journald: turn off COW for journal files on btrfs

btrfs' COW logic results in heavily fragment journal files, which is
detrimental for perfomance. Hence, turn off COW for journal files as we
create them.

Turning off COW comes at the cost of data integrity guarantees, but this
should be acceptable, given that we do our own checksumming, and
generally have a pretty conservative write pattern.

Also see discussion on linux-btrfs:

http://www.spinics.net/lists/linux-btrfs/msg41001.html

1 files changed, 4 insertions, 8 deletions

diff --git a/src/journal/journalctl.c b/src/journal/journalctl.c
index 386e3505c0..62931f14c9 100644
--- a/src/journal/journalctl.c
+++ b/src/journal/journalctl.c
@@ -1294,7 +1294,7 @@ static int setup_keys(void) {
         size_t mpk_size, seed_size, state_size, i;
         uint8_t *mpk, *seed, *state;
         ssize_t l;
-        int fd = -1, r, attr = 0;
+        int fd = -1, r;
         sd_id128_t machine, boot;
         char *p = NULL, *k = NULL;
         struct FSSHeader h;
@@ -1389,13 +1389,9 @@ static int setup_keys(void) {
 
         /* Enable secure remove, exclusion from dump, synchronous
          * writing and in-place updating */
-        if (ioctl(fd, FS_IOC_GETFLAGS, &attr) < 0)
-                log_warning_errno(errno, "FS_IOC_GETFLAGS failed: %m");
-
-        attr |= FS_SECRM_FL|FS_NODUMP_FL|FS_SYNC_FL|FS_NOCOW_FL;
-
-        if (ioctl(fd, FS_IOC_SETFLAGS, &attr) < 0)
-                log_warning_errno(errno, "FS_IOC_SETFLAGS failed: %m");
+        r = chattr_fd(fd, true, FS_SECRM_FL|FS_NODUMP_FL|FS_SYNC_FL|FS_NOCOW_FL);
+        if (r < 0)
+                log_warning_errno(errno, "Failed to set file attributes: %m");
 
         zero(h);
         memcpy(h.signature, "KSHHRHLP", 8);