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xfs: make the log ticket transaction id random 

The transaction ID that is written to the log for a transaction is
currently set by taking the lower 32 bits of the memory address of
the ticket structure.  This is not guaranteed to be unique as
tickets comes from a slab and slots can be reallocated immediately
after being freed. As a result, there is no guarantee of uniqueness
in the ticket ID value.

Fix this by assigning a random number to the ticket ID field so that
it is extremely unlikely that duplicates will occur and remove the
possibility of transactions being mixed up during recovery due to
duplicate IDs.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Dave Chinner 2010-04-14 15:47:55 +10:00 committed by Alex Elder
parent 36adecff50
commit f983710758
1 changed files with 1 additions and 1 deletions
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2
fs/xfs/xfs_log.c
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@ -3417,7 +3417,7 @@ xlog_ticket_alloc(
tic->t_curr_res = unit_bytes;
tic->t_cnt = cnt;
tic->t_ocnt = cnt;
tic->t_tid = (xlog_tid_t)((__psint_t)tic & 0xffffffff);
tic->t_tid = random32();
tic->t_clientid = client;
tic->t_flags = XLOG_TIC_INITED;
tic->t_trans_type = 0;