From caa51d26f85c248f1c4f43a870ad3ef84bf9eb8f Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Wed, 1 Nov 2017 16:36:42 +0100 Subject: dax, iomap: Add support for synchronous faults Add a flag to iomap interface informing the caller that inode needs fdstasync(2) for returned extent to become persistent and use it in DAX fault code so that we don't map such extents into page tables immediately. Instead we propagate the information that fdatasync(2) is necessary from dax_iomap_fault() with a new VM_FAULT_NEEDDSYNC flag. Filesystem fault handler is then responsible for calling fdatasync(2) and inserting pfn into page tables. Reviewed-by: Ross Zwisler Reviewed-by: Christoph Hellwig Signed-off-by: Jan Kara Signed-off-by: Dan Williams --- fs/dax.c | 39 +++++++++++++++++++++++++++++++++++++-- 1 file changed, 37 insertions(+), 2 deletions(-) (limited to 'fs/dax.c') diff --git a/fs/dax.c b/fs/dax.c index efc210ff6665..bb9ff907738c 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -1091,6 +1091,7 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp, unsigned flags = IOMAP_FAULT; int error, major = 0; bool write = vmf->flags & FAULT_FLAG_WRITE; + bool sync; int vmf_ret = 0; void *entry; pfn_t pfn; @@ -1169,6 +1170,8 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp, goto finish_iomap; } + sync = (vma->vm_flags & VM_SYNC) && (iomap.flags & IOMAP_F_DIRTY); + switch (iomap.type) { case IOMAP_MAPPED: if (iomap.flags & IOMAP_F_NEW) { @@ -1182,12 +1185,27 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp, entry = dax_insert_mapping_entry(mapping, vmf, entry, dax_iomap_sector(&iomap, pos), - 0, write); + 0, write && !sync); if (IS_ERR(entry)) { error = PTR_ERR(entry); goto error_finish_iomap; } + /* + * If we are doing synchronous page fault and inode needs fsync, + * we can insert PTE into page tables only after that happens. + * Skip insertion for now and return the pfn so that caller can + * insert it after fsync is done. + */ + if (sync) { + if (WARN_ON_ONCE(!pfnp)) { + error = -EIO; + goto error_finish_iomap; + } + *pfnp = pfn; + vmf_ret = VM_FAULT_NEEDDSYNC | major; + goto finish_iomap; + } trace_dax_insert_mapping(inode, vmf, entry); if (write) error = vm_insert_mixed_mkwrite(vma, vaddr, pfn); @@ -1287,6 +1305,7 @@ static int dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp, struct address_space *mapping = vma->vm_file->f_mapping; unsigned long pmd_addr = vmf->address & PMD_MASK; bool write = vmf->flags & FAULT_FLAG_WRITE; + bool sync; unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT; struct inode *inode = mapping->host; int result = VM_FAULT_FALLBACK; @@ -1371,6 +1390,8 @@ static int dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp, if (iomap.offset + iomap.length < pos + PMD_SIZE) goto finish_iomap; + sync = (vma->vm_flags & VM_SYNC) && (iomap.flags & IOMAP_F_DIRTY); + switch (iomap.type) { case IOMAP_MAPPED: error = dax_iomap_pfn(&iomap, pos, PMD_SIZE, &pfn); @@ -1379,10 +1400,24 @@ static int dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp, entry = dax_insert_mapping_entry(mapping, vmf, entry, dax_iomap_sector(&iomap, pos), - RADIX_DAX_PMD, write); + RADIX_DAX_PMD, write && !sync); if (IS_ERR(entry)) goto finish_iomap; + /* + * If we are doing synchronous page fault and inode needs fsync, + * we can insert PMD into page tables only after that happens. + * Skip insertion for now and return the pfn so that caller can + * insert it after fsync is done. + */ + if (sync) { + if (WARN_ON_ONCE(!pfnp)) + goto finish_iomap; + *pfnp = pfn; + result = VM_FAULT_NEEDDSYNC; + goto finish_iomap; + } + trace_dax_pmd_insert_mapping(inode, vmf, PMD_SIZE, pfn, entry); result = vmf_insert_pfn_pmd(vma, vmf->address, vmf->pmd, pfn, write); -- cgit