-
Jan Kara authored
commit 5052b069 upstream. Commit b685d3d6 "block: treat REQ_FUA and REQ_PREFLUSH as synchronous" removed REQ_SYNC flag from WRITE_FUA implementation. Since JBD2 strips REQ_FUA and REQ_FLUSH flags from submitted IO when the filesystem is mounted with nobarrier mount option, journal superblock writes ended up being async writes after this patch and that caused heavy performance regression for dbench4 benchmark with high number of processes. In my test setup with HP RAID array with non-volatile write cache and 32 GB ram, dbench4 runs with 8 processes regressed by ~25%. Fix the problem by making sure journal superblock writes are always treated as synchronous since they generally block progress of the journalling machinery and thus the whole filesystem. Fixes: b685d3d6Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
7621cb79