file.c

Go to the documentation of this file.

/*
 * fs/logfs/file.c  - prepare_write, commit_write and friends
 *
 * As should be obvious for Linux kernel code, license is GPLv2
 *
 * Copyright (c) 2005-2008 Joern Engel <[email protected]>
 */
#include "logfs.h"
#include <linux/sched.h>
#include <linux/writeback.h>

static int logfs_write_begin(struct file *file, struct address_space *mapping,
        loff_t pos, unsigned len, unsigned flags,
        struct page **pagep, void **fsdata)
{
    struct inode *inode = mapping->host;
    struct page *page;
    pgoff_t index = pos >> PAGE_CACHE_SHIFT;

    page = grab_cache_page_write_begin(mapping, index, flags);
    if (!page)
        return -ENOMEM;
    *pagep = page;

    if ((len == PAGE_CACHE_SIZE) || PageUptodate(page))
        return 0;
    if ((pos & PAGE_CACHE_MASK) >= i_size_read(inode)) {
        unsigned start = pos & (PAGE_CACHE_SIZE - 1);
        unsigned end = start + len;

        /* Reading beyond i_size is simple: memset to zero */
        zero_user_segments(page, 0, start, end, PAGE_CACHE_SIZE);
        return 0;
    }
    return logfs_readpage_nolock(page);
}

static int logfs_write_end(struct file *file, struct address_space *mapping,
        loff_t pos, unsigned len, unsigned copied, struct page *page,
        void *fsdata)
{
    struct inode *inode = mapping->host;
    pgoff_t index = page->index;
    unsigned start = pos & (PAGE_CACHE_SIZE - 1);
    unsigned end = start + copied;
    int ret = 0;

    BUG_ON(PAGE_CACHE_SIZE != inode->i_sb->s_blocksize);
    BUG_ON(page->index > I3_BLOCKS);

    if (copied < len) {
        /*
         * Short write of a non-initialized paged.  Just tell userspace
         * to retry the entire page.
         */
        if (!PageUptodate(page)) {
            copied = 0;
            goto out;
        }
    }
    if (copied == 0)
        goto out; /* FIXME: do we need to update inode? */

    if (i_size_read(inode) < (index << PAGE_CACHE_SHIFT) + end) {
        i_size_write(inode, (index << PAGE_CACHE_SHIFT) + end);
        mark_inode_dirty_sync(inode);
    }

    SetPageUptodate(page);
    if (!PageDirty(page)) {
        if (!get_page_reserve(inode, page))
            __set_page_dirty_nobuffers(page);
        else
            ret = logfs_write_buf(inode, page, WF_LOCK);
    }
out:
    unlock_page(page);
    page_cache_release(page);
    return ret ? ret : copied;
}

int logfs_readpage(struct file *file, struct page *page)
{
    int ret;

    ret = logfs_readpage_nolock(page);
    unlock_page(page);
    return ret;
}

/* Clear the page's dirty flag in the radix tree. */
/* TODO: mucking with PageWriteback is silly.  Add a generic function to clear
 * the dirty bit from the radix tree for filesystems that don't have to wait
 * for page writeback to finish (i.e. any compressing filesystem).
 */
static void clear_radix_tree_dirty(struct page *page)
{
    BUG_ON(PagePrivate(page) || page->private);
    set_page_writeback(page);
    end_page_writeback(page);
}

static int __logfs_writepage(struct page *page)
{
    struct inode *inode = page->mapping->host;
    int err;

    err = logfs_write_buf(inode, page, WF_LOCK);
    if (err)
        set_page_dirty(page);
    else
        clear_radix_tree_dirty(page);
    unlock_page(page);
    return err;
}

static int logfs_writepage(struct page *page, struct writeback_control *wbc)
{
    struct inode *inode = page->mapping->host;
    loff_t i_size = i_size_read(inode);
    pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
    unsigned offset;
    u64 bix;
    level_t level;

    log_file("logfs_writepage(%lx, %lx, %p)\n", inode->i_ino, page->index,
            page);

    logfs_unpack_index(page->index, &bix, &level);

    /* Indirect blocks are never truncated */
    if (level != 0)
        return __logfs_writepage(page);

    /*
     * TODO: everything below is a near-verbatim copy of nobh_writepage().
     * The relevant bits should be factored out after logfs is merged.
     */

    /* Is the page fully inside i_size? */
    if (bix < end_index)
        return __logfs_writepage(page);

     /* Is the page fully outside i_size? (truncate in progress) */
    offset = i_size & (PAGE_CACHE_SIZE-1);
    if (bix > end_index || offset == 0) {
        unlock_page(page);
        return 0; /* don't care */
    }

    /*
     * The page straddles i_size.  It must be zeroed out on each and every
     * writepage invokation because it may be mmapped.  "A file is mapped
     * in multiples of the page size.  For a file that is not a multiple of
     * the  page size, the remaining memory is zeroed when mapped, and
     * writes to that region are not written out to the file."
     */
    zero_user_segment(page, offset, PAGE_CACHE_SIZE);
    return __logfs_writepage(page);
}

static void logfs_invalidatepage(struct page *page, unsigned long offset)
{
    struct logfs_block *block = logfs_block(page);

    if (block->reserved_bytes) {
        struct super_block *sb = page->mapping->host->i_sb;
        struct logfs_super *super = logfs_super(sb);

        super->s_dirty_pages -= block->reserved_bytes;
        block->ops->free_block(sb, block);
        BUG_ON(bitmap_weight(block->alias_map, LOGFS_BLOCK_FACTOR));
    } else
        move_page_to_btree(page);
    BUG_ON(PagePrivate(page) || page->private);
}

static int logfs_releasepage(struct page *page, gfp_t only_xfs_uses_this)
{
    return 0; /* None of these are easy to release */
}


long logfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    struct inode *inode = file->f_path.dentry->d_inode;
    struct logfs_inode *li = logfs_inode(inode);
    unsigned int oldflags, flags;
    int err;

    switch (cmd) {
    case FS_IOC_GETFLAGS:
        flags = li->li_flags & LOGFS_FL_USER_VISIBLE;
        return put_user(flags, (int __user *)arg);
    case FS_IOC_SETFLAGS:
        if (IS_RDONLY(inode))
            return -EROFS;

        if (!inode_owner_or_capable(inode))
            return -EACCES;

        err = get_user(flags, (int __user *)arg);
        if (err)
            return err;

        mutex_lock(&inode->i_mutex);
        oldflags = li->li_flags;
        flags &= LOGFS_FL_USER_MODIFIABLE;
        flags |= oldflags & ~LOGFS_FL_USER_MODIFIABLE;
        li->li_flags = flags;
        mutex_unlock(&inode->i_mutex);

        inode->i_ctime = CURRENT_TIME;
        mark_inode_dirty_sync(inode);
        return 0;

    default:
        return -ENOTTY;
    }
}

int logfs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
{
    struct super_block *sb = file->f_mapping->host->i_sb;
    struct inode *inode = file->f_mapping->host;
    int ret;

    ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
    if (ret)
        return ret;

    mutex_lock(&inode->i_mutex);
    logfs_get_wblocks(sb, NULL, WF_LOCK);
    logfs_write_anchor(sb);
    logfs_put_wblocks(sb, NULL, WF_LOCK);
    mutex_unlock(&inode->i_mutex);

    return 0;
}

static int logfs_setattr(struct dentry *dentry, struct iattr *attr)
{
    struct inode *inode = dentry->d_inode;
    int err = 0;

    err = inode_change_ok(inode, attr);
    if (err)
        return err;

    if (attr->ia_valid & ATTR_SIZE) {
        err = logfs_truncate(inode, attr->ia_size);
        if (err)
            return err;
    }

    setattr_copy(inode, attr);
    mark_inode_dirty(inode);
    return 0;
}

const struct inode_operations logfs_reg_iops = {
    .setattr    = logfs_setattr,
};

const struct file_operations logfs_reg_fops = {
    .aio_read   = generic_file_aio_read,
    .aio_write  = generic_file_aio_write,
    .fsync      = logfs_fsync,
    .unlocked_ioctl = logfs_ioctl,
    .llseek     = generic_file_llseek,
    .mmap       = generic_file_readonly_mmap,
    .open       = generic_file_open,
    .read       = do_sync_read,
    .write      = do_sync_write,
};

const struct address_space_operations logfs_reg_aops = {
    .invalidatepage = logfs_invalidatepage,
    .readpage   = logfs_readpage,
    .releasepage    = logfs_releasepage,
    .set_page_dirty = __set_page_dirty_nobuffers,
    .writepage  = logfs_writepage,
    .writepages = generic_writepages,
    .write_begin    = logfs_write_begin,
    .write_end  = logfs_write_end,
};