sync.c

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/*
 * High-level sync()-related operations
 */

#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)

/*
 * Do the filesystem syncing work. For simple filesystems
 * writeback_inodes_sb(sb) just dirties buffers with inodes so we have to
 * submit IO for these buffers via __sync_blockdev(). This also speeds up the
 * wait == 1 case since in that case write_inode() functions do
 * sync_dirty_buffer() and thus effectively write one block at a time.
 */
static int __sync_filesystem(struct super_block *sb, int wait)
{
    if (wait)
        sync_inodes_sb(sb);
    else
        writeback_inodes_sb(sb, WB_REASON_SYNC);

    if (sb->s_op->sync_fs)
        sb->s_op->sync_fs(sb, wait);
    return __sync_blockdev(sb->s_bdev, wait);
}

/*
 * 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;

    /*
     * 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->s_flags & MS_RDONLY)
        return 0;

    ret = __sync_filesystem(sb, 0);
    if (ret < 0)
        return ret;
    return __sync_filesystem(sb, 1);
}
EXPORT_SYMBOL_GPL(sync_filesystem);

static void sync_inodes_one_sb(struct super_block *sb, void *arg)
{
    if (!(sb->s_flags & MS_RDONLY))
        sync_inodes_sb(sb);
}

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

static void fdatawrite_one_bdev(struct block_device *bdev, void *arg)
{
    filemap_fdatawrite(bdev->bd_inode->i_mapping);
}

static void fdatawait_one_bdev(struct block_device *bdev, void *arg)
{
    filemap_fdatawait(bdev->bd_inode->i_mapping);
}

/*
 * 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().
 */
SYSCALL_DEFINE0(sync)
{
    int nowait = 0, wait = 1;

    wakeup_flusher_threads(0, WB_REASON_SYNC);
    iterate_supers(sync_inodes_one_sb, NULL);
    iterate_supers(sync_fs_one_sb, &nowait);
    iterate_supers(sync_fs_one_sb, &wait);
    iterate_bdevs(fdatawrite_one_bdev, NULL);
    iterate_bdevs(fdatawait_one_bdev, NULL);
    if (unlikely(laptop_mode))
        laptop_sync_completion();
    return 0;
}

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

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

void emergency_sync(void)
{
    struct work_struct *work;

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

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

    if (!f.file)
        return -EBADF;
    sb = f.file->f_dentry->d_sb;

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

    fdput(f);
    return ret;
}

int vfs_fsync_range(struct file *file, loff_t start, loff_t end, int datasync)
{
    if (!file->f_op || !file->f_op->fsync)
        return -EINVAL;
    return file->f_op->fsync(file, start, end, datasync);
}
EXPORT_SYMBOL(vfs_fsync_range);

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)
{
    struct fd f = fdget(fd);
    int ret = -EBADF;

    if (f.file) {
        ret = vfs_fsync(f.file, datasync);
        fdput(f);
    }
    return ret;
}

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

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

int generic_write_sync(struct file *file, loff_t pos, loff_t count)
{
    if (!(file->f_flags & O_DSYNC) && !IS_SYNC(file->f_mapping->host))
        return 0;
    return vfs_fsync_range(file, pos, pos + count - 1,
                   (file->f_flags & __O_SYNC) ? 0 : 1);
}
EXPORT_SYMBOL(generic_write_sync);

/*
 * sys_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 sys_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 sys_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 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
 * sys_sync_file_range() are committed to disk.
 *
 *
 * 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.
 */
SYSCALL_DEFINE(sync_file_range)(int fd, loff_t offset, loff_t nbytes,
                unsigned int flags)
{
    int ret;
    struct fd f;
    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_CACHE_SHIFT)) {
            /*
             * The range starts outside a 32 bit machine's
             * pagecache addressing capabilities.  Let it "succeed"
             */
            ret = 0;
            goto out;
        }
        if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
            /*
             * Out to EOF
             */
            nbytes = 0;
        }
    }

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

    ret = -EBADF;
    f = fdget(fd);
    if (!f.file)
        goto out;

    i_mode = f.file->f_path.dentry->d_inode->i_mode;
    ret = -ESPIPE;
    if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
            !S_ISLNK(i_mode))
        goto out_put;

    mapping = f.file->f_mapping;
    if (!mapping) {
        ret = -EINVAL;
        goto out_put;
    }

    ret = 0;
    if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
        ret = filemap_fdatawait_range(mapping, offset, endbyte);
        if (ret < 0)
            goto out_put;
    }

    if (flags & SYNC_FILE_RANGE_WRITE) {
        ret = filemap_fdatawrite_range(mapping, offset, endbyte);
        if (ret < 0)
            goto out_put;
    }

    if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
        ret = filemap_fdatawait_range(mapping, offset, endbyte);

out_put:
    fdput(f);
out:
    return ret;
}
#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
asmlinkage long SyS_sync_file_range(long fd, loff_t offset, loff_t nbytes,
                    long flags)
{
    return SYSC_sync_file_range((int) fd, offset, nbytes,
                    (unsigned int) flags);
}
SYSCALL_ALIAS(sys_sync_file_range, SyS_sync_file_range);
#endif

/* It would be nice if people remember that not all the world's an i386
   when they introduce new system calls */
SYSCALL_DEFINE(sync_file_range2)(int fd, unsigned int flags,
                 loff_t offset, loff_t nbytes)
{
    return sys_sync_file_range(fd, offset, nbytes, flags);
}
#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
asmlinkage long SyS_sync_file_range2(long fd, long flags,
                     loff_t offset, loff_t nbytes)
{
    return SYSC_sync_file_range2((int) fd, (unsigned int) flags,
                     offset, nbytes);
}
SYSCALL_ALIAS(sys_sync_file_range2, SyS_sync_file_range2);
#endif