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| author | Jan Kara <jack@suse.cz> | 2009-04-13 23:40:06 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-04-14 00:04:32 +0200 |
| commit | 32433879480d13bc019d5a067ce884064a93dd63 (patch) | |
| tree | 652230bb84c0d93d06b8ed17049e9a8229283907 | |
| parent | mm: document get_user_pages_fast() (diff) | |
| download | linux-32433879480d13bc019d5a067ce884064a93dd63.tar.xz linux-32433879480d13bc019d5a067ce884064a93dd63.zip | |
jbd: update locking coments
Update information about locking in JBD revoke code.
Reported-by: Lin Tan <tammy000@gmail.com>.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | fs/jbd/revoke.c | 24 |
1 files changed, 19 insertions, 5 deletions
diff --git a/fs/jbd/revoke.c b/fs/jbd/revoke.c index c7bd649bbbdc..3e9afc2a91d2 100644 --- a/fs/jbd/revoke.c +++ b/fs/jbd/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 * RevokeValid set, Revoked set: * buffer has been revoked.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__ @@ -402,8 +421,6 @@ int journal_revoke(handle_t *handle, unsigned 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 journal_cancel_revoke(handle_t *handle, struct journal_head *jh) { @@ -481,10 +498,7 @@ void 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 journal_write_revoke_records(journal_t *journal, transaction_t *transaction) { |