svn commit: r326427 - stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs

[Andriy Gapon]

Author: avg
Date: Fri Dec  1 11:13:58 2017
New Revision: 326427
URL: https://svnweb.freebsd.org/changeset/base/326427

Log:
  MFC r326070: zfs_write: fix problem with writes appearing to succeed when over quota
  
  The problem happens when the writes have offsets and sizes aligned with
  a filesystem's recordsize (maximum block size).  In this scenario
  dmu_tx_assign() would fail because of being over the quota, but the uio
  would already be modified in the code path where we copy data from the
  uio into a borrowed ARC buffer.  That makes an appearance of a partial
  write, so zfs_write() would return success and the uio would be modified
  consistently with writing a single block.
  
  That bug can result in a data loss because the writes over the quota
  would appear to succeed while the actual data is being discarded.
  
  This commit fixes the bug by ensuring that the uio is not changed until
  after all error checks are done.  To achieve that the code now uses
  uiocopy() + uioskip() as in the original illumos design.  We can do that
  now that uiocopy() has been updated in r326067 to use
  vn_io_fault_uiomove().

Modified:
  stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c
==============================================================================
--- stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c	Fri Dec  1 11:11:25 2017	(r326426)
+++ stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c	Fri Dec  1 11:13:58 2017	(r326427)
@@ -1036,31 +1036,18 @@ zfs_write(vnode_t *vp, uio_t *uio, int ioflag, cred_t 
 			 * holding up the transaction if the data copy hangs
 			 * up on a pagefault (e.g., from an NFS server mapping).
 			 */
-#ifdef illumos
 			size_t cbytes;
-#endif
 
 			abuf = dmu_request_arcbuf(sa_get_db(zp->z_sa_hdl),
 			    max_blksz);
 			ASSERT(abuf != NULL);
 			ASSERT(arc_buf_size(abuf) == max_blksz);
-#ifdef illumos
 			if (error = uiocopy(abuf->b_data, max_blksz,
 			    UIO_WRITE, uio, &cbytes)) {
 				dmu_return_arcbuf(abuf);
 				break;
 			}
 			ASSERT(cbytes == max_blksz);
-#else
-			ssize_t resid = uio->uio_resid;
-			error = vn_io_fault_uiomove(abuf->b_data, max_blksz, uio);
-			if (error != 0) {
-				uio->uio_offset -= resid - uio->uio_resid;
-				uio->uio_resid = resid;
-				dmu_return_arcbuf(abuf);
-				break;
-			}
-#endif
 		}
 
 		/*
@@ -1138,10 +1125,8 @@ zfs_write(vnode_t *vp, uio_t *uio, int ioflag, cred_t 
 				dmu_assign_arcbuf(sa_get_db(zp->z_sa_hdl),
 				    woff, abuf, tx);
 			}
-#ifdef illumos
 			ASSERT(tx_bytes <= uio->uio_resid);
 			uioskip(uio, tx_bytes);
-#endif
 		}
 		if (tx_bytes && vn_has_cached_data(vp)) {
 			update_pages(vp, woff, tx_bytes, zfsvfs->z_os,