ceph: add diagnostic timeout loop to wait_caps_flush()
Convert wait_caps_flush() from a silent indefinite wait into a diagnostic
wait loop that periodically dumps pending cap flush state.
The underlying wait semantics remain intact: callers still wait until the
requested cap flushes complete. The difference is that long stalls now
produce actionable diagnostics instead of looking like a silent hang.
CEPH_CAP_FLUSH_MAX_DUMP_ENTRIES limits the number of entries
emitted per diagnostic dump, and CEPH_CAP_FLUSH_MAX_DUMP_ITERS
limits the number of timed diagnostic dumps before the wait
continues silently. When more entries exist than the per-dump
limit, a truncation count is reported. When the dump iteration
limit is reached, a final suppression message is emitted so the
transition to silence is explicit.
The diagnostic dump collects flush entry data under cap_dirty_lock into
a bounded on-stack array, then prints after releasing the lock. This
avoids holding the spinlock across printk calls.
A null cf->ci on the global flush list indicates a bug since all
cap_flush entries are initialized with a valid ci before being added.
Signal this with WARN_ON_ONCE while still printing enough context for
debugging.
READ_ONCE is used for the i_last_cap_flush_ack field, which is read
outside the inode lock domain. Flush tids are monotonically increasing
and acks are processed in order under i_ceph_lock, so the latest ack
tid is always the most recently written value.
Add a ci pointer to struct ceph_cap_flush so that the diagnostic
dump can identify which inode each pending flush belongs to. The
new i_last_cap_flush_ack field tracks the latest acknowledged flush
tid per inode for diagnostic correlation.
This improves reset-drain observability and is also useful for
existing sync and writeback troubleshooting paths.
projects / thirdparty / kernel / linux.git / commit
