This problem can occur when multiple cluster services fail over at the same time, causing missing high-available exports. Having a lot of nfs-exports will trigger this issue easier. https://bugzilla.linux-nfs.org/show_bug.cgi?id=224 Signed-off-by: Steve Dickson <steved@xxxxxxxxxx> --- support/include/exportfs.h | 4 ++++ utils/exportfs/exportfs.c | 41 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 45 insertions(+), 0 deletions(-) diff --git a/support/include/exportfs.h b/support/include/exportfs.h index 01e87dd..99916e5 100644 --- a/support/include/exportfs.h +++ b/support/include/exportfs.h @@ -32,6 +32,10 @@ enum { FSLOC_STUB }; +#ifndef EXP_LOCKFILE +#define EXP_LOCKFILE "/var/lib/nfs/export-lock" +#endif + typedef struct mclient { struct mclient * m_next; char * m_hostname; diff --git a/utils/exportfs/exportfs.c b/utils/exportfs/exportfs.c index 7432a65..7326802 100644 --- a/utils/exportfs/exportfs.c +++ b/utils/exportfs/exportfs.c @@ -16,6 +16,7 @@ #include <sys/stat.h> #include <sys/vfs.h> #include <sys/stat.h> +#include <sys/file.h> #include <unistd.h> #include <stdbool.h> #include <stdlib.h> @@ -44,6 +45,39 @@ static void validate_export(nfs_export *exp); static int matchhostname(const char *hostname1, const char *hostname2); static void export_d_read(const char *dname); +static const char *lockfile = EXP_LOCKFILE; +static int _lockfd = -1; + +/* + * If we aren't careful, changes made by exportfs can be lost + * when multiple exports process run at once: + * + * exportfs process 1 exportfs process 2 + * ------------------------------------------ + * reads etab version A reads etab version A + * adds new export B adds new export C + * writes A+B writes A+C + * + * The locking in support/export/xtab.c will prevent mountd from + * seeing a partially written version of etab, and will prevent + * the two writers above from writing simultaneously and + * corrupting etab, but to prevent problems like the above we + * need these additional lockfile() routines. + */ +void +grab_lockfile() +{ + _lockfd = open(lockfile, O_CREAT|O_RDWR, 0666); + if (_lockfd != -1) + lockf(_lockfd, F_LOCK, 0); +} +void +release_lockfile() +{ + if (_lockfd != -1) + lockf(_lockfd, F_ULOCK, 0); +} + int main(int argc, char **argv) { @@ -129,6 +163,13 @@ main(int argc, char **argv) return 0; } } + + /* + * Serialize things as best we can + */ + grab_lockfile(); + atexit(release_lockfile); + if (f_export && ! f_ignore) { export_read(_PATH_EXPORTS); export_d_read(_PATH_EXPORTS_D); -- 1.7.7.5 -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
