mirror_zfs/config/kernel-d-prune-aliases.m4
Brian Behlendorf 218b4e0a76 Add zfs_sb_prune_aliases() function
For kernels which do not implement a per-suberblock shrinker,
those older than Linux 3.1, the shrink_dcache_parent() function
was used to attempt to reclaim dentries.  This was found not be
entirely reliable and could lead to performance issues on older
kernels running meta-data heavy workloads.

To address this issue a zfs_sb_prune_aliases() function has been
added to implement this functionality.  It relies on traversing
the list of znodes for a filesystem and adding them to a private
list with a reference held.  The private list can then be safely
walked outside the z_znodes_lock to prune dentires and drop the
last reference so the inode can be freed.

This provides the same synchronous behavior as the per-filesystem
shrinker and has the advantage of depending on only long standing
interfaces.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Closes #3501
2015-06-22 10:22:49 -07:00

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dnl #
dnl # 2.6.12 API change
dnl # d_prune_aliases() helper function available.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_D_PRUNE_ALIASES],
[AC_MSG_CHECKING([whether d_prune_aliases() is available])
ZFS_LINUX_TRY_COMPILE_SYMBOL([
#include <linux/dcache.h>
], [
struct inode *ip = NULL;
d_prune_aliases(ip);
], [d_prune_aliases], [fs/dcache.c], [
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_D_PRUNE_ALIASES, 1,
[d_prune_aliases() is available])
], [
AC_MSG_RESULT(no)
])
])