From a2603d4dd02194a05a550a5759970515b9aa2f08 Mon Sep 17 00:00:00 2001 From: Marc Dionne Date: Thu, 18 Dec 2014 08:43:22 -0500 Subject: [PATCH] Linux: d_splice_alias may drop inode reference on error MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit d_splice_alias now drops the inode reference on error, so we need to grab an extra one to make sure that the inode doesn't go away, and release it when done if there was no error. For kernels that may not drop the reference, provide an additional iput() within an ifdef. This could be hooked up to a configure option to allow building a module for a kernel that is known not to drop the reference on error. That hook is not provided here. Affected kernels should be the early 3.17 ones (3.17 - 3.17.2); 3.16 and older kernels should not return errors here. [kaduk@mit.edu add configure option to control behavior, which is mandatory on non-buildbot linux systems] Reviewed-on: http://gerrit.openafs.org/11643 Tested-by: BuildBot Reviewed-by: Michael Laß Reviewed-by: Jeffrey Altman (cherry picked from commit 15260c7fdc5ac8fe9fb1797c8e383c665e9e0ccd) Change-Id: I288eb66c38386fcd6bae0da111d97e211cc5c995 Reviewed-on: http://gerrit.openafs.org/11694 Tested-by: BuildBot Reviewed-by: Stephan Wiesand --- acinclude.m4 | 26 ++++++++++++++++++++++++++ src/afs/LINUX/osi_vnodeops.c | 29 ++++++++++++++++++++++++++--- 2 files changed, 52 insertions(+), 3 deletions(-) diff --git a/acinclude.m4 b/acinclude.m4 index 11e88e26d..e7b7ae98d 100644 --- a/acinclude.m4 +++ b/acinclude.m4 @@ -232,6 +232,26 @@ AC_ARG_ENABLE([linux-syscall-probing], , [enable_linux_syscall_probing="maybe"]) +AC_ARG_ENABLE([linux-d_splice_alias-extra-iput], + [AS_HELP_STRING([--enable-linux-d_splice_alias-extra-iput], + [Linux has introduced an incompatible behavior change in the + d_splice_alias function with no reliable way to determine which + behavior will be produced. If Linux commit + 51486b900ee92856b977eacfc5bfbe6565028070 (or equivalent) has been + applied to your kernel, disable this option. If that commit is + not present in your kernel, enable this option. We apologize + that you are required to know this about your running kernel.])], + [], + [case $system in + *-linux*) + AS_IF([test "x$LOGNAME" != "xbuildslave" && + test "x$LOGNAME" != "xbuildbot"], + [AC_ERROR([Linux users must specify either + --enable-linux-d_splice_alias-extra-iput or + --disable-linux-d_splice_alias-extra-iput])], + [enable_linux_d_splice_alias_extra_iput="no"]) + esac + ]) AC_ARG_WITH([xslt-processor], AS_HELP_STRING([--with-xslt-processor=ARG], [which XSLT processor to use (possible choices are: libxslt, saxon, xalan-j, xsltproc)]), @@ -925,6 +945,9 @@ case $AFS_SYSNAME in *_linux* | *_umlinux*) AC_CHECK_LINUX_FUNC([hlist_unhashed], [#include ], [hlist_unhashed(0);]) + AC_CHECK_LINUX_FUNC([ihold], + [#include ], + [ihold(NULL);]) AC_CHECK_LINUX_FUNC([i_size_read], [#include ], [i_size_read(NULL);]) @@ -1116,6 +1139,9 @@ case $AFS_SYSNAME in *_linux* | *_umlinux*) fi : fi + if test "x$enable_linux_d_splice_alias_extra_iput" = xyes; then + AC_DEFINE(D_SPLICE_ALIAS_LEAK_ON_ERROR, 1, [for internal use]) + fi dnl Linux-only, but just enable always. AC_DEFINE(AFS_CACHE_BYPASS, 1, [define to activate cache bypassing Unix client]) esac diff --git a/src/afs/LINUX/osi_vnodeops.c b/src/afs/LINUX/osi_vnodeops.c index 216b4e292..f3ca4e35c 100644 --- a/src/afs/LINUX/osi_vnodeops.c +++ b/src/afs/LINUX/osi_vnodeops.c @@ -1548,6 +1548,17 @@ afs_linux_lookup(struct inode *dip, struct dentry *dp) ip->i_flags |= S_AUTOMOUNT; #endif } + /* + * Take an extra reference so the inode doesn't go away if + * d_splice_alias drops our reference on error. + */ + if (ip) +#ifdef HAVE_LINUX_IHOLD + ihold(ip); +#else + igrab(ip); +#endif + newdp = d_splice_alias(ip, dp); done: @@ -1561,14 +1572,26 @@ afs_linux_lookup(struct inode *dip, struct dentry *dp) * d_splice_alias can return an error (EIO) if there is an existing * connected directory alias for this dentry. */ - if (!IS_ERR(newdp)) + if (!IS_ERR(newdp)) { + iput(ip); return newdp; - else { + } else { d_add(dp, ip); + /* + * Depending on the kernel version, d_splice_alias may or may + * not drop the inode reference on error. If it didn't, do it + * here. + */ +#if defined(D_SPLICE_ALIAS_LEAK_ON_ERROR) + iput(ip); +#endif return NULL; } - } else + } else { + if (ip) + iput(ip); return ERR_PTR(afs_convert_code(code)); + } } static int -- 2.39.5