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Commit 86db97c8 authored by Jan Kara's avatar Jan Kara Committed by Theodore Ts'o
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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: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent cc0fb9ad

fs/jbd2/revoke.c

+19 −5
Original line number Diff line number Diff line
@@ -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 *			buffer has been revoked.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)

{