Currently, the only visibility into filesystem freeze or
thaw activity is when an error is returned from the actual
call to freeze or thaw. If the action itself hangs, there
is no indication that the freeze or thaw was in-progress,
short of collecting a vmcore.
There is also no record of what process froze a filesystem
or when it happened, so if the process does not thaw it
later, debugging the issue is difficult.
These patches add tracepoints to the generic filesystem
freeze and thaw functions. When enabled, trace events
will create a record of these activities.
Sample trace events:
(freeze /dev/vdd)
fsfreeze-23072 [003] .... 1018126.904878: freeze_super_enter: comm=fsfreeze pid=23072 for xfs filesystem 'vdd' (253:48) frozen=0
fsfreeze-23072 [003] .... 1018126.926173: freeze_super_exit: comm=fsfreeze pid=23072 for xfs filesystem 'vdd' (253:48) frozen=4 ret=0
(thaw /dev/vdd)
<...>-23074 [000] .... 1018134.025833: thaw_super_enter: comm=fsfreeze pid=23074 for xfs filesystem 'vdd' (253:48) frozen=4
<...>-23074 [000] .... 1018134.025873: thaw_super_exit: comm=fsfreeze pid=23074 for xfs filesystem 'vdd' (253:48) frozen=0 ret=0
(freeze /dev/vdb)
fsfreeze-23077 [003] .... 1018162.211518: freeze_super_enter: comm=fsfreeze pid=23077 for ext4 filesystem 'vdb' (253:16) frozen=0
fsfreeze-23077 [003] .... 1018162.228586: freeze_super_exit: comm=fsfreeze pid=23077 for ext4 filesystem 'vdb' (253:16) frozen=4 ret=0
(attempt to freeze already-frozen /dev/vdb)
fsfreeze-23078 [003] .... 1018169.864362: freeze_super_enter: comm=fsfreeze pid=23078 for ext4 filesystem 'vdb' (253:16) frozen=4
fsfreeze-23078 [003] .... 1018169.864385: freeze_super_exit: comm=fsfreeze pid=23078 for ext4 filesystem 'vdb' (253:16) frozen=4 ret=-16
(unfreeze /dev/vdb)
fsfreeze-23079 [003] .... 1018173.074331: thaw_super_enter: comm=fsfreeze pid=23079 for ext4 filesystem 'vdb' (253:16) frozen=4
fsfreeze-23079 [003] .... 1018173.075928: thaw_super_exit: comm=fsfreeze pid=23079 for ext4 filesystem 'vdb' (253:16) frozen=0 ret=0
(attempt to unfreeze already unfrozen /dev/vdb)
fsfreeze-23080 [000] .... 1018175.105613: thaw_super_enter: comm=fsfreeze pid=23080 for ext4 filesystem 'vdb' (253:16) frozen=0
fsfreeze-23080 [000] .... 1018175.105639: thaw_super_exit: comm=fsfreeze pid=23080 for ext4 filesystem 'vdb' (253:16) frozen=0 ret=22
Frank Sorenson (5):
fs: simplify freeze_super()/thaw_super() exit handling
fs/block_dev.c: simplify freeze_bdev() and thaw_bdev() exit handling
fs: add trace events for freeze_super() and thaw_super()
fs/block_dev.c: add trace events for freeze_bdev() and
thaw_bdev()
fs: enable filesystem freeze/thaw events
fs/block_dev.c | 30 +++++---
fs/super.c | 54 ++++++++------
include/trace/events/fs.h | 109 +++++++++++++++++++++++++++++
include/trace/events/fs_bdev.h | 155 +++++++++++++++++++++++++++++++++++++++++
4 files changed, 316 insertions(+), 32 deletions(-)
create mode 100644 include/trace/events/fs.h
create mode 100644 include/trace/events/fs_bdev.h
--
1.8.3.1
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