fs/logfs/file.c

   1 /*
   2  * fs/logfs/file.c      - prepare_write, commit_write and friends
   3  *
   4  * As should be obvious for Linux kernel code, license is GPLv2
   5  *
   6  * Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
   7  */
   8 #include "logfs.h"
   9 #include <linux/sched.h>
  10 #include <linux/writeback.h>
  11
  12 static int logfs_write_begin(struct file *file, struct address_space *mapping,
  13                 loff_t pos, unsigned len, unsigned flags,
  14                 struct page **pagep, void **fsdata)
  15 {
  16         struct inode *inode = mapping->host;
  17         struct page *page;
  18         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
  19
  20         page = grab_cache_page_write_begin(mapping, index, flags);
  21         if (!page)
  22                 return -ENOMEM;
  23         *pagep = page;
  24
  25         if ((len == PAGE_CACHE_SIZE) || PageUptodate(page))
  26                 return 0;
  27         if ((pos & PAGE_CACHE_MASK) >= i_size_read(inode)) {
  28                 unsigned start = pos & (PAGE_CACHE_SIZE - 1);
  29                 unsigned end = start + len;
  30
  31                 /* Reading beyond i_size is simple: memset to zero */
  32                 zero_user_segments(page, 0, start, end, PAGE_CACHE_SIZE);
  33                 return 0;
  34         }
  35         return logfs_readpage_nolock(page);
  36 }
  37
  38 static int logfs_write_end(struct file *file, struct address_space *mapping,
  39                 loff_t pos, unsigned len, unsigned copied, struct page *page,
  40                 void *fsdata)
  41 {
  42         struct inode *inode = mapping->host;
  43         pgoff_t index = page->index;
  44         unsigned start = pos & (PAGE_CACHE_SIZE - 1);
  45         unsigned end = start + copied;
  46         int ret = 0;
  47
  48         BUG_ON(PAGE_CACHE_SIZE != inode->i_sb->s_blocksize);
  49         BUG_ON(page->index > I3_BLOCKS);
  50
  51         if (copied < len) {
  52                 /*
  53                  * Short write of a non-initialized paged.  Just tell userspace
  54                  * to retry the entire page.
  55                  */
  56                 if (!PageUptodate(page)) {
  57                         copied = 0;
  58                         goto out;
  59                 }
  60         }
  61         if (copied == 0)
  62                 goto out; /* FIXME: do we need to update inode? */
  63
  64         if (i_size_read(inode) < (index << PAGE_CACHE_SHIFT) + end) {
  65                 i_size_write(inode, (index << PAGE_CACHE_SHIFT) + end);
  66                 mark_inode_dirty_sync(inode);
  67         }
  68
  69         SetPageUptodate(page);
  70         if (!PageDirty(page)) {
  71                 if (!get_page_reserve(inode, page))
  72                         __set_page_dirty_nobuffers(page);
  73                 else
  74                         ret = logfs_write_buf(inode, page, WF_LOCK);
  75         }
  76 out:
  77         unlock_page(page);
  78         page_cache_release(page);
  79         return ret ? ret : copied;
  80 }
  81
  82 int logfs_readpage(struct file *file, struct page *page)
  83 {
  84         int ret;
  85
  86         ret = logfs_readpage_nolock(page);
  87         unlock_page(page);
  88         return ret;
  89 }
  90
  91 /* Clear the page's dirty flag in the radix tree. */
  92 /* TODO: mucking with PageWriteback is silly.  Add a generic function to clear
  93  * the dirty bit from the radix tree for filesystems that don't have to wait
  94  * for page writeback to finish (i.e. any compressing filesystem).
  95  */
  96 static void clear_radix_tree_dirty(struct page *page)
  97 {
  98         BUG_ON(PagePrivate(page) || page->private);
  99         set_page_writeback(page);
 100         end_page_writeback(page);
 101 }
 102
 103 static int __logfs_writepage(struct page *page)
 104 {
 105         struct inode *inode = page->mapping->host;
 106         int err;
 107
 108         err = logfs_write_buf(inode, page, WF_LOCK);
 109         if (err)
 110                 set_page_dirty(page);
 111         else
 112                 clear_radix_tree_dirty(page);
 113         unlock_page(page);
 114         return err;
 115 }
 116
 117 static int logfs_writepage(struct page *page, struct writeback_control *wbc)
 118 {
 119         struct inode *inode = page->mapping->host;
 120         loff_t i_size = i_size_read(inode);
 121         pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
 122         unsigned offset;
 123         u64 bix;
 124         level_t level;
 125
 126         log_file("logfs_writepage(%lx, %lx, %p)\n", inode->i_ino, page->index,
 127                         page);
 128
 129         logfs_unpack_index(page->index, &bix, &level);
 130
 131         /* Indirect blocks are never truncated */
 132         if (level != 0)
 133                 return __logfs_writepage(page);
 134
 135         /*
 136          * TODO: everything below is a near-verbatim copy of nobh_writepage().
 137          * The relevant bits should be factored out after logfs is merged.
 138          */
 139
 140         /* Is the page fully inside i_size? */
 141         if (bix < end_index)
 142                 return __logfs_writepage(page);
 143
 144          /* Is the page fully outside i_size? (truncate in progress) */
 145         offset = i_size & (PAGE_CACHE_SIZE-1);
 146         if (bix > end_index || offset == 0) {
 147                 unlock_page(page);
 148                 return 0; /* don't care */
 149         }
 150
 151         /*
 152          * The page straddles i_size.  It must be zeroed out on each and every
 153          * writepage invokation because it may be mmapped.  "A file is mapped
 154          * in multiples of the page size.  For a file that is not a multiple of
 155          * the  page size, the remaining memory is zeroed when mapped, and
 156          * writes to that region are not written out to the file."
 157          */
 158         zero_user_segment(page, offset, PAGE_CACHE_SIZE);
 159         return __logfs_writepage(page);
 160 }
 161
 162 static void logfs_invalidatepage(struct page *page, unsigned long offset)
 163 {
 164         struct logfs_block *block = logfs_block(page);
 165
 166         if (block->reserved_bytes) {
 167                 struct super_block *sb = page->mapping->host->i_sb;
 168                 struct logfs_super *super = logfs_super(sb);
 169
 170                 super->s_dirty_pages -= block->reserved_bytes;
 171                 block->ops->free_block(sb, block);
 172                 BUG_ON(bitmap_weight(block->alias_map, LOGFS_BLOCK_FACTOR));
 173         } else
 174                 move_page_to_btree(page);
 175         BUG_ON(PagePrivate(page) || page->private);
 176 }
 177
 178 static int logfs_releasepage(struct page *page, gfp_t only_xfs_uses_this)
 179 {
 180         return 0; /* None of these are easy to release */
 181 }
 182
 183
 184 long logfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 185 {
 186         struct inode *inode = file->f_path.dentry->d_inode;
 187         struct logfs_inode *li = logfs_inode(inode);
 188         unsigned int oldflags, flags;
 189         int err;
 190
 191         switch (cmd) {
 192         case FS_IOC_GETFLAGS:
 193                 flags = li->li_flags & LOGFS_FL_USER_VISIBLE;
 194                 return put_user(flags, (int __user *)arg);
 195         case FS_IOC_SETFLAGS:
 196                 if (IS_RDONLY(inode))
 197                         return -EROFS;
 198
 199                 if (!is_owner_or_cap(inode))
 200                         return -EACCES;
 201
 202                 err = get_user(flags, (int __user *)arg);
 203                 if (err)
 204                         return err;
 205
 206                 mutex_lock(&inode->i_mutex);
 207                 oldflags = li->li_flags;
 208                 flags &= LOGFS_FL_USER_MODIFIABLE;
 209                 flags |= oldflags & ~LOGFS_FL_USER_MODIFIABLE;
 210                 li->li_flags = flags;
 211                 mutex_unlock(&inode->i_mutex);
 212
 213                 inode->i_ctime = CURRENT_TIME;
 214                 mark_inode_dirty_sync(inode);
 215                 return 0;
 216
 217         default:
 218                 return -ENOTTY;
 219         }
 220 }
 221
 222 int logfs_fsync(struct file *file, int datasync)
 223 {
 224         struct super_block *sb = file->f_mapping->host->i_sb;
 225
 226         logfs_write_anchor(sb);
 227         return 0;
 228 }
 229
 230 static int logfs_setattr(struct dentry *dentry, struct iattr *attr)
 231 {
 232         struct inode *inode = dentry->d_inode;
 233         int err = 0;
 234
 235         err = inode_change_ok(inode, attr);
 236         if (err)
 237                 return err;
 238
 239         if (attr->ia_valid & ATTR_SIZE) {
 240                 err = logfs_truncate(inode, attr->ia_size);
 241                 if (err)
 242                         return err;
 243         }
 244
 245         setattr_copy(inode, attr);
 246         mark_inode_dirty(inode);
 247         return 0;
 248 }
 249
 250 const struct inode_operations logfs_reg_iops = {
 251         .setattr        = logfs_setattr,
 252 };
 253
 254 const struct file_operations logfs_reg_fops = {
 255         .aio_read       = generic_file_aio_read,
 256         .aio_write      = generic_file_aio_write,
 257         .fsync          = logfs_fsync,
 258         .unlocked_ioctl = logfs_ioctl,
 259         .llseek         = generic_file_llseek,
 260         .mmap           = generic_file_readonly_mmap,
 261         .open           = generic_file_open,
 262         .read           = do_sync_read,
 263         .write          = do_sync_write,
 264 };
 265
 266 const struct address_space_operations logfs_reg_aops = {
 267         .invalidatepage = logfs_invalidatepage,
 268         .readpage       = logfs_readpage,
 269         .releasepage    = logfs_releasepage,
 270         .set_page_dirty = __set_page_dirty_nobuffers,
 271         .writepage      = logfs_writepage,
 272         .writepages     = generic_writepages,
 273         .write_begin    = logfs_write_begin,
 274         .write_end      = logfs_write_end,
 275 };