| Message ID | 1475874544-24842-14-git-send-email-ross.zwisler@linux.intel.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
On Fri, Oct 07, 2016 at 03:09:00PM -0600, Ross Zwisler wrote: > Currently iomap_end() doesn't do anything for DAX page faults for both ext2 > and XFS. ext2_iomap_end() just checks for a write underrun, and > xfs_file_iomap_end() checks to see if it needs to finish a delayed > allocation. However, in the future iomap_end() calls might be needed to > make sure we have balanced allocations, locks, etc. So, add calls to > iomap_end() with appropriate error handling to dax_iomap_fault(). Is there a way to just have a single call to iomap_end at the end of the function, after which we just return a previosuly setup return value? e.g. out: if (ops->iomap_end) { error = ops->iomap_end(inode, pos, PAGE_SIZE, PAGE_SIZE, flags, &iomap); } if (error == -ENOMEM) return VM_FAULT_OOM | major; if (error < 0 && error != -EBUSY) return VM_FAULT_SIGBUS | major; return ret;
On Mon, Oct 10, 2016 at 05:50:04PM +0200, Christoph Hellwig wrote: > On Fri, Oct 07, 2016 at 03:09:00PM -0600, Ross Zwisler wrote: > > Currently iomap_end() doesn't do anything for DAX page faults for both ext2 > > and XFS. ext2_iomap_end() just checks for a write underrun, and > > xfs_file_iomap_end() checks to see if it needs to finish a delayed > > allocation. However, in the future iomap_end() calls might be needed to > > make sure we have balanced allocations, locks, etc. So, add calls to > > iomap_end() with appropriate error handling to dax_iomap_fault(). > > Is there a way to just have a single call to iomap_end at the end of > the function, after which we just return a previosuly setup return > value? > > e.g. > > out: > if (ops->iomap_end) { > error = ops->iomap_end(inode, pos, PAGE_SIZE, > PAGE_SIZE, flags, &iomap); > } > > if (error == -ENOMEM) > return VM_FAULT_OOM | major; > if (error < 0 && error != -EBUSY) > return VM_FAULT_SIGBUS | major; > return ret; Sure, will do.
On Fri 07-10-16 15:09:00, Ross Zwisler wrote: > Currently iomap_end() doesn't do anything for DAX page faults for both ext2 > and XFS. ext2_iomap_end() just checks for a write underrun, and > xfs_file_iomap_end() checks to see if it needs to finish a delayed > allocation. However, in the future iomap_end() calls might be needed to > make sure we have balanced allocations, locks, etc. So, add calls to > iomap_end() with appropriate error handling to dax_iomap_fault(). > > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> > Suggested-by: Jan Kara <jack@suse.cz> ... > @@ -1239,6 +1253,17 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf, > break; > } > > + finish_iomap: > + if (ops->iomap_end) { > + if (error) { > + /* keep previous error */ > + ops->iomap_end(inode, pos, PAGE_SIZE, PAGE_SIZE, flags, > + &iomap); I think for the error case we should set number of 'written' bytes to 0 to tell fs to cancel what it has prepared. This is mostly cosmetic since the only case where I can imagine this would matter is shared write fault and in that case we have currently no error path but still it could bite us in the future. Other than that the patch looks good so you can add: Reviewed-by: Jan Kara <jack@suse.cz> Honza
diff --git a/fs/dax.c b/fs/dax.c index 7689ab0..5e8febe 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -1187,7 +1187,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf, goto unlock_entry; if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) { error = -EIO; /* fs corruption? */ - goto unlock_entry; + goto finish_iomap; } sector = dax_iomap_sector(&iomap, pos); @@ -1209,7 +1209,14 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf, } if (error) - goto unlock_entry; + goto finish_iomap; + + if (ops->iomap_end) { + error = ops->iomap_end(inode, pos, PAGE_SIZE, + PAGE_SIZE, flags, &iomap); + if (error) + goto unlock_entry; + } if (!radix_tree_exceptional_entry(entry)) { vmf->page = entry; return VM_FAULT_LOCKED; @@ -1230,8 +1237,15 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf, break; case IOMAP_UNWRITTEN: case IOMAP_HOLE: - if (!(vmf->flags & FAULT_FLAG_WRITE)) + if (!(vmf->flags & FAULT_FLAG_WRITE)) { + if (ops->iomap_end) { + error = ops->iomap_end(inode, pos, PAGE_SIZE, + PAGE_SIZE, flags, &iomap); + if (error) + goto unlock_entry; + } return dax_load_hole(mapping, entry, vmf); + } /*FALLTHRU*/ default: WARN_ON_ONCE(1); @@ -1239,6 +1253,17 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf, break; } + finish_iomap: + if (ops->iomap_end) { + if (error) { + /* keep previous error */ + ops->iomap_end(inode, pos, PAGE_SIZE, PAGE_SIZE, flags, + &iomap); + } else { + error = ops->iomap_end(inode, pos, PAGE_SIZE, + PAGE_SIZE, flags, &iomap); + } + } unlock_entry: put_locked_mapping_entry(mapping, vmf->pgoff, entry); out:
Currently iomap_end() doesn't do anything for DAX page faults for both ext2 and XFS. ext2_iomap_end() just checks for a write underrun, and xfs_file_iomap_end() checks to see if it needs to finish a delayed allocation. However, in the future iomap_end() calls might be needed to make sure we have balanced allocations, locks, etc. So, add calls to iomap_end() with appropriate error handling to dax_iomap_fault(). Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Suggested-by: Jan Kara <jack@suse.cz> --- fs/dax.c | 31 ++++++++++++++++++++++++++++--- 1 file changed, 28 insertions(+), 3 deletions(-)