diff options
| -rw-r--r-- | doc/legacy/hacker-guide/lock-ahead.txt | 80 |
1 files changed, 0 insertions, 80 deletions
diff --git a/doc/legacy/hacker-guide/lock-ahead.txt b/doc/legacy/hacker-guide/lock-ahead.txt deleted file mode 100644 index 70aa452d3de..00000000000 --- a/doc/legacy/hacker-guide/lock-ahead.txt +++ /dev/null @@ -1,80 +0,0 @@ - Lock-ahead translator - --------------------- - -The objective of the lock-ahead translator is to speculatively -hold locks (inodelk and entrylk) on the universal set (0 - infinity -in case of inodelk and all basenames in case of entrylk) even -when a lock is requested only on a subset, in anticipation that -further locks will be requested within the same universal set. - -So, for example, when cluster/replicate locks a region before -writing to it, lock-ahead would instead lock the entire file. -On further writes, lock-ahead can immediately return success for -the lock requests, since the entire file has been previously locked. - -To avoid starvation of other clients/mountpoints, we employ a -notify mechanism, described below. - -typedef struct { - struct list_head subset_locks; -} la_universal_lock_t; - -Universal lock structure is stored in the inode context. - -typedef struct { - enum {LOCK_AHEAD_ENTRYLK, LOCK_AHEAD_FENTRYLK, - LOCK_AHEAD_INODELK, LOCK_AHEAD_FINODELK}; - - union { - fd_t *fd; - loc_t loc; - }; - - off_t l_start; - off_t l_len; - - const char *basename; - - struct list_head universal_lock; -} la_subset_lock_t; - - -fops implemented: - -* inodelk/finodelk/entrylk/fentrylk: - -lock: - if universal lock held: - add subset to it (save loc_t or fd) and return success - else: - send lock-notify fop - hold universal lock and return - (set inode context, add subset to it, save loc_t or fd) - - if this fails: - forward the lock request - -unlock: - if subset exists in universal lock: - delete subset lock from list - else: - forward it - -* release: - hold subset locks (each subset lock using the saved loc_t or fd) - and release universal lock - -* lock-notify (on unwind) (new fop) - hold subset locks and release universal lock - - -lock-notify in locks translator: - -if a subset lock in entrylk/inodelk cannot be satisfied -because of a universal lock held by someone else: - unwind the lock-notify fop - -============================================== -$ Last updated: Tue Feb 17 11:31:18 IST 2009 $ -$ Author: Vikas Gorur <vikas@gluster.com> $ -============================================== |