From b8a6176c214cf9aa2679131ed7e4515cddaadc33 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Wed, 1 Nov 2017 16:36:45 +0100 Subject: ext4: Support for synchronous DAX faults We return IOMAP_F_DIRTY flag from ext4_iomap_begin() when asked to prepare blocks for writing and the inode has some uncommitted metadata changes. In the fault handler ext4_dax_fault() we then detect this case (through VM_FAULT_NEEDDSYNC return value) and call helper dax_finish_sync_fault() to flush metadata changes and insert page table entry. 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. Reviewed-by: Ross Zwisler Signed-off-by: Jan Kara Signed-off-by: Dan Williams --- fs/ext4/file.c | 15 ++++++++++++++- fs/ext4/inode.c | 15 +++++++++++++++ fs/jbd2/journal.c | 17 +++++++++++++++++ 3 files changed, 46 insertions(+), 1 deletion(-) (limited to 'fs') diff --git a/fs/ext4/file.c b/fs/ext4/file.c index 208adfc3e673..08a1d1a33a90 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -26,6 +26,7 @@ #include #include #include +#include #include "ext4.h" #include "ext4_jbd2.h" #include "xattr.h" @@ -295,6 +296,7 @@ static int ext4_dax_huge_fault(struct vm_fault *vmf, */ bool write = (vmf->flags & FAULT_FLAG_WRITE) && (vmf->vma->vm_flags & VM_SHARED); + pfn_t pfn; if (write) { sb_start_pagefault(sb); @@ -310,9 +312,12 @@ static int ext4_dax_huge_fault(struct vm_fault *vmf, } else { down_read(&EXT4_I(inode)->i_mmap_sem); } - result = dax_iomap_fault(vmf, pe_size, NULL, &ext4_iomap_ops); + result = dax_iomap_fault(vmf, pe_size, &pfn, &ext4_iomap_ops); if (write) { ext4_journal_stop(handle); + /* Handling synchronous page fault? */ + if (result & VM_FAULT_NEEDDSYNC) + result = dax_finish_sync_fault(vmf, pe_size, pfn); up_read(&EXT4_I(inode)->i_mmap_sem); sb_end_pagefault(sb); } else { @@ -350,6 +355,13 @@ static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma) if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb)))) return -EIO; + /* + * We don't support synchronous mappings for non-DAX files. At least + * until someone comes with a sensible use case. + */ + if (!IS_DAX(file_inode(file)) && (vma->vm_flags & VM_SYNC)) + return -EOPNOTSUPP; + file_accessed(file); if (IS_DAX(file_inode(file))) { vma->vm_ops = &ext4_dax_vm_ops; @@ -719,6 +731,7 @@ const struct file_operations ext4_file_operations = { .compat_ioctl = ext4_compat_ioctl, #endif .mmap = ext4_file_mmap, + .mmap_supported_flags = MAP_SYNC, .open = ext4_file_open, .release = ext4_release_file, .fsync = ext4_sync_file, diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 31db875bc7a1..13a198924a0f 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3394,6 +3394,19 @@ static int ext4_releasepage(struct page *page, gfp_t wait) } #ifdef CONFIG_FS_DAX +static bool ext4_inode_datasync_dirty(struct inode *inode) +{ + journal_t *journal = EXT4_SB(inode->i_sb)->s_journal; + + if (journal) + return !jbd2_transaction_committed(journal, + EXT4_I(inode)->i_datasync_tid); + /* Any metadata buffers to write? */ + if (!list_empty(&inode->i_mapping->private_list)) + return true; + return inode->i_state & I_DIRTY_DATASYNC; +} + static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length, unsigned flags, struct iomap *iomap) { @@ -3466,6 +3479,8 @@ retry: } iomap->flags = 0; + if ((flags & IOMAP_WRITE) && ext4_inode_datasync_dirty(inode)) + iomap->flags |= IOMAP_F_DIRTY; iomap->bdev = inode->i_sb->s_bdev; iomap->dax_dev = sbi->s_daxdev; iomap->offset = first_block << blkbits; diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c index 7d5ef3bf3f3e..fa8cde498b4b 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -738,6 +738,23 @@ 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; +} +EXPORT_SYMBOL(jbd2_transaction_committed); + /* * When this function returns the transaction corresponding to tid * will be completed. If the transaction has currently running, start -- cgit v1.2.3