gkfs_functions.cpp

/*
  Copyright 2018-2020, Barcelona Supercomputing Center (BSC), Spain
  Copyright 2015-2020, Johannes Gutenberg Universitaet Mainz, Germany

  This software was partially supported by the
  EC H2020 funded project NEXTGenIO (Project ID: 671951, www.nextgenio.eu).

  This software was partially supported by the
  ADA-FS project under the SPPEXA project funded by the DFG.

  SPDX-License-Identifier: MIT
*/


#include <config.hpp>
#include <client/preload.hpp>
#include <client/preload_util.hpp>
#include <client/logging.hpp>
#include <client/gkfs_functions.hpp>
#include <client/rpc/forward_metadata.hpp>
#include <client/rpc/forward_data.hpp>
#include <client/open_dir.hpp>

#include <global/path_util.hpp>

extern "C" {
#include <dirent.h> // used for file types in the getdents{,64}() functions
#include <linux/kernel.h> // used for definition of alignment macros
#include <sys/statfs.h>
#include <sys/statvfs.h>
}

using namespace std;

/*
 * Macro used within getdents{,64} functions.
 * __ALIGN_KERNEL defined in linux/kernel.h
 */
#define ALIGN(x, a)                     __ALIGN_KERNEL((x), (a))

/*
 * linux_dirent is used in getdents() but is privately defined in the linux kernel: fs/readdir.c.
 */
struct linux_dirent {
    unsigned long d_ino;
    unsigned long d_off;
    unsigned short d_reclen;
    char d_name[1];
};
/*
 * linux_dirent64 is used in getdents64() and defined in the linux kernel: include/linux/dirent.h.
 * However, it is not part of the kernel-headers and cannot be imported.
 */
struct linux_dirent64 {
    uint64_t d_ino;
    int64_t d_off;
    unsigned short d_reclen;
    unsigned char d_type;
    char d_name[1]; // originally `char d_name[0]` in kernel, but ISO C++ forbids zero-size array 'd_name'
};

namespace {

/**
 * Checks if metadata for parent directory exists (can be disabled with CREATE_CHECK_PARENTS).
 * errno may be set
 * @param path
 * @return 0 on success, -1 on failure
 */
int check_parent_dir(const std::string& path) {
#if CREATE_CHECK_PARENTS
    auto p_comp = gkfs::path::dirname(path);
    auto md = gkfs::util::get_metadata(p_comp);
    if (!md) {
        if (errno == ENOENT) {
            LOG(DEBUG, "Parent component does not exist: '{}'", p_comp);
        } else {
            LOG(ERROR, "Failed to get metadata for parent component '{}': {}", path, strerror(errno));
        }
        return -1;
    }
    if (!S_ISDIR(md->mode())) {
        LOG(DEBUG, "Parent component is not a directory: '{}'", p_comp);
        errno = ENOTDIR;
        return -1;
    }
#endif // CREATE_CHECK_PARENTS
    return 0;
}
} // namespace

namespace gkfs {
namespace syscall {

/**
 * gkfs wrapper for open() system calls
 * errno may be set
 * @param path
 * @param mode
 * @param flags
 * @return 0 on success, -1 on failure
 */
int gkfs_open(const std::string& path, mode_t mode, int flags) {

    if (flags & O_PATH) {
        LOG(ERROR, "`O_PATH` flag is not supported");
        errno = ENOTSUP;
        return -1;
    }

    if (flags & O_APPEND) {
        LOG(ERROR, "`O_APPEND` flag is not supported");
        errno = ENOTSUP;
        return -1;
    }

    bool exists = true;
    auto md = gkfs::util::get_metadata(path);
    if (!md) {
        if (errno == ENOENT) {
            exists = false;
        } else {
            LOG(ERROR, "Error while retriving stat to file");
            return -1;
        }
    }

    if (!exists) {
        if (!(flags & O_CREAT)) {
            // file doesn't exists and O_CREAT was not set
            errno = ENOENT;
            return -1;
        }

        /***   CREATION    ***/
        assert(flags & O_CREAT);

        if (flags & O_DIRECTORY) {
            LOG(ERROR, "O_DIRECTORY use with O_CREAT. NOT SUPPORTED");
            errno = ENOTSUP;
            return -1;
        }

        // no access check required here. If one is using our FS they have the permissions.
        if (gkfs_create(path, mode | S_IFREG)) {
            LOG(ERROR, "Error creating non-existent file: '{}'", strerror(errno));
            return -1;
        }
    } else {
        /* File already exists */

        if (flags & O_EXCL) {
            // File exists and O_EXCL was set
            errno = EEXIST;
            return -1;
        }

#ifdef HAS_SYMLINKS
        if (md->is_link()) {
            if (flags & O_NOFOLLOW) {
                LOG(WARNING, "Symlink found and O_NOFOLLOW flag was specified");
                errno = ELOOP;
                return -1;
            }
            return gkfs_open(md->target_path(), mode, flags);
        }
#endif

        if (S_ISDIR(md->mode())) {
            return gkfs_opendir(path);
        }


        /*** Regular file exists ***/
        assert(S_ISREG(md->mode()));

        if ((flags & O_TRUNC) && ((flags & O_RDWR) || (flags & O_WRONLY))) {
            if (gkfs_truncate(path, md->size(), 0)) {
                LOG(ERROR, "Error truncating file");
                return -1;
            }
        }
    }

    return CTX->file_map()->add(std::make_shared<gkfs::filemap::OpenFile>(path, flags));
}

/**
 * Wrapper function for file/directory creation
 * errno may be set
 * @param path
 * @param mode
 * @return 0 on success, -1 on failure
 */
int gkfs_create(const std::string& path, mode_t mode) {

    //file type must be set
    switch (mode & S_IFMT) {
        case 0:
            mode |= S_IFREG;