We return IOMAP_F_NEEDDSYNC flag from ext4_iomap_begin() for a synchronous write fault when inode has some uncommitted metadata changes. In the fault handler ext4_dax_fault() we then detect this case, call vfs_fsync_range() to make sure all metadata is committed, and call dax_pfn_mkwrite() to mark PTE as writeable. Note that this will also dirty corresponding radix tree entry which is what we want - fsync(2) will still provide data integrity guarantees for applications not using userspace flushing. And applications using userspace flushing can avoid calling fsync(2) and thus avoid the performance overhead.
Signed-off-by: Jan Kara <[email protected]> --- fs/ext4/file.c | 35 +++++++++++++++++++++++++++++------ fs/ext4/inode.c | 4 ++++ fs/jbd2/journal.c | 16 ++++++++++++++++ include/linux/jbd2.h | 1 + 4 files changed, 50 insertions(+), 6 deletions(-) diff --git a/fs/ext4/file.c b/fs/ext4/file.c index d401403e5095..b221d0b546b0 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -287,16 +287,39 @@ static int ext4_dax_huge_fault(struct vm_fault *vmf, down_read(&EXT4_I(inode)->i_mmap_sem); handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE, EXT4_DATA_TRANS_BLOCKS(sb)); + if (IS_ERR(handle)) { + up_read(&EXT4_I(inode)->i_mmap_sem); + sb_end_pagefault(sb); + return VM_FAULT_SIGBUS; + } } else { down_read(&EXT4_I(inode)->i_mmap_sem); } - if (!IS_ERR(handle)) - result = dax_iomap_fault(vmf, pe_size, false, &ext4_iomap_ops); - else - result = VM_FAULT_SIGBUS; + result = dax_iomap_fault(vmf, pe_size, IS_SYNC(inode), &ext4_iomap_ops); if (write) { - if (!IS_ERR(handle)) - ext4_journal_stop(handle); + ext4_journal_stop(handle); + /* Write fault but PFN mapped only RO? */ + if (result & VM_FAULT_RO) { + int err; + loff_t start = ((loff_t)vmf->pgoff) << PAGE_SHIFT; + size_t len = 0; + + if (pe_size == PE_SIZE_PTE) + len = PAGE_SIZE; +#ifdef CONFIG_FS_DAX_PMD + else if (pe_size == PE_SIZE_PMD) + len = HPAGE_PMD_SIZE; + else + WARN_ON_ONCE(1); +#endif + WARN_ON_ONCE(!IS_SYNC(inode)); + err = vfs_fsync_range(vmf->vma->vm_file, start, + start + len - 1, 1); + if (err) + result = VM_FAULT_SIGBUS; + else + result = dax_pfn_mkwrite(vmf, pe_size); + } up_read(&EXT4_I(inode)->i_mmap_sem); sb_end_pagefault(sb); } else { diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 3c600f02673f..e68231bb227c 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3429,6 +3429,10 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length, } iomap->flags = 0; + if ((flags & IOMAP_FAULT) && (flags & IOMAP_WRITE) && IS_SYNC(inode) && + !jbd2_transaction_committed(EXT4_SB(inode->i_sb)->s_journal, + EXT4_I(inode)->i_datasync_tid)) + iomap->flags |= IOMAP_F_NEEDDSYNC; bdev = inode->i_sb->s_bdev; iomap->bdev = bdev; if (blk_queue_dax(bdev->bd_queue)) diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c index 7d5ef3bf3f3e..e0f436c42d67 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -738,6 +738,22 @@ int jbd2_log_wait_commit(journal_t *journal, tid_t tid) return err; } +/* Return 1 when transaction with given tid has already committed. */ +int jbd2_transaction_committed(journal_t *journal, tid_t tid) +{ + int ret = 1; + + read_lock(&journal->j_state_lock); + if (journal->j_running_transaction && + journal->j_running_transaction->t_tid == tid) + ret = 0; + if (journal->j_committing_transaction && + journal->j_committing_transaction->t_tid == tid) + ret = 0; + read_unlock(&journal->j_state_lock); + return ret; +} + /* * When this function returns the transaction corresponding to tid * will be completed. If the transaction has currently running, start diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h index 606b6bce3a5b..296d1e0ea87b 100644 --- a/include/linux/jbd2.h +++ b/include/linux/jbd2.h @@ -1367,6 +1367,7 @@ int jbd2_log_start_commit(journal_t *journal, tid_t tid); int __jbd2_log_start_commit(journal_t *journal, tid_t tid); int jbd2_journal_start_commit(journal_t *journal, tid_t *tid); int jbd2_log_wait_commit(journal_t *journal, tid_t tid); +int jbd2_transaction_committed(journal_t *journal, tid_t tid); int jbd2_complete_transaction(journal_t *journal, tid_t tid); int jbd2_log_do_checkpoint(journal_t *journal); int jbd2_trans_will_send_data_barrier(journal_t *journal, tid_t tid); -- 2.12.3 _______________________________________________ Linux-nvdimm mailing list [email protected] https://lists.01.org/mailman/listinfo/linux-nvdimm
