    ret = test_fallocate(fd, mode, offset, len);
    if (ret) printf("test_fallocate: ERROR ! ret=%d\n", ret);
    /* -w */
    } else if (!strcmp(argv[1], "-w")) {
    ret = test_write(fd, offset, len);
    /* -W */
    } else if (!strcmp(argv[1], "-W")) {
    ret = test_fallocate(fd, mode, offset, len);
    if (ret) {
    printf("test_fallocate: ERROR ! ret=%d\n", ret);
    goto out;
    ret = test_write(fd, offset, len);
    if (ret) printf("test_write: ERROR ! ret=%d\n", ret);
    } else {
    printf("%s: Invalid arguments.\n", argv[0]);


    if (!ret) printf("\n\n### TESTS PASSED ###\n");
    else printf("\n\n#!# TESTS FAILED #!#\n");

    return ret;
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      Last update: 2007-07-13 14:42    [W:0.033 / U:44.796 seconds]
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