[PATCH v7 20/38] api-lockfile: document edge cases
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From: Michael Haggerty <hidden>
Date: 2016-06-15 23:02:37
Subsystem:
documentation, the rest · Maintainers:
Jonathan Corbet, Linus Torvalds
Revision v7 of 6 in this series.
Revisions (6)
* Document the behavior of commit_lock_file() when it fails, namely that it rolls back the lock_file object and sets errno appropriately. * Document the behavior of rollback_lock_file() when called for a lock_file object that has already been committed or rolled back, namely that it is a NOOP. Signed-off-by: Michael Haggerty <redacted> --- Documentation/technical/api-lockfile.txt | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-)
diff --git a/Documentation/technical/api-lockfile.txt b/Documentation/technical/api-lockfile.txt
index d3bf940..9805da0 100644
--- a/Documentation/technical/api-lockfile.txt
+++ b/Documentation/technical/api-lockfile.txt@@ -100,6 +100,10 @@ unable_to_lock_die:: Emit an appropriate error message and `die()`. +Similarly, `commit_lock_file` and `close_lock_file` return 0 on +success. On failure they set `errno` appropriately, do their best to +roll back the lockfile, and return -1. + Flags -----
@@ -144,18 +148,22 @@ commit_lock_file:: Take a pointer to the `struct lock_file` initialized with an earlier call to `hold_lock_file_for_update` or - `hold_lock_file_for_append`, close the file descriptor and + `hold_lock_file_for_append`, close the file descriptor, and rename the lockfile to its final destination. Return 0 upon - success or a negative value on failure to `close(2)` or - `rename(2)`. It is a bug to call `commit_lock_file()` for a - `lock_file` object that is not currently locked. + success. On failure, roll back the lock file and return -1, + with `errno` set to the value from the failing call to + `close(2)` or `rename(2)`. It is a bug to call + `commit_lock_file` for a `lock_file` object that is not + currently locked. rollback_lock_file:: Take a pointer to the `struct lock_file` initialized with an earlier call to `hold_lock_file_for_update` or `hold_lock_file_for_append`, close the file descriptor and - remove the lockfile. + remove the lockfile. It is a NOOP to call + `rollback_lock_file()` for a `lock_file` object that has + already been committed or rolled back. close_lock_file::
@@ -163,7 +171,7 @@ close_lock_file:: earlier call to `hold_lock_file_for_update` or `hold_lock_file_for_append`, and close the file descriptor. Return 0 upon success. On failure to `close(2)`, return a - negative value and rollback the lock file. Usually + negative value and roll back the lock file. Usually `commit_lock_file` or `rollback_lock_file` should eventually be called if `close_lock_file` succeeds.
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2.1.0