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Commit 4b06e5b9ad8abb20105b2b25e42c509ebe9b2d76

Authored by Jun'ichi Nomura
Committed by Al Viro
1 parent 8dd5ca532c
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

freeze_bdev: don't deactivate successfully frozen MS_RDONLY sb 

Thanks Thomas and Christoph for testing and review.
I removed 'smp_wmb()' before up_write from the previous patch,
since up_write() should have necessary ordering constraints.
(I.e. the change of s_frozen is visible to others after up_write)
I'm quite sure the change is harmless but if you are uncomfortable
with Tested-by/Reviewed-by on the modified patch, please remove them.

If MS_RDONLY, freeze_bdev should just up_write(s_umount) instead of
deactivate_locked_super().
Also, keep sb->s_frozen consistent so that remount can check the frozen state.

Otherwise a crash reported here can happen:
http://lkml.org/lkml/2010/1/16/37
http://lkml.org/lkml/2010/1/28/53

This patch should be applied for 2.6.32 stable series, too.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Thomas Backlund <tmb@mandriva.org>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: stable@kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Showing 1 changed file with 4 additions and 3 deletions Side-by-side Diff

... ... @@ -246,7 +246,8 @@
246 246 if (!sb)
247 247 goto out;
248 248 if (sb->s_flags & MS_RDONLY) {
249   - deactivate_locked_super(sb);
  249 + sb->s_frozen = SB_FREEZE_TRANS;
  250 + up_write(&sb->s_umount);
250 251 mutex_unlock(&bdev->bd_fsfreeze_mutex);
251 252 return sb;
252 253 }
... ... @@ -307,7 +308,7 @@
307 308 BUG_ON(sb->s_bdev != bdev);
308 309 down_write(&sb->s_umount);
309 310 if (sb->s_flags & MS_RDONLY)
310   - goto out_deactivate;
  311 + goto out_unfrozen;
311 312  
312 313 if (sb->s_op->unfreeze_fs) {
313 314 error = sb->s_op->unfreeze_fs(sb);
314 315  
... ... @@ -321,11 +322,11 @@
321 322 }
322 323 }
323 324  
  325 +out_unfrozen:
324 326 sb->s_frozen = SB_UNFROZEN;
325 327 smp_wmb();
326 328 wake_up(&sb->s_wait_unfrozen);
327 329  
328   -out_deactivate:
329 330 if (sb)
330 331 deactivate_locked_super(sb);
331 332 out_unlock: