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authorArtem Bityutskiy <Artem.Bityutskiy@nokia.com>2011-04-25 18:17:09 +0300
committerGreg Kroah-Hartman <gregkh@suse.de>2011-05-09 15:06:39 -0700
commit21fb89793df408cc116aa52399a5e6f7af459596 (patch)
tree257b9e64479d83ef9c5d19a643ece07f1922f53e /drivers
parentb000ec13075615ace30250ab6e355a3f0c956735 (diff)
downloadlinux-linaro-android-21fb89793df408cc116aa52399a5e6f7af459596.tar.gz
UBIFS: do not free write-buffers when in R/O mode
commit b50b9f408502a2ea90459ae36ba8cdc9cc005cfe upstream. Currently UBIFS has a small optimization - it frees write-buffers when it is re-mounted from R/W mode to R/O mode. Of course, when it is mounted R/O, it does not allocate write-buffers as well. This optimization is nice but it leads to subtle problems and complications in recovery, which I can reproduce using the integck test. The symptoms are that after a power cut the file-system cannot be mounted if we first mount it R/O, and then re-mount R/W - 'ubifs_rcvry_gc_commit()' prints: UBIFS error (pid 34456): could not find an empty LEB Analysis of the problem. When mounting R/W, the reply process sets journal heads to buds [1], but when mounting R/O - it does not do this, because the write-buffers are not allocated. So 'ubifs_rcvry_gc_commit()' works completely differently for the same file-system but for the following 2 cases: 1. mounting R/W after a power cut and recover 2. mounting R/O after a power cut, re-mounting R/W and run deferred recovery In the former case, we have journal heads seeked to the a bud, in the latter case, they are non-seeked (wbuf->lnum == -1). So in the latter case we do not try to recover the GC LEB by garbage-collecting to the GC head, but we just try to find an empty LEB, and there may be no empty LEBs, so we just fail. On the other hand, in the former case (mount R/W), we are able to make a GC LEB (@c->gc_lnum) by garbage-collecting. Thus, let's remove this small nice optimization and always allocate write-buffers. This should not make too big difference - we have only 3 of them, each of max. write unit size, which is usually 2KiB. So this is about 6KiB of RAM for the typical case, and only when mounted R/O. [1]: Note, currently the replay process is setting (seeking) the journal heads to _some_ buds, not necessarily to the buds which had been the journal heads before the power cut happened. This will be fixed separately. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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