[PATCH 6/17] [LogFS] file.c

Joern Engel
2009-11-20T20:25:00Z

---
fs/logfs/file.c | 263 ++++

diff --git a/fs/logfs/file.c b/fs/logfs/file.c
new file mode 100644
index 0000000..370f367
--- /dev/null
+++ b/fs/logfs/file.c
@@ -0,0 +1,263 @@
+/*
+ * 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 <joern@logfs.org>
+ */
+#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)
+{
+ 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 */
+}
+
+
+int logfs_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
+ unsigned long arg)
+{
+ 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 (!is_owner_or_cap(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, struct dentry *dentry, int datasync)
+{
+ struct super_block *sb = dentry->d_inode->i_sb;
+ struct logfs_super *super = logfs_super(sb);
+
+ /* FIXME: write anchor */
+ super->s_devops->sync(sb);
+ return 0;
+}
+
+static int logfs_setattr(struct dentry *dentry, struct iattr *attr)
+{
+ struct inode *inode = dentry->d_inode;
+ int err = 0;
+
+ if (attr->ia_valid & ATTR_SIZE)
+ err = logfs_truncate(inode, attr->ia_size);
+ attr->ia_valid &= ~ATTR_SIZE;
+
+ if (!err)
+ err = inode_change_ok(inode, attr);
+ if (!err)
+ err = inode_setattr(inode, attr);
+ return err;
+}
+
+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,
+ .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,
+};