quota.html

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  67 <h1 class="title">quota</h1>
  68
  69
  70 <div id="table-of-contents">
  71 <h2>Table of Contents</h2>
  72 <div id="text-table-of-contents">
  73 <ul>
  74 <li><a href="#sec-1">1 directory tree quota design and implementation </a>
  75 <ul>
  76 <li><a href="#sec-1.1">1.1 STATUS </a></li>
  77 <li><a href="#sec-1.2">1.2 Introduction </a></li>
  78 <li><a href="#sec-1.3">1.3 Containers fs root requirement </a></li>
  79 <li><a href="#sec-1.4">1.4 Containers directory tree-id  assumptions </a>
  80 <ul>
  81 <li><a href="#sec-1.4.1">1.4.1 -&gt;rename() restriction </a></li>
  82 <li><a href="#sec-1.4.2">1.4.2 -&gt;link restriction </a></li>
  83 </ul>
  84 </li>
  85 <li><a href="#sec-1.5">1.5 Patch queue </a></li>
  86 <li><a href="#sec-1.6">1.6 How-to </a>
  87 <ul>
  88 <li><a href="#sec-1.6.1">1.6.1 Enabling tree quota an Easy way </a></li>
  89 <li><a href="#sec-1.6.2">1.6.2 Enabling tree quota from very beginning </a></li>
  90 <li><a href="#sec-1.6.3">1.6.3 Creating containers tree </a></li>
  91 </ul>
  92 </li>
  93 </ul>
  94 </li>
  95 </ul>
  96 </div>
  97 </div>
  98
  99 <div id="outline-container-1" class="outline-2">
 100 <h2 id="sec-1">1 directory tree quota design and implementation </h2>
 101 <div id="text-1">
 102
 103
 104 </div>
 105
 106 <div id="outline-container-1.1" class="outline-3">
 107 <h3 id="sec-1.1">1.1 STATUS </h3>
 108 <div id="text-1.1">
 109
 110 <p>V0.07 :: I've succeed in testing journalled tree-quota. At least it survived
 111 in fsstress and other manual tests.
 112 </p>
 113 </div>
 114
 115 </div>
 116
 117 <div id="outline-container-1.2" class="outline-3">
 118 <h3 id="sec-1.2">1.2 Introduction </h3>
 119 <div id="text-1.2">
 120
 121 <p>This document contains basic introduction to directory tree
 122 quota for dedicated trees. Currently Linux support many
 123 virtualization extensions. One of approaches is containers.
 124 Containers is OS level paravirtualization like jail in BSD.
 125 In two words container is a set of process isolated from
 126 other system. Each process has it's own name-spaces for
 127 network,fs,ipc,etc. You may think of container as secure chroot.
 128 </p>
 129 </div>
 130
 131 </div>
 132
 133 <div id="outline-container-1.3" class="outline-3">
 134 <h3 id="sec-1.3">1.3 Containers fs root requirement </h3>
 135 <div id="text-1.3">
 136
 137 <p>Container's root are independent tree or several trees.
 138 usually they organized like follows <b>/ct-root/CT${ID\}/${tree-content}</b>
 139 There are many reasons to keep this trees separate one from another
 140 </p><dl>
 141 <dt>inode attr</dt><dd>
 142
 143 <p>
 144 If inode has links in A and B trees. And A-user call chown() for
 145 this inode, then B's owner will be surprised.
 146 The only way to overcome this is to virtualize inode attributes
 147 (for each tree) which is madness IMHO.
 148 </p></dd>
 149 <dt>checkpoint/restore/online-backup</dt><dd>
 150
 151 <p>
 152 This is like suspend resume for VM, but in this case only
 153 container's process are stopped(freezed) for some time. After CT's
 154 process are stopped we may create backup CT's tree without freezing
 155 FS as a whole.
 156 </p>
 157 </dd>
 158 </dl>
 159
 160 <p>As I already say there are many way to isolate per-container fs-tree.
 161 But everyone has strong disadvantages:
 162 </p><dl>
 163 <dt>Virtual block devices(qemu-like)</dt><dd>
 164 problems with consistency and performance
 165 </dd>
 166 <dt>ext3/4 + stack-fs(unionfs)</dt><dd>
 167 Bad failure resistance. It is impossible to support jorunalling quota file on stack-fs level.
 168 </dd>
 169 <dt>XFS with proj quota</dt><dd>
 170 Lack of quota file journalling.
 171
 172 </dd>
 173 </dl>
 174
 175 <p>So the only way to implement journalled quota for containers is to
 176 implement it on native fs level.
 177 </p>
 178 </div>
 179
 180 </div>
 181
 182 <div id="outline-container-1.4" class="outline-3">
 183 <h3 id="sec-1.4">1.4 Containers directory tree-id  assumptions </h3>
 184 <div id="text-1.4">
 185
 186 <ol>
 187 <li>
 188 Tree id is embedded inside inode
 189 </li>
 190 <li>
 191 Tree id is inherent from parent dir
 192 </li>
 193 <li>
 194 Inode can not belongs to different directory trees
 195
 196 </li>
 197 </ol>
 198
 199 <p>Default directory tree (with id == 0) has special meaning.
 200 directory which belongs to default tree may contains roots of
 201 other trees. Default tree is used for subtree manipulation.
 202 </p>
 203 </div>
 204
 205 <div id="outline-container-1.4.1" class="outline-4">
 206 <h4 id="sec-1.4.1">1.4.1 -&gt;rename() restriction </h4>
 207 <div id="text-1.4.1">
 208
 209
 210
 211
 212 <pre class="example">
 213   if (S_ISDIR(old_inode-&gt;i_mode)) {
 214       if ((new_dir-&gt;i_tree_id == 0) || /* move to default tree */
 215                (new_dir-&gt;i_tree_id == old_inode-&gt;i_tree_id)) /*same tree */
 216              goto good;
 217       return -EXDEV;
 218   } else {
 219       /* If entry have more than one link then it is bad idea to allow
 220          rename it to different (even if it's default tree) tree,
 221          because this result in rule (3) violation.
 222        */
 223       if (old_inode-&gt;i_nlink &gt; 1) &amp;&amp;
 224                     (new_dir-&gt;i_tree_id != old_inode-&gt;i_tree_id)
 225             return -EXDEV;
 226  }
 227 </pre>
 228
 229
 230
 231
 232 </div>
 233
 234 </div>
 235
 236 <div id="outline-container-1.4.2" class="outline-4">
 237 <h4 id="sec-1.4.2">1.4.2 -&gt;link restriction </h4>
 238 <div id="text-1.4.2">
 239
 240
 241
 242
 243 <pre class="example">
 244    /* Links may  belongs to only one tree */
 245    if(new_dir-&gt;i_tree_id != old_inode-&gt;i_tree_id)
 246             return -EXDEV;
 247 </pre>
 248
 249
 250
 251 </div>
 252 </div>
 253
 254 </div>
 255
 256 <div id="outline-container-1.5" class="outline-3">
 257 <h3 id="sec-1.5">1.5 Patch queue </h3>
 258 <div id="text-1.5">
 259
 260 <p>I've prepare proof of concept patch queue.
 261 <a href="http://www.2ka.mipt.ru/~mov/tree-quota.tgz">patch-queue</a>
 262 </p></div>
 263
 264 </div>
 265
 266 <div id="outline-container-1.6" class="outline-3">
 267 <h3 id="sec-1.6">1.6 How-to </h3>
 268 <div id="text-1.6">
 269
 270 <p>This part contain some tips of tree-quota usage. Assume you have kernel
 271 with tree-quota patch applied.
 272 </p>
 273 </div>
 274
 275 <div id="outline-container-1.6.1" class="outline-4">
 276 <h4 id="sec-1.6.1">1.6.1 Enabling tree quota an Easy way </h4>
 277 <div id="text-1.6.1">
 278
 279 <p>You may download small file-system image with tree-quota enabled.
 280 <a href="http://www.2ka.mipt.ru/~mov/fs-trquota.img.gz">fs-trquota.img.gz(3Mb)</a>
 281 mount /test/fs.img /mnt -oloop,quota,grpquota,treeid,trquota
 282 <b>NOTE in order to use journalling quota use following mount options</b>
 283 </p>
 284
 285
 286 <pre class="example">
 287    jqfmt=vfsv0,treeid,trjquota=aquota.tree
 288 </pre>
 289
 290
 291
 292
 293 <pre class="example">
 294     Currently quota-tools has no tree-quota support. So you have to manually
 295     create aquota.tree file. Just copy quota-tree/tool/aquota.tree to the root
 296     of your fs
 297     mount /test/fs.img /mnt -oloop,quota,grpquota,treeid,trquota
 298     cp quota-tree/tool/aquota.tree  /mnt/
 299     # enable all quotas
 300     quota-tree/tool/quotactl --on --all --path /mnt --dev /dev/loop0
 301     # show quotas type ==0 -&gt; usrquota, type == 2 -&gt; trqota
 302     quota-tree/tool/quotactl --get --all --type 2 --dev /dev/loop0
 303 </pre>
 304
 305
 306
 307 </div>
 308
 309 </div>
 310
 311 <div id="outline-container-1.6.2" class="outline-4">
 312 <h4 id="sec-1.6.2">1.6.2 Enabling tree quota from very beginning </h4>
 313 <div id="text-1.6.2">
 314
 315
 316
 317
 318 <pre class="example">
 319     Currently quota-tools has no tree-quota support. So you have to manually
 320     create aquota.tree file. Just copy quota-tree/tool/aquota.tree to the root
 321     of your fs
 322     mount /test/fs.img /mnt -oloop,quota,grpquota,treeid,trquota
 323     cp quota-tree/tool/aquota.tree  /mnt/
 324     # enable all quotas
 325     quota-tree/tool/quotactl --on --all --path /mnt --dev /dev/loop0
 326     # show quotas type ==0 -&gt; usrquota, type == 2 -&gt; trqota
 327     quota-tree/tool/quotactl --get --all --type 2 --dev /dev/loop0
 328 </pre>
 329
 330
 331
 332 </div>
 333
 334 </div>
 335
 336 <div id="outline-container-1.6.3" class="outline-4">
 337 <h4 id="sec-1.6.3">1.6.3 Creating containers tree </h4>
 338 <div id="text-1.6.3">
 339
 340
 341
 342
 343 <pre class="example">
 344     # create root dir for directory-tree
 345     mkdir /mnt/ct-root-1
 346     # Assign id for the root
 347     ./chattr -Q 1 /mnt/ct-root-1
 348     # set quota limits for tree
 349     quota-tree/tool/quotactl --set --type 2 --id 1 --bsoft 100000 --bhard 110000 --dev /dev/loop0
 350     # show quotas
 351     quota-tree/tool/quotactl --get --all --type 2 --dev /dev/loop0
 352     # Populate root with content, it will be accounted in to
 353     # tree-quota with id "1"
 354     tar zxf root.tar -C /mnt/ct-root-1
 355     # show quotas
 356     quota-tree/tool/quotactl --get --all --type 2 --dev /dev/loop0
 357 </pre>
 358
 359
 360
 361 </div>
 362 </div>
 363 </div>
 364 </div>
 365 <div id="postamble"><p class="author"> Author: Monahov Dmitry
 366 <a href="mailto:mov@jazz.campus">&lt;mov@jazz.campus&gt;</a>
 367 </p>
 368 <p class="date"> Date: 2009-11-19 18:21:17 MSK</p>
 369 <p>HTML generated by org-mode 6.21b in emacs 23</p>
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