gfs2: Per-revoke accounting in transactions
In the log, revokes are stored as a revoke descriptor (struct
gfs2_log_descriptor), followed by zero or more additional revoke blocks
(struct gfs2_meta_header). On filesystems with a blocksize of 4k, the
revoke descriptor contains up to 503 revokes, and the metadata blocks
contain up to 509 revokes each. We've so far been reserving space for
revokes in transactions in block granularity, so a lot more space than
necessary was being allocated and then released again.
This patch switches to assigning revokes to transactions individually
instead. Initially, space for the revoke descriptor is reserved and
handed out to transactions. When more revokes than that are reserved,
additional revoke blocks are added. When the log is flushed, the space
for the additional revoke blocks is released, but we keep the space for
the revoke descriptor block allocated.
Transactions may still reserve more revokes than they will actually need
in the end, but now we won't overshoot the target as much, and by only
returning the space for excess revokes at log flush time, we further
reduce the amount of contention between processes.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
diff --git a/fs/gfs2/log.h b/fs/gfs2/log.h
index e7f4a8d..eea5801 100644
--- a/fs/gfs2/log.h
+++ b/fs/gfs2/log.h
@@ -74,8 +74,12 @@ extern void gfs2_ordered_del_inode(struct gfs2_inode *ip);
extern unsigned int gfs2_struct2blk(struct gfs2_sbd *sdp, unsigned int nstruct);
extern void gfs2_remove_from_ail(struct gfs2_bufdata *bd);
extern bool gfs2_log_is_empty(struct gfs2_sbd *sdp);
+extern void gfs2_log_release_revokes(struct gfs2_sbd *sdp, unsigned int revokes);
extern void gfs2_log_release(struct gfs2_sbd *sdp, unsigned int blks);
-extern void gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks);
+extern bool gfs2_log_try_reserve(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
+ unsigned int *extra_revokes);
+extern void gfs2_log_reserve(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
+ unsigned int *extra_revokes);
extern void gfs2_write_log_header(struct gfs2_sbd *sdp, struct gfs2_jdesc *jd,
u64 seq, u32 tail, u32 lblock, u32 flags,
int op_flags);