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ceph: fix rdcache_gen usage and invalidate

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We used to use rdcache_gen to indicate whether we "might" have cached
pages.  Now we just look at the mapping to determine that.  However, some
old behavior remains from that transition.

First, rdcache_gen == 0 no longer means we have no pages.  That can happen
at any time (presumably when we carry FILE_CACHE).  We should not reset it
to zero, and we should not check that it is zero.

That means that the only purpose for rdcache_revoking is to resolve races
between new issues of FILE_CACHE and an async invalidate.  If they are
equal, we should invalidate.  On success, we decrement rdcache_revoking,
so that it is no longer equal to rdcache_gen.  Similarly, if we success
in doing a sync invalidate, set revoking = gen - 1.  (This is a small
optimization to avoid doing unnecessary invalidate work and does not
affect correctness.)

Signed-off-by: Sage Weil <sage@newdream.net>
This commit is contained in:
Sage Weil
2010-11-04 11:05:05 -07:00
parent feb4cc9bb4
commit cd045cb42a
3 changed files with 10 additions and 14 deletions
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16
fs/ceph/inode.c
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@@ -1394,11 +1394,8 @@ static void ceph_invalidate_work(struct work_struct *work)
spin_lock(&inode->i_lock);
dout("invalidate_pages %p gen %d revoking %d\n", inode,
ci->i_rdcache_gen, ci->i_rdcache_revoking);
if (ci->i_rdcache_gen == 0 ||
ci->i_rdcache_revoking != ci->i_rdcache_gen) {
BUG_ON(ci->i_rdcache_revoking > ci->i_rdcache_gen);
if (ci->i_rdcache_revoking != ci->i_rdcache_gen) {
/* nevermind! */
ci->i_rdcache_revoking = 0;
spin_unlock(&inode->i_lock);
goto out;
}
@@ -1408,15 +1405,16 @@ static void ceph_invalidate_work(struct work_struct *work)
ceph_invalidate_nondirty_pages(inode->i_mapping);
spin_lock(&inode->i_lock);
if (orig_gen == ci->i_rdcache_gen) {
if (orig_gen == ci->i_rdcache_gen &&
orig_gen == ci->i_rdcache_revoking) {
dout("invalidate_pages %p gen %d successful\n", inode,
ci->i_rdcache_gen);
ci->i_rdcache_gen = 0;
ci->i_rdcache_revoking = 0;
ci->i_rdcache_revoking--;
check = 1;
} else {
dout("invalidate_pages %p gen %d raced, gen now %d\n",
inode, orig_gen, ci->i_rdcache_gen);
dout("invalidate_pages %p gen %d raced, now %d revoking %d\n",
inode, orig_gen, ci->i_rdcache_gen,
ci->i_rdcache_revoking);
}
spin_unlock(&inode->i_lock);