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| author | Jan Kara <jack@suse.cz> | 2009-03-27 17:20:40 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2009-03-27 17:20:40 -0400 |
| commit | 86db97c87f744364d5889ca8a4134ca2048b8f83 (patch) | |
| tree | 420c3c60be2c1a7e644fe4082226d79f31d8b911 | |
| parent | cc0fb9ad7dbc5a149f4957a0dd6d65881d3d385b (diff) | |
| download | linux-86db97c87f744364d5889ca8a4134ca2048b8f83.tar.bz2 | |
jbd2: Update locking coments
Update information about locking in JBD2 revoke code. Inconsistency in
comments found by Lin Tan <tammy000@gmail.com>.
CC: Lin Tan <tammy000@gmail.com>.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
| -rw-r--r-- | fs/jbd2/revoke.c | 24 |
1 files changed, 19 insertions, 5 deletions
diff --git a/fs/jbd2/revoke.c b/fs/jbd2/revoke.c index 257ff2625765..bbe6d592d8b3 100644 --- a/fs/jbd2/revoke.c +++ b/fs/jbd2/revoke.c @@ -55,6 +55,25 @@ * need do nothing. * RevokeValid set, Revoked set: * buffer has been revoked. + * + * Locking rules: + * We keep two hash tables of revoke records. One hashtable belongs to the + * running transaction (is pointed to by journal->j_revoke), the other one + * belongs to the committing transaction. Accesses to the second hash table + * happen only from the kjournald and no other thread touches this table. Also + * journal_switch_revoke_table() which switches which hashtable belongs to the + * running and which to the committing transaction is called only from + * kjournald. Therefore we need no locks when accessing the hashtable belonging + * to the committing transaction. + * + * All users operating on the hash table belonging to the running transaction + * have a handle to the transaction. Therefore they are safe from kjournald + * switching hash tables under them. For operations on the lists of entries in + * the hash table j_revoke_lock is used. + * + * Finally, also replay code uses the hash tables but at this moment noone else + * can touch them (filesystem isn't mounted yet) and hence no locking is + * needed. */ #ifndef __KERNEL__ @@ -401,8 +420,6 @@ int jbd2_journal_revoke(handle_t *handle, unsigned long long blocknr, * the second time we would still have a pending revoke to cancel. So, * do not trust the Revoked bit on buffers unless RevokeValid is also * set. - * - * The caller must have the journal locked. */ int jbd2_journal_cancel_revoke(handle_t *handle, struct journal_head *jh) { @@ -480,10 +497,7 @@ void jbd2_journal_switch_revoke_table(journal_t *journal) /* * Write revoke records to the journal for all entries in the current * revoke hash, deleting the entries as we go. - * - * Called with the journal lock held. */ - void jbd2_journal_write_revoke_records(journal_t *journal, transaction_t *transaction) { |