From 5ca4d781d36946de197ed2d4196c84c8f6b4522f Mon Sep 17 00:00:00 2001 From: Ian Kent Date: Mon, 12 Oct 2020 15:40:01 -0400 Subject: [PATCH] xfsprogs: ignore autofs mount table entries Some of the xfsprogs utilities read the mount table via. getmntent(3). The mount table may contain (almost always these days since /etc/mtab is symlinked to /proc/self/mounts) autofs mount entries. During processing of the mount table entries statfs(2) can be called on mount point paths which will trigger an automount if those entries are direct or offset autofs mount triggers (indirect autofs mounts aren't affected). This can be a problem when there are a lot of autofs direct or offset mounts because real mounts will be triggered when statfs(2) is called. This can be particularly bad if the triggered mounts are NFS mounts and the server is unavailable leading to lengthy boot times or worse. Simply ignoring autofs mount entries during getmentent(3) traversals avoids the statfs() call that triggers these mounts. If there are automounted mounts (real mounts) at the time of reading the mount table these will still be seen in the list so they will be included if that actually matters to the reader. Recent glibc getmntent(3) can ignore autofs mounts but that requires the autofs user to configure autofs to use the "ignore" pseudo mount option for autofs mounts. But this isn't yet the autofs default (to prevent unexpected side effects) so that can't be used. The autofs direct and offset automount triggers are pseudo file system mounts and are more or less useless in terms on file system information so excluding them doesn't sacrifice useful file system information either. Consequently excluding autofs mounts shouldn't have any adverse side effects. Changes since v1: - drop hunk from fsr/xfs_fsr.c. Signed-off-by: Ian Kent Reviewed-by: Eric Sandeen Signed-off-by: Eric Sandeen Signed-off-by: Pavel Reichl --- libfrog/linux.c | 2 ++ libfrog/paths.c | 2 ++ 2 files changed, 4 insertions(+) diff --git a/libfrog/linux.c b/libfrog/linux.c index 40a839d1..a45d99ab 100644 --- a/libfrog/linux.c +++ b/libfrog/linux.c @@ -73,6 +73,8 @@ platform_check_mount(char *name, char *block, struct stat *s, int flags) * servers. So first, a simple check: does the "dev" start with "/" ? */ while ((mnt = getmntent(f)) != NULL) { + if (!strcmp(mnt->mnt_type, "autofs")) + continue; if (mnt->mnt_fsname[0] != '/') continue; if (stat(mnt->mnt_dir, &mst) < 0) diff --git a/libfrog/paths.c b/libfrog/paths.c index 32737223..d6793764 100644 --- a/libfrog/paths.c +++ b/libfrog/paths.c @@ -389,6 +389,8 @@ fs_table_initialise_mounts( return errno; while ((mnt = getmntent(mtp)) != NULL) { + if (!strcmp(mnt->mnt_type, "autofs")) + continue; if (!realpath(mnt->mnt_dir, rmnt_dir)) continue; if (!realpath(mnt->mnt_fsname, rmnt_fsname)) -- 2.40.1