// SPDX-License-Identifier: GPL-2.0
/*
 * High-level sync()-related operations
 */

#include <linux/blkdev.h>
#include <linux/kernel.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/export.h>
#include <linux/namei.h>
#include <linux/sched.h>
#include <linux/writeback.h>
#include <linux/syscalls.h>
#include <linux/linkage.h>
#include <linux/pagemap.h>
#include <linux/quotaops.h>
#include <linux/backing-dev.h>
#include "internal.h"

#define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
                        SYNC_FILE_RANGE_WAIT_AFTER)

/*
 * Write out and wait upon all dirty data associated with this
 * superblock.  Filesystem data as well as the underlying block
 * device.  Takes the superblock lock.
 */
int sync_filesystem(struct super_block *sb)
{
        int ret = 0;

        /*
         * We need to be protected against the filesystem going from
         * r/o to r/w or vice versa.
         */
        WARN_ON(!rwsem_is_locked(&sb->s_umount));

        /*
         * No point in syncing out anything if the filesystem is read-only.
         */
        if (sb_rdonly(sb))
                return 0;

        /*
         * Do the filesystem syncing work.  For simple filesystems
         * writeback_inodes_sb(sb) just dirties buffers with inodes so we have
         * to submit I/O for these buffers via sync_blockdev().  This also
         * speeds up the wait == 1 case since in that case write_inode()
         * methods call sync_dirty_buffer() and thus effectively write one block
         * at a time.
         */
        writeback_inodes_sb(sb, WB_REASON_SYNC);
        if (sb->s_op->sync_fs) {
                ret = sb->s_op->sync_fs(sb, 0);
                if (ret)
                        return ret;
        }
        ret = sync_blockdev_nowait(sb->s_bdev);
        if (ret)
                return ret;

        sync_inodes_sb(sb);
        if (sb->s_op->sync_fs) {
                ret = sb->s_op->sync_fs(sb, 1);
                if (ret)
                        return ret;
        }
        return sync_blockdev(sb->s_bdev);
}
EXPORT_SYMBOL(sync_filesystem);

static void sync_inodes_one_sb(struct super_block *sb, void *arg)
{
        if (!sb_rdonly(sb))
                sync_inodes_sb(sb);
}

static void sync_fs_one_sb(struct super_block *sb, void *arg)
{
        if (!sb_rdonly(sb) && !(sb->s_iflags & SB_I_SKIP_SYNC) &&
            sb->s_op->sync_fs)
                sb->s_op->sync_fs(sb, *(int *)arg);
}

/*
 * Sync everything. We start by waking flusher threads so that most of
 * writeback runs on all devices in parallel. Then we sync all inodes reliably
 * which effectively also waits for all flusher threads to finish doing
 * writeback. At this point all data is on disk so metadata should be stable
 * and we tell filesystems to sync their metadata via ->sync_fs() calls.
 * Finally, we writeout all block devices because some filesystems (e.g. ext2)
 * just write metadata (such as inodes or bitmaps) to block device page cache
 * and do not sync it on their own in ->sync_fs().
 */
void ksys_sync(void)
{
        int nowait = 0, wait = 1;

        wakeup_flusher_threads(WB_REASON_SYNC);
        iterate_supers(sync_inodes_one_sb, NULL);
        iterate_supers(sync_fs_one_sb, &nowait);
        iterate_supers(sync_fs_one_sb, &wait);
        sync_bdevs(false);
        sync_bdevs(true);
}

SYSCALL_DEFINE0(sync)
{
        ksys_sync();
        return 0;
}

static void do_sync_work(struct work_struct *work)
{
        int nowait = 0;
        int wait = 1;

        /*
         * Sync twice to reduce the possibility we skipped some inodes / pages
         * because they were temporarily locked
         */
        iterate_supers(sync_inodes_one_sb, NULL);
        iterate_supers(sync_fs_one_sb, &nowait);
        sync_bdevs(false);
        iterate_supers(sync_inodes_one_sb, NULL);
        iterate_supers(sync_fs_one_sb, &wait);
        sync_bdevs(false);
        printk("Emergency Sync complete\n");
        kfree(work);
}

void emergency_sync(void)
{
        struct work_struct *work;

        work = kmalloc_obj(*work, GFP_ATOMIC);
        if (work) {
                INIT_WORK(work, do_sync_work);
                schedule_work(work);
        }
}

/*
 * sync a single super
 */
SYSCALL_DEFINE1(syncfs, int, fd)
{
        CLASS(fd, f)(fd);
        struct super_block *sb;
        int ret, ret2;

        if (fd_empty(f))
                return -EBADF;
        sb = fd_file(f)->f_path.dentry->d_sb;

        down_read(&sb->s_umount);
        ret = sync_filesystem(sb);
        up_read(&sb->s_umount);

        ret2 = errseq_check_and_advance(&sb->s_wb_err, &fd_file(f)->f_sb_err);

        return ret ? ret : ret2;
}

/**
 * vfs_fsync_range - helper to sync a range of data & metadata to disk
 * @file:               file to sync
 * @start:              offset in bytes of the beginning of data range to sync
 * @end:                offset in bytes of the end of data range (inclusive)
 * @datasync:           perform only datasync
 *
 * Write back data in range @start..@end and metadata for @file to disk.  If
 * @datasync is set only metadata needed to access modified file data is
 * written.
 */
int vfs_fsync_range(struct file *file, loff_t start, loff_t end, int datasync)
{
        struct inode *inode = file->f_mapping->host;

        if (!file->f_op->fsync)
                return -EINVAL;
        if (!datasync)
                sync_lazytime(inode);
        return file->f_op->fsync(file, start, end, datasync);
}
EXPORT_SYMBOL(vfs_fsync_range);

/**
 * vfs_fsync - perform a fsync or fdatasync on a file
 * @file:               file to sync
 * @datasync:           only perform a fdatasync operation
 *
 * Write back data and metadata for @file to disk.  If @datasync is
 * set only metadata needed to access modified file data is written.
 */
int vfs_fsync(struct file *file, int datasync)
{
        return vfs_fsync_range(file, 0, LLONG_MAX, datasync);
}
EXPORT_SYMBOL(vfs_fsync);

static int do_fsync(unsigned int fd, int datasync)
{
        CLASS(fd, f)(fd);

        if (fd_empty(f))
                return -EBADF;

        return vfs_fsync(fd_file(f), datasync);
}

SYSCALL_DEFINE1(fsync, unsigned int, fd)
{
        return do_fsync(fd, 0);
}

SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
{
        return do_fsync(fd, 1);
}

int sync_file_range(struct file *file, loff_t offset, loff_t nbytes,
                    unsigned int flags)
{
        int ret;
        struct address_space *mapping;
        loff_t endbyte;                 /* inclusive */
        umode_t i_mode;

        ret = -EINVAL;
        if (flags & ~VALID_FLAGS)
                goto out;

        endbyte = offset + nbytes;

        if ((s64)offset < 0)
                goto out;
        if ((s64)endbyte < 0)
                goto out;
        if (endbyte < offset)
                goto out;

        if (sizeof(pgoff_t) == 4) {
                if (offset >= (0x100000000ULL << PAGE_SHIFT)) {
                        /*
                         * The range starts outside a 32 bit machine's
                         * pagecache addressing capabilities.  Let it "succeed"
                         */
                        ret = 0;
                        goto out;
                }
                if (endbyte >= (0x100000000ULL << PAGE_SHIFT)) {
                        /*
                         * Out to EOF
                         */
                        nbytes = 0;
                }
        }

        if (nbytes == 0)
                endbyte = LLONG_MAX;
        else
                endbyte--;              /* inclusive */

        i_mode = file_inode(file)->i_mode;
        ret = -ESPIPE;
        if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
                        !S_ISLNK(i_mode))
                goto out;

        mapping = file->f_mapping;
        ret = 0;
        if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
                ret = file_fdatawait_range(file, offset, endbyte);
                if (ret < 0)
                        goto out;
        }

        if (flags & SYNC_FILE_RANGE_WRITE) {
                if ((flags & SYNC_FILE_RANGE_WRITE_AND_WAIT) ==
                             SYNC_FILE_RANGE_WRITE_AND_WAIT)
                        ret = filemap_fdatawrite_range(mapping, offset,
                                        endbyte);
                else
                        ret = filemap_flush_range(mapping, offset, endbyte);
                if (ret < 0)
                        goto out;
        }

        if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
                ret = file_fdatawait_range(file, offset, endbyte);

out:
        return ret;
}

/*
 * ksys_sync_file_range() permits finely controlled syncing over a segment of
 * a file in the range offset .. (offset+nbytes-1) inclusive.  If nbytes is
 * zero then ksys_sync_file_range() will operate from offset out to EOF.
 *
 * The flag bits are:
 *
 * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
 * before performing the write.
 *
 * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
 * range which are not presently under writeback. Note that this may block for
 * significant periods due to exhaustion of disk request structures.
 *
 * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
 * after performing the write.
 *
 * Useful combinations of the flag bits are:
 *
 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
 * in the range which were dirty on entry to ksys_sync_file_range() are placed
 * under writeout.  This is a start-write-for-data-integrity operation.
 *
 * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
 * are not presently under writeout.  This is an asynchronous flush-to-disk
 * operation.  Not suitable for data integrity operations.
 *
 * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
 * completion of writeout of all pages in the range.  This will be used after an
 * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
 * for that operation to complete and to return the result.
 *
 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER
 * (a.k.a. SYNC_FILE_RANGE_WRITE_AND_WAIT):
 * a traditional sync() operation.  This is a write-for-data-integrity operation
 * which will ensure that all pages in the range which were dirty on entry to
 * ksys_sync_file_range() are written to disk.  It should be noted that disk
 * caches are not flushed by this call, so there are no guarantees here that the
 * data will be available on disk after a crash.
 *
 *
 * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
 * I/O errors or ENOSPC conditions and will return those to the caller, after
 * clearing the EIO and ENOSPC flags in the address_space.
 *
 * It should be noted that none of these operations write out the file's
 * metadata.  So unless the application is strictly performing overwrites of
 * already-instantiated disk blocks, there are no guarantees here that the data
 * will be available after a crash.
 */
int ksys_sync_file_range(int fd, loff_t offset, loff_t nbytes,
                         unsigned int flags)
{
        CLASS(fd, f)(fd);

        if (fd_empty(f))
                return -EBADF;

        return sync_file_range(fd_file(f), offset, nbytes, flags);
}

SYSCALL_DEFINE4(sync_file_range, int, fd, loff_t, offset, loff_t, nbytes,
                                unsigned int, flags)
{
        return ksys_sync_file_range(fd, offset, nbytes, flags);
}

#if defined(CONFIG_COMPAT) && defined(__ARCH_WANT_COMPAT_SYNC_FILE_RANGE)
COMPAT_SYSCALL_DEFINE6(sync_file_range, int, fd, compat_arg_u64_dual(offset),
                       compat_arg_u64_dual(nbytes), unsigned int, flags)
{
        return ksys_sync_file_range(fd, compat_arg_u64_glue(offset),
                                    compat_arg_u64_glue(nbytes), flags);
}
#endif

/* It would be nice if people remember that not all the world's an i386
   when they introduce new system calls */
SYSCALL_DEFINE4(sync_file_range2, int, fd, unsigned int, flags,
                                 loff_t, offset, loff_t, nbytes)
{
        return ksys_sync_file_range(fd, offset, nbytes, flags);
}