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Fix false ENOENT on snapshot control dentries

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Lookups in the snapshot control directory for an existing snapshot
fail with ENOENT if an earlier lookup failed before the snapshot was
created.  This is because the earlier lookup causes a negative dentry
to be cached which is never invalidated.

The bug can be reproduced as follows (the second ls should succeed):

 $ ls /tank/.zfs/snapshot/s
 ls: cannot access /tank/.zfs/snapshot/s: No such file or directory
 $ zfs snap tank@s
 $ ls /tank/.zfs/snapshot/s
 ls: cannot access /tank/.zfs/snapshot/s: No such file or directory

To remedy this, always invalidate cached dentries in the snapshot
control directory.  Since these entries never exist on disk there is
no significant performance penalty for the extra lookups.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1192
This commit is contained in:
Ned Bass
2013-01-14 13:59:14 -08:00
committed by Brian Behlendorf
parent 94a9bb4709
commit f1a05fa114
4 changed files with 158 additions and 58 deletions
Download Patch File Download Diff File Expand all files Collapse all files
config/kernel-dentry-operations.m4
+64
View File
@@ -0,0 +1,64 @@
dnl #
dnl # 3.6 API change
dnl #
AC_DEFUN([ZFS_AC_KERNEL_D_REVALIDATE_NAMEIDATA], [
AC_MSG_CHECKING([whether dops->d_revalidate() takes struct nameidata])
ZFS_LINUX_TRY_COMPILE([
#include <linux/dcache.h>
],[
int (*revalidate) (struct dentry *, struct nameidata *) = NULL;
struct dentry_operations dops __attribute__ ((unused)) = {
.d_revalidate = revalidate,
};
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_D_REVALIDATE_NAMEIDATA, 1,
[dops->d_revalidate() operation takes nameidata])
],[
AC_MSG_RESULT(no)
])
])
dnl #
dnl # 2.6.30 API change
dnl # The 'struct dentry_operations' was constified in the dentry structure.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_CONST_DENTRY_OPERATIONS], [
AC_MSG_CHECKING([whether dentry uses const struct dentry_operations])
ZFS_LINUX_TRY_COMPILE([
#include <linux/dcache.h>
const struct dentry_operations test_d_op = {
.d_revalidate = NULL,
};
],[
struct dentry d __attribute__ ((unused));
d.d_op = &test_d_op;
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_CONST_DENTRY_OPERATIONS, 1,
[dentry uses const struct dentry_operations])
],[
AC_MSG_RESULT(no)
])
])
dnl #
dnl # 2.6.38 API change
dnl # Added d_set_d_op() helper function.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_D_SET_D_OP],
[AC_MSG_CHECKING([whether d_set_d_op() is available])
ZFS_LINUX_TRY_COMPILE_SYMBOL([
#include <linux/dcache.h>
], [
d_set_d_op(NULL, NULL);
], [d_set_d_op], [fs/dcache.c], [
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_D_SET_D_OP, 1,
[d_set_d_op() is available])
], [
AC_MSG_RESULT(no)
])
])
config/kernel.m4
+3
View File
@@ -62,6 +62,9 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
ZFS_AC_KERNEL_INSERT_INODE_LOCKED
ZFS_AC_KERNEL_D_MAKE_ROOT
ZFS_AC_KERNEL_D_OBTAIN_ALIAS
ZFS_AC_KERNEL_D_SET_D_OP
ZFS_AC_KERNEL_D_REVALIDATE_NAMEIDATA
ZFS_AC_KERNEL_CONST_DENTRY_OPERATIONS
ZFS_AC_KERNEL_CHECK_DISK_SIZE_CHANGE
ZFS_AC_KERNEL_TRUNCATE_SETSIZE
ZFS_AC_KERNEL_6ARGS_SECURITY_INODE_INIT_SECURITY