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  1. 10 Feb, 2020 8 commits
    • Bob Peterson's avatar
      gfs2: Rework how rgrp buffer_heads are managed · b3422cac
      Bob Peterson authored 
      Before this patch, the rgrp code had a serious problem related to
how it managed buffer_heads for resource groups. The problem caused
file system corruption, especially in cases of journal replay.

When an rgrp glock was demoted to transfer ownership to a
different cluster node, do_xmote() first calls rgrp_go_sync and then
rgrp_go_inval, as expected. When it calls rgrp_go_sync, that called
gfs2_rgrp_brelse() that dropped the buffer_head reference count.
In most cases, the reference count went to zero, which is right.
However, there were other places where the buffers are handled
differently.

After rgrp_go_sync, do_xmote called rgrp_go_inval which called
gfs2_rgrp_brelse a second time, then rgrp_go_inval's call to
truncate_inode_pages_range would get rid of the pages in memory,
but only if the reference count drops to 0.

Unfortunately, gfs2_rgrp_brelse was setting bi->bi_bh = NULL.
So when rgrp_go_sync called gfs2_rgrp_brelse, it lost the pointer
to the buffer_heads in cases where the reference count was still 1.
Therefore, when rgrp_go_inval called gfs2_rgrp_brelse a second time,
it failed the check for "if (bi->bi_bh)" and thus failed to call
brelse a second time. Because of that, the reference count on those
buffers sometimes failed to drop from 1 to 0. And that caused
function truncate_inode_pages_range to keep the pages in page cache
rather than freeing them.

The next time the rgrp glock was acquired, the metadata read of
the rgrp buffers re-used the pages in memory, which were now
wrong because they were likely modified by the other node who
acquired the glock in EX (which is why we demoted the glock).
This re-use of the page cache caused corruption because changes
made by the other nodes were never seen, so the bitmaps were
inaccurate.

For some reason, the problem became most apparent when journal
replay forced the replay of rgrps in memory, which caused newer
rgrp data to be overwritten by the older in-core pages.

A big part of the problem was that the rgrp buffer were released
in multiple places: The go_unlock function would release them when
the glock was released rather than when the glock is demoted,
which is clearly wrong because our intent was to cache them until
the glock is demoted from SH or EX.

This patch attempts to clean up the mess and make one consistent
and centralized mechanism for managing the rgrp buffer_heads by
implementing several changes:

1. It eliminates the call to gfs2_rgrp_brelse() from rgrp_go_sync.
   We don't want to release the buffers or zero the pointers when
   syncing for the reasons stated above. It only makes sense to
   release them when the glock is actually invalidated (go_inval).
   And when we do, then we set the bh pointers to NULL.
2. The go_unlock function (which was only used for rgrps) is
   eliminated, as we've talked about doing many times before.
   The go_unlock function was called too early in the glock dq
   process, and should not happen until the glock is invalidated.
3. It also eliminates the call to rgrp_brelse in gfs2_clear_rgrpd.
   That will now happen automatically when the rgrp glocks are
   demoted, and shouldn't happen any sooner or later than that.
   Instead, function gfs2_clear_rgrpd has been modified to demote
   the rgrp glocks, and therefore, free those pages, before the
   remaining glocks are culled by gfs2_gl_hash_clear. This
   prevents the gl_object from hanging around when the glocks are
   culled.
Signed-off-by: default avatarBob Peterson <rpeterso@redhat.com>
Reviewed-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
      b3422cac
    • Bob Peterson's avatar
      gfs2: clear ail1 list when gfs2 withdraws · 30fe70a8
      Bob Peterson authored 
      This patch fixes a bug in which function gfs2_log_flush can get into
an infinite loop when a gfs2 file system is withdrawn. The problem
is the infinite loop "for (;;)" in gfs2_log_flush which would never
finish because the io error and subsequent withdraw prevented the
items from being taken off the ail list.

This patch tries to clean up the mess by allowing withdraw situations
to move not-in-flight buffer_heads to the ail2 list, where they will
be dealt with later.
Signed-off-by: default avatarBob Peterson <rpeterso@redhat.com>
Reviewed-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
      30fe70a8
    • Bob Peterson's avatar
      gfs2: Introduce concept of a pending withdraw · 69511080
      Bob Peterson authored 
      File system withdraws can be delayed when inconsistencies are
discovered when we cannot withdraw immediately, for example, when
critical spin_locks are held. But delaying the withdraw can cause
gfs2 to ignore the error and keep running for a short period of time.
For example, an rgrp glock may be dequeued and demoted while there
are still buffers that haven't been properly revoked, due to io
errors writing to the journal.

This patch introduces a new concept of a pending withdraw, which
means an inconsistency has been discovered and we need to withdraw
at the earliest possible opportunity. In these cases, we aren't
quite withdrawn yet, but we still need to not dequeue glocks and
other critical things. If we dequeue the glocks and the withdraw
results in our journal being replayed, the replay could overwrite
data that's been modified by a different node that acquired the
glock in the meantime.
Signed-off-by: default avatarBob Peterson <rpeterso@redhat.com>
Reviewed-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
      69511080
    • Andreas Gruenbacher's avatar
      gfs2: Return bool from gfs2_assert functions · 8e28ef1f
      Andreas Gruenbacher authored 
      The gfs2_assert functions only print messages when the filesystem hasn't been
withdrawn yet, and they indicate whether or not they've printed something in
their return value.  However, none of the callers use that information, so
simply return whether or not the assert has failed.

(The gfs2_assert functions are still backwards; they return false when an
assertion is true.)
Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: default avatarBob Peterson <rpeterso@redhat.com>
      8e28ef1f
    • Andreas Gruenbacher's avatar
      gfs2: Turn gfs2_consist into void functions · a5ca2f1c
      Andreas Gruenbacher authored 
      Change the various gfs2_consist functions to return void.
Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: default avatarBob Peterson <rpeterso@redhat.com>
      a5ca2f1c
    • Andreas Gruenbacher's avatar
      gfs2: Remove usused cluster_wide arguments of gfs2_consist functions · d7e7ab3f
      Andreas Gruenbacher authored 
      These arguments are always passed as 0, and they are never evaluated.
Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: default avatarBob Peterson <rpeterso@redhat.com>
      d7e7ab3f
    • Andreas Gruenbacher's avatar
      gfs2: Report errors before withdraw · 8dc88ac6
      Andreas Gruenbacher authored 
      In gfs2_rgrp_verify and compute_bitstructs, make sure to report errors before
withdrawing the filesystem: otherwise, when we withdraw first and withdraw is
configured to panic, we'll never get to the error reporting.
Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: default avatarBob Peterson <rpeterso@redhat.com>
      8dc88ac6
    • Andreas Gruenbacher's avatar
      gfs2: Split gfs2_lm_withdraw into two functions · badb55ec
      Andreas Gruenbacher authored 
      Split gfs2_lm_withdraw into a function that prints an error message and a
function that withdraws the filesystem.
Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: default avatarBob Peterson <rpeterso@redhat.com>
      badb55ec
  3. 06 Feb, 2020 3 commits
  5. 31 Jan, 2020 29 commits
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