lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Message-Id: <1365456754-29373-8-git-send-email-jack@suse.cz> Date: Mon, 8 Apr 2013 23:32:12 +0200 From: Jan Kara <jack@...e.cz> To: Ted Tso <tytso@....edu> Cc: linux-ext4@...r.kernel.org, Jan Kara <jack@...e.cz> Subject: [PATCH 07/29] jbd2: Refine waiting for shadow buffers Currently when we add a buffer to a transaction, we wait until the buffer is removed from BJ_Shadow list (so that we prevent any changes to the buffer that is just written to the journal). This can take unnecessarily long as a lot happens between the time the buffer is submitted to the journal and the time when we remove the buffer from BJ_Shadow list (e.g. we wait for all data buffers in the transaction, we issue a cache flush etc.). Also this creates a dependency of do_get_write_access() on transaction commit (namely waiting for data IO to complete) which we want to avoid when implementing transaction reservation. So we modify commit code to set new BH_Shadow flag when temporary shadowing buffer is created and we clear that flag once IO on that buffer is complete. This allows do_get_write_access() to wait only for BH_Shadow bit and thus removes the dependency on data IO completion. Signed-off-by: Jan Kara <jack@...e.cz> --- fs/jbd2/commit.c | 20 ++++++++++---------- fs/jbd2/journal.c | 2 ++ fs/jbd2/transaction.c | 44 +++++++++++++++++++------------------------- include/linux/jbd.h | 25 +++++++++++++++++++++++++ include/linux/jbd2.h | 28 ++++++++++++++++++++++++++++ include/linux/jbd_common.h | 26 -------------------------- 6 files changed, 84 insertions(+), 61 deletions(-) diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c index 1a03762..4863f5b 100644 --- a/fs/jbd2/commit.c +++ b/fs/jbd2/commit.c @@ -30,15 +30,22 @@ #include <trace/events/jbd2.h> /* - * Default IO end handler for temporary BJ_IO buffer_heads. + * IO end handler for temporary buffer_heads handling writes to the journal. */ static void journal_end_buffer_io_sync(struct buffer_head *bh, int uptodate) { + struct buffer_head *orig_bh = bh->b_private; + BUFFER_TRACE(bh, ""); if (uptodate) set_buffer_uptodate(bh); else clear_buffer_uptodate(bh); + if (orig_bh) { + clear_bit_unlock(BH_Shadow, &orig_bh->b_state); + smp_mb__after_clear_bit(); + wake_up_bit(&orig_bh->b_state, BH_Shadow); + } unlock_buffer(bh); } @@ -818,7 +825,7 @@ start_journal_io: jbd2_unfile_log_bh(bh); /* - * The list contains temporary buffer heads created by + * The list contains temporary buffer heas created by * jbd2_journal_write_metadata_buffer(). */ BUFFER_TRACE(bh, "dumping temporary bh"); @@ -831,6 +838,7 @@ start_journal_io: bh = jh2bh(jh); clear_buffer_jwrite(bh); J_ASSERT_BH(bh, buffer_jbddirty(bh)); + J_ASSERT_BH(bh, !buffer_shadow(bh)); /* The metadata is now released for reuse, but we need to remember it against this transaction so that when @@ -838,14 +846,6 @@ start_journal_io: required. */ JBUFFER_TRACE(jh, "file as BJ_Forget"); jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget); - /* - * Wake up any transactions which were waiting for this IO to - * complete. The barrier must be here so that changes by - * jbd2_journal_file_buffer() take effect before wake_up_bit() - * does the waitqueue check. - */ - smp_mb(); - wake_up_bit(&bh->b_state, BH_Unshadow); JBUFFER_TRACE(jh, "brelse shadowed buffer"); __brelse(bh); } diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c index e03aae0..e9a9cdb 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -453,6 +453,7 @@ repeat: new_bh->b_size = bh_in->b_size; new_bh->b_bdev = journal->j_dev; new_bh->b_blocknr = blocknr; + new_bh->b_private = bh_in; set_buffer_mapped(new_bh); set_buffer_dirty(new_bh); @@ -467,6 +468,7 @@ repeat: spin_lock(&journal->j_list_lock); __jbd2_journal_file_buffer(jh_in, transaction, BJ_Shadow); spin_unlock(&journal->j_list_lock); + set_buffer_shadow(bh_in); jbd_unlock_bh_state(bh_in); return do_escape | (done_copy_out << 1); diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c index bc35899..81df09c 100644 --- a/fs/jbd2/transaction.c +++ b/fs/jbd2/transaction.c @@ -620,6 +620,12 @@ static void warn_dirty_buffer(struct buffer_head *bh) bdevname(bh->b_bdev, b), (unsigned long long)bh->b_blocknr); } +static int sleep_on_shadow_bh(void *word) +{ + io_schedule(); + return 0; +} + /* * If the buffer is already part of the current transaction, then there * is nothing we need to do. If it is already part of a prior @@ -747,41 +753,29 @@ repeat: * journaled. If the primary copy is already going to * disk then we cannot do copy-out here. */ - if (jh->b_jlist == BJ_Shadow) { - DEFINE_WAIT_BIT(wait, &bh->b_state, BH_Unshadow); - wait_queue_head_t *wqh; - - wqh = bit_waitqueue(&bh->b_state, BH_Unshadow); - + if (buffer_shadow(bh)) { JBUFFER_TRACE(jh, "on shadow: sleep"); jbd_unlock_bh_state(bh); - /* commit wakes up all shadow buffers after IO */ - for ( ; ; ) { - prepare_to_wait(wqh, &wait.wait, - TASK_UNINTERRUPTIBLE); - if (jh->b_jlist != BJ_Shadow) - break; - schedule(); - } - finish_wait(wqh, &wait.wait); + wait_on_bit(&bh->b_state, BH_Shadow, + sleep_on_shadow_bh, TASK_UNINTERRUPTIBLE); goto repeat; } - /* Only do the copy if the currently-owning transaction - * still needs it. If it is on the Forget list, the - * committing transaction is past that stage. The - * buffer had better remain locked during the kmalloc, - * but that should be true --- we hold the journal lock - * still and the buffer is already on the BUF_JOURNAL - * list so won't be flushed. + /* + * Only do the copy if the currently-owning transaction still + * needs it. If buffer isn't on BJ_Metadata list, the + * committing transaction is past that stage (here we use the + * fact that BH_Shadow is set under bh_state lock together with + * refiling to BJ_Shadow list and at this point we know the + * buffer doesn't have BH_Shadow set). * * Subtle point, though: if this is a get_undo_access, * then we will be relying on the frozen_data to contain * the new value of the committed_data record after the * transaction, so we HAVE to force the frozen_data copy - * in that case. */ - - if (jh->b_jlist != BJ_Forget || force_copy) { + * in that case. + */ + if (jh->b_jlist == BJ_Metadata || force_copy) { JBUFFER_TRACE(jh, "generate frozen data"); if (!frozen_buffer) { JBUFFER_TRACE(jh, "allocate memory for buffer"); diff --git a/include/linux/jbd.h b/include/linux/jbd.h index c8f3297..1c36b0c 100644 --- a/include/linux/jbd.h +++ b/include/linux/jbd.h @@ -244,6 +244,31 @@ typedef struct journal_superblock_s #include <linux/fs.h> #include <linux/sched.h> + +enum jbd_state_bits { + BH_JBD /* Has an attached ext3 journal_head */ + = BH_PrivateStart, + BH_JWrite, /* Being written to log (@@@ DEBUGGING) */ + BH_Freed, /* Has been freed (truncated) */ + BH_Revoked, /* Has been revoked from the log */ + BH_RevokeValid, /* Revoked flag is valid */ + BH_JBDDirty, /* Is dirty but journaled */ + BH_State, /* Pins most journal_head state */ + BH_JournalHead, /* Pins bh->b_private and jh->b_bh */ + BH_Unshadow, /* Dummy bit, for BJ_Shadow wakeup filtering */ + BH_JBDPrivateStart, /* First bit available for private use by FS */ +}; + +BUFFER_FNS(JBD, jbd) +BUFFER_FNS(JWrite, jwrite) +BUFFER_FNS(JBDDirty, jbddirty) +TAS_BUFFER_FNS(JBDDirty, jbddirty) +BUFFER_FNS(Revoked, revoked) +TAS_BUFFER_FNS(Revoked, revoked) +BUFFER_FNS(RevokeValid, revokevalid) +TAS_BUFFER_FNS(RevokeValid, revokevalid) +BUFFER_FNS(Freed, freed) + #include <linux/jbd_common.h> #define J_ASSERT(assert) BUG_ON(!(assert)) diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h index 4584518..be5115f 100644 --- a/include/linux/jbd2.h +++ b/include/linux/jbd2.h @@ -302,6 +302,34 @@ typedef struct journal_superblock_s #include <linux/fs.h> #include <linux/sched.h> + +enum jbd_state_bits { + BH_JBD /* Has an attached ext3 journal_head */ + = BH_PrivateStart, + BH_JWrite, /* Being written to log (@@@ DEBUGGING) */ + BH_Freed, /* Has been freed (truncated) */ + BH_Revoked, /* Has been revoked from the log */ + BH_RevokeValid, /* Revoked flag is valid */ + BH_JBDDirty, /* Is dirty but journaled */ + BH_State, /* Pins most journal_head state */ + BH_JournalHead, /* Pins bh->b_private and jh->b_bh */ + BH_Shadow, /* IO on shadow buffer is running */ + BH_Verified, /* Metadata block has been verified ok */ + BH_JBDPrivateStart, /* First bit available for private use by FS */ +}; + +BUFFER_FNS(JBD, jbd) +BUFFER_FNS(JWrite, jwrite) +BUFFER_FNS(JBDDirty, jbddirty) +TAS_BUFFER_FNS(JBDDirty, jbddirty) +BUFFER_FNS(Revoked, revoked) +TAS_BUFFER_FNS(Revoked, revoked) +BUFFER_FNS(RevokeValid, revokevalid) +TAS_BUFFER_FNS(RevokeValid, revokevalid) +BUFFER_FNS(Freed, freed) +BUFFER_FNS(Shadow, shadow) +BUFFER_FNS(Verified, verified) + #include <linux/jbd_common.h> #define J_ASSERT(assert) BUG_ON(!(assert)) diff --git a/include/linux/jbd_common.h b/include/linux/jbd_common.h index 6133679..b1f7089 100644 --- a/include/linux/jbd_common.h +++ b/include/linux/jbd_common.h @@ -1,32 +1,6 @@ #ifndef _LINUX_JBD_STATE_H #define _LINUX_JBD_STATE_H -enum jbd_state_bits { - BH_JBD /* Has an attached ext3 journal_head */ - = BH_PrivateStart, - BH_JWrite, /* Being written to log (@@@ DEBUGGING) */ - BH_Freed, /* Has been freed (truncated) */ - BH_Revoked, /* Has been revoked from the log */ - BH_RevokeValid, /* Revoked flag is valid */ - BH_JBDDirty, /* Is dirty but journaled */ - BH_State, /* Pins most journal_head state */ - BH_JournalHead, /* Pins bh->b_private and jh->b_bh */ - BH_Unshadow, /* Dummy bit, for BJ_Shadow wakeup filtering */ - BH_Verified, /* Metadata block has been verified ok */ - BH_JBDPrivateStart, /* First bit available for private use by FS */ -}; - -BUFFER_FNS(JBD, jbd) -BUFFER_FNS(JWrite, jwrite) -BUFFER_FNS(JBDDirty, jbddirty) -TAS_BUFFER_FNS(JBDDirty, jbddirty) -BUFFER_FNS(Revoked, revoked) -TAS_BUFFER_FNS(Revoked, revoked) -BUFFER_FNS(RevokeValid, revokevalid) -TAS_BUFFER_FNS(RevokeValid, revokevalid) -BUFFER_FNS(Freed, freed) -BUFFER_FNS(Verified, verified) - static inline struct buffer_head *jh2bh(struct journal_head *jh) { return jh->b_bh; -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Powered by blists - more mailing lists