From fb5c53ea65b75c67c23f90ebbbb1134a5bb6c140 Mon Sep 17 00:00:00 2001 From: John Layman Date: Tue, 13 Aug 2013 15:24:58 -0400 Subject: [PATCH] Fix for re-reading /etc/mtab in zfs_is_mounted() When /etc/mtab is updated on Linux it's done atomically with rename(2). A new mtab is written, the existing mtab is unlinked, and the new mtab is renamed to /etc/mtab. This means that we must close the old file and open the new file to get the updated contents. Using rewind(3) will just move the file pointer back to the start of the file, freopen(3) will close and open the file. Signed-off-by: Brian Behlendorf Closes #1611 --- lib/libzfs/libzfs_dataset.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) diff --git a/lib/libzfs/libzfs_dataset.c b/lib/libzfs/libzfs_dataset.c index 554b0eadc2..244b687edd 100644 --- a/lib/libzfs/libzfs_dataset.c +++ b/lib/libzfs/libzfs_dataset.c @@ -629,12 +629,15 @@ libzfs_mnttab_init(libzfs_handle_t *hdl) sizeof (mnttab_node_t), offsetof(mnttab_node_t, mtn_node)); } -void +int libzfs_mnttab_update(libzfs_handle_t *hdl) { struct mnttab entry; - rewind(hdl->libzfs_mnttab); + /* Reopen MNTTAB to prevent reading stale data from open file */ + if (freopen(MNTTAB, "r", hdl->libzfs_mnttab) == NULL) + return (ENOENT); + while (getmntent(hdl->libzfs_mnttab, &entry) == 0) { mnttab_node_t *mtn; @@ -647,6 +650,8 @@ libzfs_mnttab_update(libzfs_handle_t *hdl) mtn->mtn_mt.mnt_mntopts = zfs_strdup(hdl, entry.mnt_mntopts); avl_add(&hdl->libzfs_mnttab_cache, mtn); } + + return (0); } void @@ -677,13 +682,18 @@ libzfs_mnttab_find(libzfs_handle_t *hdl, const char *fsname, { mnttab_node_t find; mnttab_node_t *mtn; + int error; if (!hdl->libzfs_mnttab_enable) { struct mnttab srch = { 0 }; if (avl_numnodes(&hdl->libzfs_mnttab_cache)) libzfs_mnttab_fini(hdl); - rewind(hdl->libzfs_mnttab); + + /* Reopen MNTTAB to prevent reading stale data from open file */ + if (freopen(MNTTAB, "r", hdl->libzfs_mnttab) == NULL) + return (ENOENT); + srch.mnt_special = (char *)fsname; srch.mnt_fstype = MNTTYPE_ZFS; if (getmntany(hdl->libzfs_mnttab, entry, &srch) == 0) @@ -693,7 +703,8 @@ libzfs_mnttab_find(libzfs_handle_t *hdl, const char *fsname, } if (avl_numnodes(&hdl->libzfs_mnttab_cache) == 0) - libzfs_mnttab_update(hdl); + if ((error = libzfs_mnttab_update(hdl)) != 0) + return (error); find.mtn_mt.mnt_special = (char *)fsname; mtn = avl_find(&hdl->libzfs_mnttab_cache, &find, NULL);