diff options
| -rw-r--r-- | Documentation/technical/api-lockfile.txt | 242 | ||||
| -rw-r--r-- | builtin/add.c | 1 | ||||
| -rw-r--r-- | builtin/apply.c | 1 | ||||
| -rw-r--r-- | builtin/checkout-index.c | 2 | ||||
| -rw-r--r-- | builtin/checkout.c | 2 | ||||
| -rw-r--r-- | builtin/clone.c | 1 | ||||
| -rw-r--r-- | builtin/commit.c | 17 | ||||
| -rw-r--r-- | builtin/describe.c | 1 | ||||
| -rw-r--r-- | builtin/diff.c | 1 | ||||
| -rw-r--r-- | builtin/gc.c | 2 | ||||
| -rw-r--r-- | builtin/merge.c | 16 | ||||
| -rw-r--r-- | builtin/mv.c | 2 | ||||
| -rw-r--r-- | builtin/read-tree.c | 1 | ||||
| -rw-r--r-- | builtin/receive-pack.c | 1 | ||||
| -rw-r--r-- | builtin/reflog.c | 4 | ||||
| -rw-r--r-- | builtin/reset.c | 1 | ||||
| -rw-r--r-- | builtin/rm.c | 2 | ||||
| -rw-r--r-- | builtin/update-index.c | 3 | ||||
| -rw-r--r-- | bundle.c | 1 | ||||
| -rw-r--r-- | cache-tree.c | 1 | ||||
| -rw-r--r-- | cache.h | 20 | ||||
| -rw-r--r-- | config.c | 16 | ||||
| -rw-r--r-- | credential-store.c | 1 | ||||
| -rw-r--r-- | fast-import.c | 5 | ||||
| -rw-r--r-- | fetch-pack.c | 1 | ||||
| -rw-r--r-- | lockfile.c | 284 | ||||
| -rw-r--r-- | lockfile.h | 84 | ||||
| -rw-r--r-- | merge-recursive.c | 1 | ||||
| -rw-r--r-- | merge.c | 1 | ||||
| -rw-r--r-- | read-cache.c | 21 | ||||
| -rw-r--r-- | refs.c | 23 | ||||
| -rw-r--r-- | rerere.c | 1 | ||||
| -rw-r--r-- | sequencer.c | 1 | ||||
| -rw-r--r-- | sha1_file.c | 1 | ||||
| -rw-r--r-- | shallow.c | 7 | ||||
| -rw-r--r-- | test-scrap-cache-tree.c | 1 |
36 files changed, 510 insertions, 260 deletions
diff --git a/Documentation/technical/api-lockfile.txt b/Documentation/technical/api-lockfile.txt index dd894043ae..d4484d154d 100644 --- a/Documentation/technical/api-lockfile.txt +++ b/Documentation/technical/api-lockfile.txt @@ -3,20 +3,128 @@ lockfile API The lockfile API serves two purposes: -* Mutual exclusion. When we write out a new index file, first - we create a new file `$GIT_DIR/index.lock`, write the new - contents into it, and rename it to the final destination - `$GIT_DIR/index`. We try to create the `$GIT_DIR/index.lock` - file with O_EXCL so that we can notice and fail when somebody - else is already trying to update the index file. - -* Automatic cruft removal. After we create the "lock" file, we - may decide to `die()`, and we would want to make sure that we - remove the file that has not been committed to its final - destination. This is done by remembering the lockfiles we - created in a linked list and cleaning them up from an - `atexit(3)` handler. Outstanding lockfiles are also removed - when the program dies on a signal. +* Mutual exclusion and atomic file updates. When we want to change a + file, we create a lockfile `<filename>.lock`, write the new file + contents into it, and then rename the lockfile to its final + destination `<filename>`. We create the `<filename>.lock` file with + `O_CREAT|O_EXCL` so that we can notice and fail if somebody else has + already locked the file, then atomically rename the lockfile to its + final destination to commit the changes and unlock the file. + +* Automatic cruft removal. If the program exits after we lock a file + but before the changes have been committed, we want to make sure + that we remove the lockfile. This is done by remembering the + lockfiles we have created in a linked list and setting up an + `atexit(3)` handler and a signal handler that clean up the + lockfiles. This mechanism ensures that outstanding lockfiles are + cleaned up if the program exits (including when `die()` is called) + or if the program dies on a signal. + +Please note that lockfiles only block other writers. Readers do not +block, but they are guaranteed to see either the old contents of the +file or the new contents of the file (assuming that the filesystem +implements `rename(2)` atomically). + + +Calling sequence +---------------- + +The caller: + +* Allocates a `struct lock_file` either as a static variable or on the + heap, initialized to zeros. Once you use the structure to call the + `hold_lock_file_*` family of functions, it belongs to the lockfile + subsystem and its storage must remain valid throughout the life of + the program (i.e. you cannot use an on-stack variable to hold this + structure). + +* Attempts to create a lockfile by passing that variable and the path + of the final destination (e.g. `$GIT_DIR/index`) to + `hold_lock_file_for_update` or `hold_lock_file_for_append`. + +* Writes new content for the destination file by writing to the file + descriptor returned by those functions (also available via + `lock->fd`). + +When finished writing, the caller can: + +* Close the file descriptor and rename the lockfile to its final + destination by calling `commit_lock_file` or `commit_lock_file_to`. + +* Close the file descriptor and remove the lockfile by calling + `rollback_lock_file`. + +* Close the file descriptor without removing or renaming the lockfile + by calling `close_lock_file`, and later call `commit_lock_file`, + `commit_lock_file_to`, `rollback_lock_file`, or `reopen_lock_file`. + +Even after the lockfile is committed or rolled back, the `lock_file` +object must not be freed or altered by the caller. However, it may be +reused; just pass it to another call of `hold_lock_file_for_update` or +`hold_lock_file_for_append`. + +If the program exits before you have called one of `commit_lock_file`, +`commit_lock_file_to`, `rollback_lock_file`, or `close_lock_file`, an +`atexit(3)` handler will close and remove the lockfile, rolling back +any uncommitted changes. + +If you need to close the file descriptor you obtained from a +`hold_lock_file_*` function yourself, do so by calling +`close_lock_file`. You should never call `close(2)` yourself! +Otherwise the `struct lock_file` structure would still think that the +file descriptor needs to be closed, and a commit or rollback would +result in duplicate calls to `close(2)`. Worse yet, if you `close(2)` +and then later open another file descriptor for a completely different +purpose, then a commit or rollback might close that unrelated file +descriptor. + + +Error handling +-------------- + +The `hold_lock_file_*` functions return a file descriptor on success +or -1 on failure (unless `LOCK_DIE_ON_ERROR` is used; see below). On +errors, `errno` describes the reason for failure. Errors can be +reported by passing `errno` to one of the following helper functions: + +unable_to_lock_message:: + + Append an appropriate error message to a `strbuf`. + +unable_to_lock_error:: + + Emit an appropriate error message using `error()`. + +unable_to_lock_die:: + + Emit an appropriate error message and `die()`. + +Similarly, `commit_lock_file`, `commit_lock_file_to`, 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 +----- + +The following flags can be passed to `hold_lock_file_for_update` or +`hold_lock_file_for_append`: + +LOCK_NO_DEREF:: + + Usually symbolic links in the destination path are resolved + and the lockfile is created by adding ".lock" to the resolved + path. If `LOCK_NO_DEREF` is set, then the lockfile is created + by adding ".lock" to the path argument itself. This option is + used, for example, when locking a symbolic reference, which + for backwards-compatibility reasons can be a symbolic link + containing the name of the referred-to-reference. + +LOCK_DIE_ON_ERROR:: + + If a lock is already taken for the file, `die()` with an error + message. If this option is not specified, trying to lock a + file that is already locked returns -1 to the caller. The functions @@ -24,51 +132,77 @@ The functions hold_lock_file_for_update:: - Take a pointer to `struct lock_file`, the filename of - the final destination (e.g. `$GIT_DIR/index`) and a flag - `die_on_error`. Attempt to create a lockfile for the - destination and return the file descriptor for writing - to the file. If `die_on_error` flag is true, it dies if - a lock is already taken for the file; otherwise it - returns a negative integer to the caller on failure. + Take a pointer to `struct lock_file`, the path of the file to + be locked (e.g. `$GIT_DIR/index`) and a flags argument (see + above). Attempt to create a lockfile for the destination and + return the file descriptor for writing to the file. + +hold_lock_file_for_append:: + + Like `hold_lock_file_for_update`, but before returning copy + the existing contents of the file (if any) to the lockfile and + position its write pointer at the end of the file. + +get_locked_file_path:: + + Return the path of the file that is locked by the specified + lock_file object. The caller must free the memory. commit_lock_file:: - Take a pointer to the `struct lock_file` initialized - with an earlier call to `hold_lock_file_for_update()`, - close the file descriptor and rename the lockfile to its - final destination. Returns 0 upon success, a negative - value on failure to close(2) or rename(2). + 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 + rename the lockfile to its final destination. Return 0 upon + 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. + +commit_lock_file_to:: + + Like `commit_lock_file()`, except that it takes an explicit + `path` argument to which the lockfile should be renamed. The + `path` must be on the same filesystem as the lock file. rollback_lock_file:: - Take a pointer to the `struct lock_file` initialized - with an earlier call to `hold_lock_file_for_update()`, - close the file descriptor and remove the lockfile. + 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. 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:: - Take a pointer to the `struct lock_file` initialized - with an earlier call to `hold_lock_file_for_update()`, - and close the file descriptor. Returns 0 upon success, - a negative value on failure to close(2). - -Because the structure is used in an `atexit(3)` handler, its -storage has to stay throughout the life of the program. It -cannot be an auto variable allocated on the stack. - -Call `commit_lock_file()` or `rollback_lock_file()` when you are -done writing to the file descriptor. If you do not call either -and simply `exit(3)` from the program, an `atexit(3)` handler -will close and remove the lockfile. - -If you need to close the file descriptor you obtained from -`hold_lock_file_for_update` function yourself, do so by calling -`close_lock_file()`. You should never call `close(2)` yourself! -Otherwise the `struct -lock_file` structure still remembers that the file descriptor -needs to be closed, and a later call to `commit_lock_file()` or -`rollback_lock_file()` will result in duplicate calls to -`close(2)`. Worse yet, if you `close(2)`, open another file -descriptor for completely different purpose, and then call -`commit_lock_file()` or `rollback_lock_file()`, they may close -that unrelated file descriptor. + + 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`, and close the file descriptor. + Return 0 upon success. On failure to `close(2)`, return a + negative value and roll back the lock file. Usually + `commit_lock_file`, `commit_lock_file_to`, or + `rollback_lock_file` should eventually be called if + `close_lock_file` succeeds. + +reopen_lock_file:: + + Re-open a lockfile that has been closed (using + `close_lock_file`) but not yet committed or rolled back. This + can be used to implement a sequence of operations like the + following: + + * Lock file. + + * Write new contents to lockfile, then `close_lock_file` to + cause the contents to be written to disk. + + * Pass the name of the lockfile to another program to allow it + (and nobody else) to inspect the contents you wrote, while + still holding the lock yourself. + + * `reopen_lock_file` to reopen the lockfile. Make further + updates to the contents. + + * `commit_lock_file` to make the final version permanent. diff --git a/builtin/add.c b/builtin/add.c index 352b85e8db..ae6d3e262b 100644 --- a/builtin/add.c +++ b/builtin/add.c @@ -5,6 +5,7 @@ */ #include "cache.h" #include "builtin.h" +#include "lockfile.h" #include "dir.h" #include "pathspec.h" #include "exec_cmd.h" diff --git a/builtin/apply.c b/builtin/apply.c index 8714a88720..69efb0e4df 100644 --- a/builtin/apply.c +++ b/builtin/apply.c @@ -7,6 +7,7 @@ * */ #include "cache.h" +#include "lockfile.h" #include "cache-tree.h" #include "quote.h" #include "blob.h" diff --git a/builtin/checkout-index.c b/builtin/checkout-index.c index 05edd9e1df..383dccf93e 100644 --- a/builtin/checkout-index.c +++ b/builtin/checkout-index.c @@ -5,7 +5,7 @@ * */ #include "builtin.h" -#include "cache.h" +#include "lockfile.h" #include "quote.h" #include "cache-tree.h" #include "parse-options.h" diff --git a/builtin/checkout.c b/builtin/checkout.c index 8afdf2b5c4..570bb09c4f 100644 --- a/builtin/checkout.c +++ b/builtin/checkout.c @@ -1,5 +1,5 @@ -#include "cache.h" #include "builtin.h" +#include "lockfile.h" #include "parse-options.h" #include "refs.h" #include "commit.h" diff --git a/builtin/clone.c b/builtin/clone.c index 3927edfb6e..d3bf9532d6 100644 --- a/builtin/clone.c +++ b/builtin/clone.c @@ -9,6 +9,7 @@ */ #include "builtin.h" +#include "lockfile.h" #include "parse-options.h" #include "fetch-pack.h" #include "refs.h" diff --git a/builtin/commit.c b/builtin/commit.c index b0fe7847d3..c2300185ec 100644 --- a/builtin/commit.c +++ b/builtin/commit.c @@ -6,6 +6,7 @@ */ #include "cache.h" +#include "lockfile.h" #include "cache-tree.h" #include "color.h" #include "dir.h" @@ -315,8 +316,8 @@ static void refresh_cache_or_die(int refresh_flags) die_resolve_conflict("commit"); } -static char *prepare_index(int argc, const char **argv, const char *prefix, - const struct commit *current_head, int is_status) +static const char *prepare_index(int argc, const char **argv, const char *prefix, + const struct commit *current_head, int is_status) { struct string_list partial; struct pathspec pathspec; @@ -341,7 +342,7 @@ static char *prepare_index(int argc, const char **argv, const char *prefix, die(_("unable to create temporary index")); old_index_env = getenv(INDEX_ENVIRONMENT); - setenv(INDEX_ENVIRONMENT, index_lock.filename, 1); + setenv(INDEX_ENVIRONMENT, index_lock.filename.buf, 1); if (interactive_add(argc, argv, prefix, patch_interactive) != 0) die(_("interactive add failed")); @@ -352,7 +353,7 @@ static char *prepare_index(int argc, const char **argv, const char *prefix, unsetenv(INDEX_ENVIRONMENT); discard_cache(); - read_cache_from(index_lock.filename); + read_cache_from(index_lock.filename.buf); if (update_main_cache_tree(WRITE_TREE_SILENT) == 0) { if (reopen_lock_file(&index_lock) < 0) die(_("unable to write index file")); @@ -362,7 +363,7 @@ static char *prepare_index(int argc, const char **argv, const char *prefix, warning(_("Failed to update main cache tree")); commit_style = COMMIT_NORMAL; - return index_lock.filename; + return index_lock.filename.buf; } /* @@ -385,7 +386,7 @@ static char *prepare_index(int argc, const char **argv, const char *prefix, if (write_locked_index(&the_index, &index_lock, CLOSE_LOCK)) die(_("unable to write new_index file")); commit_style = COMMIT_NORMAL; - return index_lock.filename; + return index_lock.filename.buf; } /* @@ -472,9 +473,9 @@ static char *prepare_index(int argc, const char **argv, const char *prefix, die(_("unable to write temporary index file")); discard_cache(); - read_cache_from(false_lock.filename); + read_cache_from(false_lock.filename.buf); - return false_lock.filename; + return false_lock.filename.buf; } static int run_status(FILE *fp, const char *index_file, const char *prefix, int nowarn, diff --git a/builtin/describe.c b/builtin/describe.c index ee6a3b998f..9103193b4f 100644 --- a/builtin/describe.c +++ b/builtin/describe.c @@ -1,4 +1,5 @@ #include "cache.h" +#include "lockfile.h" #include "commit.h" #include "tag.h" #include "refs.h" diff --git a/builtin/diff.c b/builtin/diff.c index 0f247d2400..4326fa56bf 100644 --- a/builtin/diff.c +++ b/builtin/diff.c @@ -4,6 +4,7 @@ * Copyright (c) 2006 Junio C Hamano */ #include "cache.h" +#include "lockfile.h" #include "color.h" #include "commit.h" #include "blob.h" diff --git a/builtin/gc.c b/builtin/gc.c index ced1456e1e..005adbebea 100644 --- a/builtin/gc.c +++ b/builtin/gc.c @@ -11,7 +11,7 @@ */ #include "builtin.h" -#include "cache.h" +#include "lockfile.h" #include "parse-options.h" #include "run-command.h" #include "sigchain.h" diff --git a/builtin/merge.c b/builtin/merge.c index dff043dac3..4513fadc5f 100644 --- a/builtin/merge.c +++ b/builtin/merge.c @@ -9,6 +9,7 @@ #include "cache.h" #include "parse-options.h" #include "builtin.h" +#include "lockfile.h" #include "run-command.h" #include "diff.h" #include "refs.h" @@ -656,19 +657,18 @@ static int try_merge_strategy(const char *strategy, struct commit_list *common, struct commit_list *remoteheads, struct commit *head, const char *head_arg) { - struct lock_file *lock = xcalloc(1, sizeof(struct lock_file)); + static struct lock_file lock; - hold_locked_index(lock, 1); + hold_locked_index(&lock, 1); refresh_cache(REFRESH_QUIET); if (active_cache_changed && - write_locked_index(&the_index, lock, COMMIT_LOCK)) + write_locked_index(&the_index, &lock, COMMIT_LOCK)) return error(_("Unable to write index.")); - rollback_lock_file(lock); + rollback_lock_file(&lock); if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) { int clean, x; struct commit *result; - struct lock_file *lock = xcalloc(1, sizeof(struct lock_file)); struct commit_list *reversed = NULL; struct merge_options o; struct commit_list *j; @@ -696,13 +696,13 @@ static int try_merge_strategy(const char *strategy, struct commit_list *common, for (j = common; j; j = j->next) commit_list_insert(j->item, &reversed); - hold_locked_index(lock, 1); + hold_locked_index(&lock, 1); clean = merge_recursive(&o, head, remoteheads->item, reversed, &result); if (active_cache_changed && - write_locked_index(&the_index, lock, COMMIT_LOCK)) + write_locked_index(&the_index, &lock, COMMIT_LOCK)) die (_("unable to write %s"), get_index_file()); - rollback_lock_file(lock); + rollback_lock_file(&lock); return clean ? 0 : 1; } else { return try_merge_command(strategy, xopts_nr, xopts, diff --git a/builtin/mv.c b/builtin/mv.c index 8883baa903..563d05ba1a 100644 --- a/builtin/mv.c +++ b/builtin/mv.c @@ -3,8 +3,8 @@ * * Copyright (C) 2006 Johannes Schindelin */ -#include "cache.h" #include "builtin.h" +#include "lockfile.h" #include "dir.h" #include "cache-tree.h" #include "string-list.h" diff --git a/builtin/read-tree.c b/builtin/read-tree.c index e7e1c33a7f..43b47f72f1 100644 --- a/builtin/read-tree.c +++ b/builtin/read-tree.c @@ -5,6 +5,7 @@ */ #include "cache.h" +#include "lockfile.h" #include "object.h" #include "tree.h" #include "tree-walk.h" diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c index a01ac2096a..f2f6c67359 100644 --- a/builtin/receive-pack.c +++ b/builtin/receive-pack.c @@ -1,4 +1,5 @@ #include "builtin.h" +#include "lockfile.h" #include "pack.h" #include "refs.h" #include "pkt-line.h" diff --git a/builtin/reflog.c b/builtin/reflog.c index e8a8fb13b9..b6388f75b0 100644 --- a/builtin/reflog.c +++ b/builtin/reflog.c @@ -1,5 +1,5 @@ -#include "cache.h" #include "builtin.h" +#include "lockfile.h" #include "commit.h" #include "refs.h" #include "dir.h" @@ -431,7 +431,7 @@ static int expire_reflog(const char *ref, const unsigned char *sha1, int unused, write_str_in_full(lock->lock_fd, "\n") != 1 || close_ref(lock) < 0)) { status |= error("Couldn't write %s", - lock->lk->filename); + lock->lk->filename.buf); unlink(newlog_path); } else if (rename(newlog_path, log_file)) { status |= error("cannot rename %s to %s", diff --git a/builtin/reset.c b/builtin/reset.c index 855d478e3b..4c08ddc1ca 100644 --- a/builtin/reset.c +++ b/builtin/reset.c @@ -8,6 +8,7 @@ * Copyright (c) 2005, 2006 Linus Torvalds and Junio C Hamano */ #include "builtin.h" +#include "lockfile.h" #include "tag.h" #include "object.h" #include "commit.h" diff --git a/builtin/rm.c b/builtin/rm.c index 2b61d3bd41..d8a9c86dd1 100644 --- a/builtin/rm.c +++ b/builtin/rm.c @@ -3,8 +3,8 @@ * * Copyright (C) Linus Torvalds 2006 */ -#include "cache.h" #include "builtin.h" +#include "lockfile.h" #include "dir.h" #include "cache-tree.h" #include "tree-walk.h" diff --git a/builtin/update-index.c b/builtin/update-index.c index e8c7fd4d49..b0e3dc9105 100644 --- a/builtin/update-index.c +++ b/builtin/update-index.c @@ -4,6 +4,7 @@ * Copyright (C) Linus Torvalds, 2005 */ #include "cache.h" +#include "lockfile.h" #include "quote.h" #include "cache-tree.h" #include "tree-walk.h" @@ -942,7 +943,7 @@ int cmd_update_index(int argc, const char **argv, const char *prefix) if (newfd < 0) { if (refresh_args.flags & REFRESH_QUIET) exit(128); - unable_to_lock_index_die(get_index_file(), lock_error); + unable_to_lock_die(get_index_file(), lock_error); } if (write_locked_index(&the_index, lock_file, COMMIT_LOCK)) die("Unable to write new index file"); @@ -1,4 +1,5 @@ #include "cache.h" +#include "lockfile.h" #include "bundle.h" #include "object.h" #include "commit.h" diff --git a/cache-tree.c b/cache-tree.c index 75a54fdc72..215202c42d 100644 --- a/cache-tree.c +++ b/cache-tree.c @@ -1,4 +1,5 @@ #include "cache.h" +#include "lockfile.h" #include "tree.h" #include "tree-walk.h" #include "cache-tree.h" @@ -570,29 +570,11 @@ extern void fill_stat_cache_info(struct cache_entry *ce, struct stat *st); #define REFRESH_IN_PORCELAIN 0x0020 /* user friendly output, not "needs update" */ extern int refresh_index(struct index_state *, unsigned int flags, const struct pathspec *pathspec, char *seen, const char *header_msg); -struct lock_file { - struct lock_file *next; - int fd; - pid_t owner; - char on_list; - char filename[PATH_MAX]; -}; -#define LOCK_DIE_ON_ERROR 1 -#define LOCK_NODEREF 2 -extern int unable_to_lock_error(const char *path, int err); -extern void unable_to_lock_message(const char *path, int err, - struct strbuf *buf); -extern NORETURN void unable_to_lock_index_die(const char *path, int err); -extern int hold_lock_file_for_update(struct lock_file *, const char *path, int); -extern int hold_lock_file_for_append(struct lock_file *, const char *path, int); -extern int commit_lock_file(struct lock_file *); -extern int reopen_lock_file(struct lock_file *); extern void update_index_if_able(struct index_state *, struct lock_file *); extern int hold_locked_index(struct lock_file *, int); extern void set_alternate_index_output(const char *); -extern int close_lock_file(struct lock_file *); -extern void rollback_lock_file(struct lock_file *); + extern int delete_ref(const char *, const unsigned char *sha1, int delopt); /* Environment bits from configuration mechanism */ @@ -6,6 +6,7 @@ * */ #include "cache.h" +#include "lockfile.h" #include "exec_cmd.h" #include "strbuf.h" #include "quote.h" @@ -2040,9 +2041,9 @@ int git_config_set_multivar_in_file(const char *config_filename, MAP_PRIVATE, in_fd, 0); close(in_fd); - if (chmod(lock->filename, st.st_mode & 07777) < 0) { + if (chmod(lock->filename.buf, st.st_mode & 07777) < 0) { error("chmod on %s failed: %s", - lock->filename, strerror(errno)); + lock->filename.buf, strerror(errno)); ret = CONFIG_NO_WRITE; goto out_free; } @@ -2099,6 +2100,7 @@ int git_config_set_multivar_in_file(const char *config_filename, if (commit_lock_file(lock) < 0) { error("could not commit config file %s", config_filename); ret = CONFIG_NO_WRITE; + lock = NULL; goto out_free; } @@ -2121,7 +2123,7 @@ out_free: return ret; write_err_out: - ret = write_error(lock->filename); + ret = write_error(lock->filename.buf); goto out_free; } @@ -2222,9 +2224,9 @@ int git_config_rename_section_in_file(const char *config_filename, fstat(fileno(config_file), &st); - if (chmod(lock->filename, st.st_mode & 07777) < 0) { + if (chmod(lock->filename.buf, st.st_mode & 07777) < 0) { ret = error("chmod on %s failed: %s", - lock->filename, strerror(errno)); + lock->filename.buf, strerror(errno)); goto out; } @@ -2245,7 +2247,7 @@ int git_config_rename_section_in_file(const char *config_filename, } store.baselen = strlen(new_name); if (!store_write_section(out_fd, new_name)) { - ret = write_error(lock->filename); + ret = write_error(lock->filename.buf); goto out; } /* @@ -2271,7 +2273,7 @@ int git_config_rename_section_in_file(const char *config_filename, continue; length = strlen(output); if (write_in_full(out_fd, output, length) != length) { - ret = write_error(lock->filename); + ret = write_error(lock->filename.buf); goto out; } } diff --git a/credential-store.c b/credential-store.c index f9146e576f..d435514cbe 100644 --- a/credential-store.c +++ b/credential-store.c @@ -1,4 +1,5 @@ #include "cache.h" +#include "lockfile.h" #include "credential.h" #include "string-list.h" #include "parse-options.h" diff --git a/fast-import.c b/fast-import.c index 96b0f4236a..deadc33f94 100644 --- a/fast-import.c +++ b/fast-import.c @@ -153,6 +153,7 @@ Format of STDIN stream: #include "builtin.h" #include "cache.h" +#include "lockfile.h" #include "object.h" #include "blob.h" #include "tree.h" @@ -1832,10 +1833,8 @@ static void dump_marks(void) } if (commit_lock_file(&mark_lock)) { - int saved_errno = errno; - rollback_lock_file(&mark_lock); failure |= error("Unable to commit marks file %s: %s", - export_marks_file, strerror(saved_errno)); + export_marks_file, strerror(errno)); return; } } diff --git a/fetch-pack.c b/fetch-pack.c index 7487aa7306..655ee64256 100644 --- a/fetch-pack.c +++ b/fetch-pack.c @@ -1,4 +1,5 @@ #include "cache.h" +#include "lockfile.h" #include "refs.h" #include "pkt-line.h" #include "commit.h" diff --git a/lockfile.c b/lockfile.c index d34a96df4f..7bfec4b773 100644 --- a/lockfile.c +++ b/lockfile.c @@ -2,59 +2,52 @@ * Copyright (c) 2005, Junio C Hamano */ #include "cache.h" +#include "lockfile.h" #include "sigchain.h" -static struct lock_file *lock_file_list; +static struct lock_file *volatile lock_file_list; -static void remove_lock_file(void) +static void remove_lock_files(void) { pid_t me = getpid(); while (lock_file_list) { - if (lock_file_list->owner == me && - lock_file_list->filename[0]) { - if (lock_file_list->fd >= 0) - close(lock_file_list->fd); - unlink_or_warn(lock_file_list->filename); - } + if (lock_file_list->owner == me) + rollback_lock_file(lock_file_list); lock_file_list = lock_file_list->next; } } -static void remove_lock_file_on_signal(int signo) +static void remove_lock_files_on_signal(int signo) { - remove_lock_file(); + remove_lock_files(); sigchain_pop(signo); raise(signo); } /* - * p = absolute or relative path name + * path = absolute or relative path name * - * Return a pointer into p showing the beginning of the last path name - * element. If p is empty or the root directory ("/"), just return p. + * Remove the last path name element from path (leaving the preceding + * "/", if any). If path is empty or the root directory ("/"), set + * path to the empty string. */ -static char *last_path_elm(char *p) +static void trim_last_path_component(struct strbuf *path) { - /* r starts pointing to null at the end of the string */ - char *r = strchr(p, '\0'); - - if (r == p) - return p; /* just return empty string */ - - r--; /* back up to last non-null character */ + int i = path->len; /* back up past trailing slashes, if any */ - while (r > p && *r == '/') - r--; + while (i && path->buf[i - 1] == '/') + i--; /* - * then go backwards until I hit a slash, or the beginning of - * the string + * then go backwards until a slash, or the beginning of the + * string */ - while (r > p && *(r-1) != '/') - r--; - return r; + while (i && path->buf[i - 1] != '/') + i--; + + strbuf_setlen(path, i); } @@ -62,103 +55,87 @@ static char *last_path_elm(char *p) #define MAXDEPTH 5 /* - * p = path that may be a symlink - * s = full size of p - * - * If p is a symlink, attempt to overwrite p with a path to the real - * file or directory (which may or may not exist), following a chain of - * symlinks if necessary. Otherwise, leave p unmodified. + * path contains a path that might be a symlink. * - * This is a best-effort routine. If an error occurs, p will either be - * left unmodified or will name a different symlink in a symlink chain - * that started with p's initial contents. + * If path is a symlink, attempt to overwrite it with a path to the + * real file or directory (which may or may not exist), following a + * chain of symlinks if necessary. Otherwise, leave path unmodified. * - * Always returns p. + * This is a best-effort routine. If an error occurs, path will + * either be left unmodified or will name a different symlink in a + * symlink chain that started with the original path. */ - -static char *resolve_symlink(char *p, size_t s) +static void resolve_symlink(struct strbuf *path) { int depth = MAXDEPTH; + static struct strbuf link = STRBUF_INIT; while (depth--) { - char link[PATH_MAX]; - int link_len = readlink(p, link, sizeof(link)); - if (link_len < 0) { - /* not a symlink anymore */ - return p; - } - else if (link_len < sizeof(link)) - /* readlink() never null-terminates */ - link[link_len] = '\0'; - else { - warning("%s: symlink too long", p); - return p; - } + if (strbuf_readlink(&link, path->buf, path->len) < 0) + break; - if (is_absolute_path(link)) { + if (is_absolute_path(link.buf)) /* absolute path simply replaces p */ - if (link_len < s) - strcpy(p, link); - else { - warning("%s: symlink too long", p); - return p; - } - } else { + strbuf_reset(path); + else /* - * link is a relative path, so I must replace the + * link is a relative path, so replace the * last element of p with it. */ - char *r = (char *)last_path_elm(p); - if (r - p + link_len < s) - strcpy(r, link); - else { - warning("%s: symlink too long", p); - return p; - } - } + trim_last_path_component(path); + + strbuf_addbuf(path, &link); } - return p; + strbuf_reset(&link); } /* Make sure errno contains a meaningful value on error */ static int lock_file(struct lock_file *lk, const char *path, int flags) { - /* - * subtract 5 from size to make sure there's room for adding - * ".lock" for the lock file name - */ - static const size_t max_path_len = sizeof(lk->filename) - 5; + size_t pathlen = strlen(path); - if (strlen(path) >= max_path_len) { - errno = ENAMETOOLONG; + if (!lock_file_list) { + /* One-time initialization */ + sigchain_push_common(remove_lock_files_on_signal); + atexit(remove_lock_files); + } + + if (lk->active) + die("BUG: cannot lock_file(\"%s\") using active struct lock_file", + path); + if (!lk->on_list) { + /* Initialize *lk and add it to lock_file_list: */ + lk->fd = -1; + lk->active = 0; + lk->owner = 0; + strbuf_init(&lk->filename, pathlen + LOCK_SUFFIX_LEN); + lk->next = lock_file_list; + lock_file_list = lk; + lk->on_list = 1; + } else if (lk->filename.len) { + /* This shouldn't happen, but better safe than sorry. */ + die("BUG: lock_file(\"%s\") called with improperly-reset lock_file object", + path); + } + + strbuf_add(&lk->filename, path, pathlen); + if (!(flags & LOCK_NO_DEREF)) + resolve_symlink(&lk->filename); + strbuf_addstr(&lk->filename, LOCK_SUFFIX); + lk->fd = open(lk->filename.buf, O_RDWR | O_CREAT | O_EXCL, 0666); + if (lk->fd < 0) { + strbuf_reset(&lk->filename); return -1; } - strcpy(lk->filename, path); - if (!(flags & LOCK_NODEREF)) - resolve_symlink(lk->filename, max_path_len); - strcat(lk->filename, ".lock"); - lk->fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666); - if (0 <= lk->fd) { - if (!lock_file_list) { - sigchain_push_common(remove_lock_file_on_signal); - atexit(remove_lock_file); - } - lk->owner = getpid(); - if (!lk->on_list) { - lk->next = lock_file_list; - lock_file_list = lk; - lk->on_list = 1; - } - if (adjust_shared_perm(lk->filename)) { - int save_errno = errno; - error("cannot fix permission bits on %s", - lk->filename); - errno = save_errno; - return -1; - } + lk->owner = getpid(); + lk->active = 1; + if (adjust_shared_perm(lk->filename.buf)) { + int save_errno = errno; + error("cannot fix permission bits on %s", lk->filename.buf); + rollback_lock_file(lk); + errno = save_errno; + return -1; } - else - lk->filename[0] = 0; return lk->fd; } @@ -185,7 +162,7 @@ int unable_to_lock_error(const char *path, int err) return -1; } -NORETURN void unable_to_lock_index_die(const char *path, int err) +NORETURN void unable_to_lock_die(const char *path, int err) { struct strbuf buf = STRBUF_INIT; @@ -198,7 +175,7 @@ int hold_lock_file_for_update(struct lock_file *lk, const char *path, int flags) { int fd = lock_file(lk, path, flags); if (fd < 0 && (flags & LOCK_DIE_ON_ERROR)) - unable_to_lock_index_die(path, errno); + unable_to_lock_die(path, errno); return fd; } @@ -209,23 +186,30 @@ int hold_lock_file_for_append(struct lock_file *lk, const char *path, int flags) fd = lock_file(lk, path, flags); if (fd < 0) { if (flags & LOCK_DIE_ON_ERROR) - unable_to_lock_index_die(path, errno); + unable_to_lock_die(path, errno); return fd; } orig_fd = open(path, O_RDONLY); if (orig_fd < 0) { if (errno != ENOENT) { + int save_errno = errno; + if (flags & LOCK_DIE_ON_ERROR) die("cannot open '%s' for copying", path); - close(fd); - return error("cannot open '%s' for copying", path); + rollback_lock_file(lk); + error("cannot open '%s' for copying", path); + errno = save_errno; + return -1; } } else if (copy_fd(orig_fd, fd)) { + int save_errno = errno; + if (flags & LOCK_DIE_ON_ERROR) exit(128); close(orig_fd); - close(fd); + rollback_lock_file(lk); + errno = save_errno; return -1; } else { close(orig_fd); @@ -233,52 +217,90 @@ int hold_lock_file_for_append(struct lock_file *lk, const char *path, int flags) return fd; } +char *get_locked_file_path(struct lock_file *lk) +{ + if (!lk->active) + die("BUG: get_locked_file_path() called for unlocked object"); + if (lk->filename.len <= LOCK_SUFFIX_LEN) + die("BUG: get_locked_file_path() called for malformed lock object"); + return xmemdupz(lk->filename.buf, lk->filename.len - LOCK_SUFFIX_LEN); +} + int close_lock_file(struct lock_file *lk) { int fd = lk->fd; + + if (fd < 0) + return 0; + lk->fd = -1; - return close(fd); + if (close(fd)) { + int save_errno = errno; + rollback_lock_file(lk); + errno = save_errno; + return -1; + } + return 0; } int reopen_lock_file(struct lock_file *lk) { if (0 <= lk->fd) die(_("BUG: reopen a lockfile that is still open")); - if (!lk->filename[0]) + if (!lk->active) die(_("BUG: reopen a lockfile that has been committed")); - lk->fd = open(lk->filename, O_WRONLY); + lk->fd = open(lk->filename.buf, O_WRONLY); return lk->fd; } -int commit_lock_file(struct lock_file *lk) +int commit_lock_file_to(struct lock_file *lk, const char *path) { - char result_file[PATH_MAX]; - size_t i; - if (lk->fd >= 0 && close_lock_file(lk)) + if (!lk->active) + die("BUG: attempt to commit unlocked object to \"%s\"", path); + + if (close_lock_file(lk)) return -1; - strcpy(result_file, lk->filename); - i = strlen(result_file) - 5; /* .lock */ - result_file[i] = 0; - if (rename(lk->filename, result_file)) + + if (rename(lk->filename.buf, path)) { + int save_errno = errno; + rollback_lock_file(lk); + errno = save_errno; return -1; - lk->filename[0] = 0; + } + + lk->active = 0; + strbuf_reset(&lk->filename); return 0; } -int hold_locked_index(struct lock_file *lk, int die_on_error) +int commit_lock_file(struct lock_file *lk) { - return hold_lock_file_for_update(lk, get_index_file(), - die_on_error - ? LOCK_DIE_ON_ERROR - : 0); + static struct strbuf result_file = STRBUF_INIT; + int err; + + if (!lk->active) + die("BUG: attempt to commit unlocked object"); + + if (lk->filename.len <= LOCK_SUFFIX_LEN || + strcmp(lk->filename.buf + lk->filename.len - LOCK_SUFFIX_LEN, LOCK_SUFFIX)) + die("BUG: lockfile filename corrupt"); + + /* remove ".lock": */ + strbuf_add(&result_file, lk->filename.buf, + lk->filename.len - LOCK_SUFFIX_LEN); + err = commit_lock_file_to(lk, result_file.buf); + strbuf_reset(&result_file); + return err; } void rollback_lock_file(struct lock_file *lk) { - if (lk->filename[0]) { - if (lk->fd >= 0) - close(lk->fd); - unlink_or_warn(lk->filename); + if (!lk->active) + return; + + if (!close_lock_file(lk)) { + unlink_or_warn(lk->filename.buf); + lk->active = 0; + strbuf_reset(&lk->filename); } - lk->filename[0] = 0; } diff --git a/lockfile.h b/lockfile.h new file mode 100644 index 0000000000..9059e8958f --- /dev/null +++ b/lockfile.h @@ -0,0 +1,84 @@ +#ifndef LOCKFILE_H +#define LOCKFILE_H + +/* + * File write-locks as used by Git. + * + * For an overview of how to use the lockfile API, please see + * + * Documentation/technical/api-lockfile.txt + * + * This module keeps track of all locked files in lock_file_list for + * use at cleanup. This list and the lock_file objects that comprise + * it must be kept in self-consistent states at all time, because the + * program can be interrupted any time by a signal, in which case the + * signal handler will walk through the list attempting to clean up + * any open lock files. + * + * A lockfile is owned by the process that created it. The lock_file + * object has an "owner" field that records its owner. This field is + * used to prevent a forked process from closing a lockfile created by + * its parent. + * + * The possible states of a lock_file object are as follows: + * + * - Uninitialized. In this state the object's on_list field must be + * zero but the rest of its contents need not be initialized. As + * soon as the object is used in any way, it is irrevocably + * registered in the lock_file_list, and on_list is set. + * + * - Locked, lockfile open (after hold_lock_file_for_update(), + * hold_lock_file_for_append(), or reopen_lock_file()). In this + * state: + * - the lockfile exists + * - active is set + * - filename holds the filename of the lockfile + * - fd holds a file descriptor open for writing to the lockfile + * - owner holds the PID of the process that locked the file + * + * - Locked, lockfile closed (after successful close_lock_file()). + * Same as the previous state, except that the lockfile is closed + * and fd is -1. + * + * - Unlocked (after commit_lock_file(), commit_lock_file_to(), + * rollback_lock_file(), a failed attempt to lock, or a failed + * close_lock_file()). In this state: + * - active is unset + * - filename is empty (usually, though there are transitory + * states in which this condition doesn't hold). Client code should + * *not* rely on the filename being empty in this state. + * - fd is -1 + * - the object is left registered in the lock_file_list, and + * on_list is set. + */ + +struct lock_file { + struct lock_file *volatile next; + volatile sig_atomic_t active; + volatile int fd; + volatile pid_t owner; + char on_list; + struct strbuf filename; +}; + +/* String appended to a filename to derive the lockfile name: */ +#define LOCK_SUFFIX ".lock" +#define LOCK_SUFFIX_LEN 5 + +#define LOCK_DIE_ON_ERROR 1 +#define LOCK_NO_DEREF 2 + +extern int unable_to_lock_error(const char *path, int err); +extern void unable_to_lock_message(const char *path, int err, + struct strbuf *buf); +extern NORETURN void unable_to_lock_die(const char *path, int err); +extern int hold_lock_file_for_update(struct lock_file *, const char *path, int); +extern int hold_lock_file_for_append(struct lock_file *, const char *path, int); +extern char *get_locked_file_path(struct lock_file *); +extern int commit_lock_file_to(struct lock_file *, const char *path); +extern int commit_lock_file(struct lock_file *); +extern int reopen_lock_file(struct lock_file *); +extern int close_lock_file(struct lock_file *); +extern void rollback_lock_file(struct lock_file *); + +#endif /* LOCKFILE_H */ diff --git a/merge-recursive.c b/merge-recursive.c index 9fc71a2391..fdb7d0f10b 100644 --- a/merge-recursive.c +++ b/merge-recursive.c @@ -5,6 +5,7 @@ */ #include "cache.h" #include "advice.h" +#include "lockfile.h" #include "cache-tree.h" #include "commit.h" #include "blob.h" @@ -1,4 +1,5 @@ #include "cache.h" +#include "lockfile.h" #include "commit.h" #include "run-command.h" #include "resolve-undo.h" diff --git a/read-cache.c b/read-cache.c index 2fc1182f22..8f3e9eb314 100644 --- a/read-cache.c +++ b/read-cache.c @@ -5,6 +5,7 @@ */ #define NO_THE_INDEX_COMPATIBILITY_MACROS #include "cache.h" +#include "lockfile.h" #include "cache-tree.h" #include "refs.h" #include "dir.h" @@ -1367,6 +1368,14 @@ static int read_index_extension(struct index_state *istate, return 0; } +int hold_locked_index(struct lock_file *lk, int die_on_error) +{ + return hold_lock_file_for_update(lk, get_index_file(), + die_on_error + ? LOCK_DIE_ON_ERROR + : 0); +} + int read_index(struct index_state *istate) { return read_index_from(istate, get_index_file()); @@ -2041,16 +2050,10 @@ void set_alternate_index_output(const char *name) static int commit_locked_index(struct lock_file *lk) { - if (alternate_index_output) { - if (lk->fd >= 0 && close_lock_file(lk)) - return -1; - if (rename(lk->filename, alternate_index_output)) - return -1; - lk->filename[0] = 0; - return 0; - } else { + if (alternate_index_output) + return commit_lock_file_to(lk, alternate_index_output); + else return commit_lock_file(lk); - } } static int do_write_locked_index(struct index_state *istate, struct lock_file *lock, @@ -1,4 +1,5 @@ #include "cache.h" +#include "lockfile.h" #include "refs.h" #include "object.h" #include "tag.h" @@ -79,7 +80,8 @@ out: if (refname[1] == '\0') return -1; /* Component equals ".". */ } - if (cp - refname >= 5 && !memcmp(cp - 5, ".lock", 5)) + if (cp - refname >= LOCK_SUFFIX_LEN && + !memcmp(cp - LOCK_SUFFIX_LEN, LOCK_SUFFIX, LOCK_SUFFIX_LEN)) return -1; /* Refname ends with ".lock". */ return cp - refname; } @@ -2191,7 +2193,7 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname, lflags = 0; if (flags & REF_NODEREF) { refname = orig_refname; - lflags |= LOCK_NODEREF; + lflags |= LOCK_NO_DEREF; } lock->ref_name = xstrdup(refname); lock->orig_ref_name = xstrdup(orig_refname); @@ -2225,7 +2227,7 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname, */ goto retry; else - unable_to_lock_index_die(ref_file, errno); + unable_to_lock_die(ref_file, errno); } return old_sha1 ? verify_lock(lock, old_sha1, mustexist) : lock; @@ -2601,12 +2603,13 @@ int repack_without_refs(const char **refnames, int n, struct strbuf *err) static int delete_ref_loose(struct ref_lock *lock, int flag) { if (!(flag & REF_ISPACKED) || flag & REF_ISSYMREF) { - /* loose */ - int err, i = strlen(lock->lk->filename) - 5; /* .lock */ - - lock->lk->filename[i] = 0; - err = unlink_or_warn(lock->lk->filename); - lock->lk->filename[i] = '.'; + /* + * loose. The loose file name is the same as the + * lockfile name, minus ".lock": + */ + char *loose_filename = get_locked_file_path(lock->lk); + int err = unlink_or_warn(loose_filename); + free(loose_filename); if (err && errno != ENOENT) return 1; } @@ -2968,7 +2971,7 @@ int write_ref_sha1(struct ref_lock *lock, write_in_full(lock->lock_fd, &term, 1) != 1 || close_ref(lock) < 0) { int save_errno = errno; - error("Couldn't write %s", lock->lk->filename); + error("Couldn't write %s", lock->lk->filename.buf); unlock_ref(lock); errno = save_errno; return -1; @@ -1,4 +1,5 @@ #include "cache.h" +#include "lockfile.h" #include "string-list.h" #include "rerere.h" #include "xdiff-interface.h" diff --git a/sequencer.c b/sequencer.c index 5e8a207474..1b9a35e587 100644 --- a/sequencer.c +++ b/sequencer.c @@ -1,4 +1,5 @@ #include "cache.h" +#include "lockfile.h" #include "sequencer.h" #include "dir.h" #include "object.h" diff --git a/sha1_file.c b/sha1_file.c index 6f18c22ab1..83f77f01b6 100644 --- a/sha1_file.c +++ b/sha1_file.c @@ -8,6 +8,7 @@ */ #include "cache.h" #include "string-list.h" +#include "lockfile.h" #include "delta.h" #include "pack.h" #include "blob.h" @@ -1,4 +1,5 @@ #include "cache.h" +#include "lockfile.h" #include "commit.h" #include "tag.h" #include "pkt-line.h" @@ -269,8 +270,8 @@ void setup_alternate_shallow(struct lock_file *shallow_lock, if (write_shallow_commits(&sb, 0, extra)) { if (write_in_full(fd, sb.buf, sb.len) != sb.len) die_errno("failed to write to %s", - shallow_lock->filename); - *alternate_shallow_file = shallow_lock->filename; + shallow_lock->filename.buf); + *alternate_shallow_file = shallow_lock->filename.buf; } else /* * is_repository_shallow() sees empty string as "no @@ -316,7 +317,7 @@ void prune_shallow(int show_only) if (write_shallow_commits_1(&sb, 0, NULL, SEEN_ONLY)) { if (write_in_full(fd, sb.buf, sb.len) != sb.len) die_errno("failed to write to %s", - shallow_lock.filename); + shallow_lock.filename.buf); commit_lock_file(&shallow_lock); } else { unlink(git_path("shallow")); diff --git a/test-scrap-cache-tree.c b/test-scrap-cache-tree.c index 9ebcbca9d2..6efee31a48 100644 --- a/test-scrap-cache-tree.c +++ b/test-scrap-cache-tree.c @@ -1,4 +1,5 @@ #include "cache.h" +#include "lockfile.h" #include "tree.h" #include "cache-tree.h" |