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dax: Call ->iomap_begin without entry lock during dax fault
Currently ->iomap_begin() handler is called with entry lock held. If the filesystem held any locks between ->iomap_begin() and ->iomap_end() (such as ext4 which will want to hold transaction open), this would cause lock inversion with the iomap_apply() from standard IO path which first calls ->iomap_begin() and only then calls ->actor() callback which grabs entry locks for DAX (if it faults when copying from/to user provided buffers). Fix the problem by nesting grabbing of entry lock inside ->iomap_begin() - ->iomap_end() pair. Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Jan Kara
Dan Williams
parent
f449b936f1
commit
9f141d6ef6
123
fs/dax.c
123
fs/dax.c
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@ -1078,6 +1078,15 @@ dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
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}
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EXPORT_SYMBOL_GPL(dax_iomap_rw);
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static int dax_fault_return(int error)
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{
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if (error == 0)
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return VM_FAULT_NOPAGE;
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if (error == -ENOMEM)
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return VM_FAULT_OOM;
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return VM_FAULT_SIGBUS;
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}
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/**
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* dax_iomap_fault - handle a page fault on a DAX file
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* @vma: The virtual memory area where the fault occurred
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@ -1110,12 +1119,6 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
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if (pos >= i_size_read(inode))
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return VM_FAULT_SIGBUS;
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entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
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if (IS_ERR(entry)) {
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error = PTR_ERR(entry);
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goto out;
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}
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if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page)
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flags |= IOMAP_WRITE;
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@ -1126,9 +1129,15 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
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*/
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error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap);
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if (error)
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goto unlock_entry;
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return dax_fault_return(error);
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if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
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error = -EIO; /* fs corruption? */
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vmf_ret = dax_fault_return(-EIO); /* fs corruption? */
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goto finish_iomap;
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}
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entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
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if (IS_ERR(entry)) {
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vmf_ret = dax_fault_return(PTR_ERR(entry));
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goto finish_iomap;
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}
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@ -1151,13 +1160,13 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
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}
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if (error)
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goto finish_iomap;
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goto error_unlock_entry;
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__SetPageUptodate(vmf->cow_page);
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vmf_ret = finish_fault(vmf);
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if (!vmf_ret)
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vmf_ret = VM_FAULT_DONE_COW;
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goto finish_iomap;
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goto unlock_entry;
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}
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switch (iomap.type) {
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@ -1169,12 +1178,15 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
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}
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error = dax_insert_mapping(mapping, iomap.bdev, sector,
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PAGE_SIZE, &entry, vma, vmf);
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/* -EBUSY is fine, somebody else faulted on the same PTE */
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if (error == -EBUSY)
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error = 0;
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break;
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case IOMAP_UNWRITTEN:
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case IOMAP_HOLE:
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if (!(vmf->flags & FAULT_FLAG_WRITE)) {
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vmf_ret = dax_load_hole(mapping, &entry, vmf);
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goto finish_iomap;
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goto unlock_entry;
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}
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/*FALLTHRU*/
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default:
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@ -1183,30 +1195,25 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
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break;
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}
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finish_iomap:
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if (ops->iomap_end) {
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if (error || (vmf_ret & VM_FAULT_ERROR)) {
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/* keep previous error */
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ops->iomap_end(inode, pos, PAGE_SIZE, 0, flags,
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&iomap);
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} else {
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error = ops->iomap_end(inode, pos, PAGE_SIZE,
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PAGE_SIZE, flags, &iomap);
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}
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}
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error_unlock_entry:
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vmf_ret = dax_fault_return(error) | major;
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unlock_entry:
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put_locked_mapping_entry(mapping, vmf->pgoff, entry);
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out:
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if (error == -ENOMEM)
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return VM_FAULT_OOM | major;
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/* -EBUSY is fine, somebody else faulted on the same PTE */
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if (error < 0 && error != -EBUSY)
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return VM_FAULT_SIGBUS | major;
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if (vmf_ret) {
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WARN_ON_ONCE(error); /* -EBUSY from ops->iomap_end? */
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return vmf_ret;
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finish_iomap:
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if (ops->iomap_end) {
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int copied = PAGE_SIZE;
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if (vmf_ret & VM_FAULT_ERROR)
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copied = 0;
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/*
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* The fault is done by now and there's no way back (other
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* thread may be already happily using PTE we have installed).
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* Just ignore error from ->iomap_end since we cannot do much
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* with it.
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*/
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ops->iomap_end(inode, pos, PAGE_SIZE, copied, flags, &iomap);
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}
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return VM_FAULT_NOPAGE | major;
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return vmf_ret;
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}
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EXPORT_SYMBOL_GPL(dax_iomap_fault);
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@ -1330,16 +1337,6 @@ int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
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if ((pgoff | PG_PMD_COLOUR) > max_pgoff)
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goto fallback;
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/*
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* grab_mapping_entry() will make sure we get a 2M empty entry, a DAX
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* PMD or a HZP entry. If it can't (because a 4k page is already in
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* the tree, for instance), it will return -EEXIST and we just fall
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* back to 4k entries.
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*/
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entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
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if (IS_ERR(entry))
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goto fallback;
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/*
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* Note that we don't use iomap_apply here. We aren't doing I/O, only
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* setting up a mapping, so really we're using iomap_begin() as a way
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@ -1348,10 +1345,21 @@ int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
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pos = (loff_t)pgoff << PAGE_SHIFT;
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error = ops->iomap_begin(inode, pos, PMD_SIZE, iomap_flags, &iomap);
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if (error)
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goto unlock_entry;
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goto fallback;
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if (iomap.offset + iomap.length < pos + PMD_SIZE)
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goto finish_iomap;
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/*
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* grab_mapping_entry() will make sure we get a 2M empty entry, a DAX
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* PMD or a HZP entry. If it can't (because a 4k page is already in
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* the tree, for instance), it will return -EEXIST and we just fall
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* back to 4k entries.
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*/
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entry = grab_mapping_entry(mapping, pgoff, RADIX_DAX_PMD);
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if (IS_ERR(entry))
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goto finish_iomap;
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vmf.pgoff = pgoff;
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vmf.flags = flags;
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vmf.gfp_mask = mapping_gfp_mask(mapping) | __GFP_IO;
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@ -1364,7 +1372,7 @@ int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
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case IOMAP_UNWRITTEN:
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case IOMAP_HOLE:
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if (WARN_ON_ONCE(write))
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goto finish_iomap;
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goto unlock_entry;
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result = dax_pmd_load_hole(vma, pmd, &vmf, address, &iomap,
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&entry);
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break;
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@ -1373,20 +1381,23 @@ int dax_iomap_pmd_fault(struct vm_area_struct *vma, unsigned long address,
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break;
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}
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finish_iomap:
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if (ops->iomap_end) {
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if (result == VM_FAULT_FALLBACK) {
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ops->iomap_end(inode, pos, PMD_SIZE, 0, iomap_flags,
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&iomap);
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} else {
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error = ops->iomap_end(inode, pos, PMD_SIZE, PMD_SIZE,
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iomap_flags, &iomap);
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if (error)
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result = VM_FAULT_FALLBACK;
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}
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}
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unlock_entry:
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put_locked_mapping_entry(mapping, pgoff, entry);
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finish_iomap:
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if (ops->iomap_end) {
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int copied = PMD_SIZE;
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if (result == VM_FAULT_FALLBACK)
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copied = 0;
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/*
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* The fault is done by now and there's no way back (other
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* thread may be already happily using PMD we have installed).
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* Just ignore error from ->iomap_end since we cannot do much
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* with it.
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*/
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ops->iomap_end(inode, pos, PMD_SIZE, copied, iomap_flags,
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&iomap);
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}
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fallback:
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if (result == VM_FAULT_FALLBACK) {
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split_huge_pmd(vma, pmd, address);
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