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![Theodore Ts'o](/assets/img/avatar_default.png)
So we can better understand what bits of ext4 are responsible for long-running jbd2 handles, use jbd2__journal_start() so we can pass context information for logging purposes. The recommended way for finding the longer-running handles is: T=/sys/kernel/debug/tracing EVENT=$T/events/jbd2/jbd2_handle_stats echo "interval > 5" > $EVENT/filter echo 1 > $EVENT/enable ./run-my-fs-benchmark cat $T/trace > /tmp/problem-handles This will list handles that were active for longer than 20ms. Having longer-running handles is bad, because a commit started at the wrong time could stall for those 20+ milliseconds, which could delay an fsync() or an O_SYNC operation. Here is an example line from the trace file describing a handle which lived on for 311 jiffies, or over 1.2 seconds: postmark-2917 [000] .... 196.435786: jbd2_handle_stats: dev 254,32 tid 570 type 2 line_no 2541 interval 311 sync 0 requested_blocks 1 dirtied_blocks 0 Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
257 lines
6.2 KiB
C
257 lines
6.2 KiB
C
/*
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* Interface between ext4 and JBD
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*/
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#include "ext4_jbd2.h"
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#include <trace/events/ext4.h>
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/* Just increment the non-pointer handle value */
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static handle_t *ext4_get_nojournal(void)
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{
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handle_t *handle = current->journal_info;
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unsigned long ref_cnt = (unsigned long)handle;
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BUG_ON(ref_cnt >= EXT4_NOJOURNAL_MAX_REF_COUNT);
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ref_cnt++;
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handle = (handle_t *)ref_cnt;
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current->journal_info = handle;
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return handle;
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}
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/* Decrement the non-pointer handle value */
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static void ext4_put_nojournal(handle_t *handle)
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{
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unsigned long ref_cnt = (unsigned long)handle;
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BUG_ON(ref_cnt == 0);
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ref_cnt--;
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handle = (handle_t *)ref_cnt;
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current->journal_info = handle;
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}
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/*
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* Wrappers for jbd2_journal_start/end.
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*/
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handle_t *__ext4_journal_start_sb(struct super_block *sb, unsigned int line,
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int type, int nblocks)
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{
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journal_t *journal;
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trace_ext4_journal_start(sb, nblocks, _RET_IP_);
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if (sb->s_flags & MS_RDONLY)
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return ERR_PTR(-EROFS);
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WARN_ON(sb->s_writers.frozen == SB_FREEZE_COMPLETE);
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journal = EXT4_SB(sb)->s_journal;
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if (!journal)
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return ext4_get_nojournal();
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/*
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* Special case here: if the journal has aborted behind our
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* backs (eg. EIO in the commit thread), then we still need to
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* take the FS itself readonly cleanly.
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*/
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if (is_journal_aborted(journal)) {
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ext4_abort(sb, "Detected aborted journal");
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return ERR_PTR(-EROFS);
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}
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return jbd2__journal_start(journal, nblocks, GFP_NOFS, type, line);
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}
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int __ext4_journal_stop(const char *where, unsigned int line, handle_t *handle)
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{
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struct super_block *sb;
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int err;
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int rc;
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if (!ext4_handle_valid(handle)) {
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ext4_put_nojournal(handle);
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return 0;
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}
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sb = handle->h_transaction->t_journal->j_private;
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err = handle->h_err;
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rc = jbd2_journal_stop(handle);
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if (!err)
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err = rc;
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if (err)
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__ext4_std_error(sb, where, line, err);
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return err;
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}
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void ext4_journal_abort_handle(const char *caller, unsigned int line,
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const char *err_fn, struct buffer_head *bh,
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handle_t *handle, int err)
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{
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char nbuf[16];
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const char *errstr = ext4_decode_error(NULL, err, nbuf);
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BUG_ON(!ext4_handle_valid(handle));
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if (bh)
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BUFFER_TRACE(bh, "abort");
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if (!handle->h_err)
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handle->h_err = err;
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if (is_handle_aborted(handle))
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return;
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printk(KERN_ERR "EXT4-fs: %s:%d: aborting transaction: %s in %s\n",
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caller, line, errstr, err_fn);
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jbd2_journal_abort_handle(handle);
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}
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int __ext4_journal_get_write_access(const char *where, unsigned int line,
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handle_t *handle, struct buffer_head *bh)
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{
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int err = 0;
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if (ext4_handle_valid(handle)) {
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err = jbd2_journal_get_write_access(handle, bh);
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if (err)
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ext4_journal_abort_handle(where, line, __func__, bh,
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handle, err);
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}
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return err;
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}
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/*
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* The ext4 forget function must perform a revoke if we are freeing data
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* which has been journaled. Metadata (eg. indirect blocks) must be
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* revoked in all cases.
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*
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* "bh" may be NULL: a metadata block may have been freed from memory
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* but there may still be a record of it in the journal, and that record
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* still needs to be revoked.
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*
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* If the handle isn't valid we're not journaling, but we still need to
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* call into ext4_journal_revoke() to put the buffer head.
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*/
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int __ext4_forget(const char *where, unsigned int line, handle_t *handle,
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int is_metadata, struct inode *inode,
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struct buffer_head *bh, ext4_fsblk_t blocknr)
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{
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int err;
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might_sleep();
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trace_ext4_forget(inode, is_metadata, blocknr);
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BUFFER_TRACE(bh, "enter");
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jbd_debug(4, "forgetting bh %p: is_metadata = %d, mode %o, "
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"data mode %x\n",
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bh, is_metadata, inode->i_mode,
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test_opt(inode->i_sb, DATA_FLAGS));
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/* In the no journal case, we can just do a bforget and return */
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if (!ext4_handle_valid(handle)) {
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bforget(bh);
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return 0;
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}
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/* Never use the revoke function if we are doing full data
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* journaling: there is no need to, and a V1 superblock won't
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* support it. Otherwise, only skip the revoke on un-journaled
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* data blocks. */
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if (test_opt(inode->i_sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA ||
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(!is_metadata && !ext4_should_journal_data(inode))) {
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if (bh) {
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BUFFER_TRACE(bh, "call jbd2_journal_forget");
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err = jbd2_journal_forget(handle, bh);
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if (err)
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ext4_journal_abort_handle(where, line, __func__,
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bh, handle, err);
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return err;
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}
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return 0;
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}
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/*
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* data!=journal && (is_metadata || should_journal_data(inode))
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*/
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BUFFER_TRACE(bh, "call jbd2_journal_revoke");
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err = jbd2_journal_revoke(handle, blocknr, bh);
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if (err) {
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ext4_journal_abort_handle(where, line, __func__,
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bh, handle, err);
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__ext4_abort(inode->i_sb, where, line,
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"error %d when attempting revoke", err);
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}
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BUFFER_TRACE(bh, "exit");
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return err;
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}
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int __ext4_journal_get_create_access(const char *where, unsigned int line,
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handle_t *handle, struct buffer_head *bh)
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{
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int err = 0;
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if (ext4_handle_valid(handle)) {
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err = jbd2_journal_get_create_access(handle, bh);
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if (err)
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ext4_journal_abort_handle(where, line, __func__,
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bh, handle, err);
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}
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return err;
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}
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int __ext4_handle_dirty_metadata(const char *where, unsigned int line,
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handle_t *handle, struct inode *inode,
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struct buffer_head *bh)
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{
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int err = 0;
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if (ext4_handle_valid(handle)) {
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err = jbd2_journal_dirty_metadata(handle, bh);
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if (err) {
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/* Errors can only happen if there is a bug */
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handle->h_err = err;
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__ext4_journal_stop(where, line, handle);
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}
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} else {
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if (inode)
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mark_buffer_dirty_inode(bh, inode);
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else
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mark_buffer_dirty(bh);
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if (inode && inode_needs_sync(inode)) {
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sync_dirty_buffer(bh);
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if (buffer_req(bh) && !buffer_uptodate(bh)) {
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struct ext4_super_block *es;
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es = EXT4_SB(inode->i_sb)->s_es;
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es->s_last_error_block =
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cpu_to_le64(bh->b_blocknr);
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ext4_error_inode(inode, where, line,
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bh->b_blocknr,
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"IO error syncing itable block");
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err = -EIO;
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}
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}
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}
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return err;
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}
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int __ext4_handle_dirty_super(const char *where, unsigned int line,
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handle_t *handle, struct super_block *sb)
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{
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struct buffer_head *bh = EXT4_SB(sb)->s_sbh;
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int err = 0;
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ext4_superblock_csum_set(sb);
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if (ext4_handle_valid(handle)) {
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err = jbd2_journal_dirty_metadata(handle, bh);
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if (err)
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ext4_journal_abort_handle(where, line, __func__,
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bh, handle, err);
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} else
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mark_buffer_dirty(bh);
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return err;
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}
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