diff options
| -rw-r--r-- | fs/ubifs/commit.c | 58 |
1 files changed, 57 insertions, 1 deletions
diff --git a/fs/ubifs/commit.c b/fs/ubifs/commit.c index 02429d81ca33..b148fbc80f8d 100644 --- a/fs/ubifs/commit.c +++ b/fs/ubifs/commit.c @@ -48,6 +48,56 @@ #include <linux/slab.h> #include "ubifs.h" +/* + * nothing_to_commit - check if there is nothing to commit. + * @c: UBIFS file-system description object + * + * This is a helper function which checks if there is anything to commit. It is + * used as an optimization to avoid starting the commit if it is not really + * necessary. Indeed, the commit operation always assumes flash I/O (e.g., + * writing the commit start node to the log), and it is better to avoid doing + * this unnecessarily. E.g., 'ubifs_sync_fs()' runs the commit, but if there is + * nothing to commit, it is more optimal to avoid any flash I/O. + * + * This function has to be called with @c->commit_sem locked for writing - + * this function does not take LPT/TNC locks because the @c->commit_sem + * guarantees that we have exclusive access to the TNC and LPT data structures. + * + * This function returns %1 if there is nothing to commit and %0 otherwise. + */ +static int nothing_to_commit(struct ubifs_info *c) +{ + /* + * During mounting or remounting from R/O mode to R/W mode we may + * commit for various recovery-related reasons. + */ + if (c->mounting || c->remounting_rw) + return 0; + + /* + * If the root TNC node is dirty, we definitely have something to + * commit. + */ + if (c->zroot.znode && test_bit(DIRTY_ZNODE, &c->zroot.znode->flags)) + return 0; + + /* + * Even though the TNC is clean, the LPT tree may have dirty nodes. For + * example, this may happen if the budgeting subsystem invoked GC to + * make some free space, and the GC found an LEB with only dirty and + * free space. In this case GC would just change the lprops of this + * LEB (by turning all space into free space) and unmap it. + */ + if (c->nroot && test_bit(DIRTY_CNODE, &c->nroot->flags)) + return 0; + + ubifs_assert(atomic_long_read(&c->dirty_zn_cnt) == 0); + ubifs_assert(c->dirty_pn_cnt == 0); + ubifs_assert(c->dirty_nn_cnt == 0); + + return 1; +} + /** * do_commit - commit the journal. * @c: UBIFS file-system description object @@ -70,6 +120,12 @@ static int do_commit(struct ubifs_info *c) goto out_up; } + if (nothing_to_commit(c)) { + up_write(&c->commit_sem); + err = 0; + goto out_cancel; + } + /* Sync all write buffers (necessary for recovery) */ for (i = 0; i < c->jhead_cnt; i++) { err = ubifs_wbuf_sync(&c->jheads[i].wbuf); @@ -162,12 +218,12 @@ static int do_commit(struct ubifs_info *c) if (err) goto out; +out_cancel: spin_lock(&c->cs_lock); c->cmt_state = COMMIT_RESTING; wake_up(&c->cmt_wq); dbg_cmt("commit end"); spin_unlock(&c->cs_lock); - return 0; out_up: |