On 08/18/2014 01:31 PM, Ivan Shapovalov wrote:
When discard was enabled, immediate deallocations were made deferred in order
to record these extents in the atom's delete set and, consequently, allow
their discarding.
However, this is wrong in the following way. Immediate deallocations make use
of target allocation stage and ancillary flags like BA_PERMANENT and BA_FORMATTED.
By converting immediate deallocations to deferred, these flags are essentially
dropped, and application of deferred deallocations in reiser4_post_write_back_hook()
uses an equivalent of BLOCK_NOT_COUNTED stage and BA_FORMATTED flag.
Dropping this hack does not hinder efficiency of the discard procedure, because
immediate deallocations are now used only to deallocate "just allocated" and not
yet written blocks, which actually do not need to be discarded.
The idea to defer every "successful" deallocation regardless of discard
support status looks OK, but I don't like the first patch (1/2), so
let's try
to improve it..
So, we want to defer also deallocations in the following 2 places:
1) in dealloc_tx_list();
2) in dealloc_wmap_actor().
Here we should take care about block stages.
Let's take a look where and how they were allocated. There are exactly
2 places:
a) in get_more_wandered_blocks() with block_stage = BLOCK_GRABBED;
b) in alloc_tx() with block_stage = BLOCK_GRABBED.
Note, that alloc_blocks() with the stage BLOCK_GRABBED calls
grabbed2used(). This is exactly what we want in apply_dset() called by
post_write_back_hook.
That is, just adding BA_DEFER to (1) and (2) with the patch 2/2 should work.
Please, make sure..
P.S. In (1)-(2) we allocate with stage BLOCK_GRABBED, but in (a)-(b) we
deallocate with stage BLOCK_NOT_COUNTED. It can confuse. Let's allocate
with stage BLOCK_NOT_COUNTED: from the standpoint of alloc_blocks() it
doesn't matter.
Thanks.
Signed-off-by: Ivan Shapovalov <intelfx100@xxxxxxxxx>
---
fs/reiser4/block_alloc.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/fs/reiser4/block_alloc.c b/fs/reiser4/block_alloc.c
index 324b11c..33ca86c 100644
--- a/fs/reiser4/block_alloc.c
+++ b/fs/reiser4/block_alloc.c
@@ -1008,8 +1008,7 @@ reiser4_dealloc_blocks(const reiser4_block_nr * start,
spin_unlock_reiser4_super(sbinfo);
}
- if ((flags & BA_DEFER) ||
- reiser4_is_set(reiser4_get_current_sb(), REISER4_DISCARD)) {
+ if (flags & BA_DEFER) {
/* store deleted block numbers in the atom's deferred delete set
for further actual deletion */
do {
--
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