* [PATCH 2/8] Add a lockfile function to append to a file
@ 2008-04-17 23:32 Daniel Barkalow
2008-04-17 23:41 ` Junio C Hamano
2008-04-17 23:51 ` Junio C Hamano
0 siblings, 2 replies; 7+ messages in thread
From: Daniel Barkalow @ 2008-04-17 23:32 UTC (permalink / raw)
To: Junio C Hamano; +Cc: git, Johannes Schindelin
This takes care of copying the original contents into the replacement
file after the lock is held, so that concurrent additions can't miss
each other's changes.
Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>
---
cache.h | 1 +
lockfile.c | 17 +++++++++++++++++
2 files changed, 18 insertions(+), 0 deletions(-)
diff --git a/cache.h b/cache.h
index 2a1e7ec..4a113b0 100644
--- a/cache.h
+++ b/cache.h
@@ -391,6 +391,7 @@ struct lock_file {
char filename[PATH_MAX];
};
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 hold_locked_index(struct lock_file *, int);
diff --git a/lockfile.c b/lockfile.c
index 663f18f..95fd3d1 100644
--- a/lockfile.c
+++ b/lockfile.c
@@ -160,6 +160,23 @@ int hold_lock_file_for_update(struct lock_file *lk, const char *path, int die_on
return fd;
}
+int hold_lock_file_for_append(struct lock_file *lk, const char *path, int die_on_error)
+{
+ int fd = lock_file(lk, path);
+ struct stat st;
+ if (!stat(path, &st)) {
+ int orig_fd = open(path, O_RDONLY);
+ size_t mmap_size = xsize_t(st.st_size);
+ void *mmap = xmmap(NULL, mmap_size, PROT_READ, MAP_PRIVATE,
+ orig_fd, 0);
+ write_or_die(fd, mmap, mmap_size);
+ munmap(mmap, mmap_size);
+ }
+ if (fd < 0 && die_on_error)
+ die("unable to create '%s.lock': %s", path, strerror(errno));
+ return fd;
+}
+
int close_lock_file(struct lock_file *lk)
{
int fd = lk->fd;
--
1.5.4.3.610.gea6cd
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH 2/8] Add a lockfile function to append to a file
2008-04-17 23:32 Daniel Barkalow
@ 2008-04-17 23:41 ` Junio C Hamano
2008-04-17 23:51 ` Junio C Hamano
1 sibling, 0 replies; 7+ messages in thread
From: Junio C Hamano @ 2008-04-17 23:41 UTC (permalink / raw)
To: Daniel Barkalow; +Cc: git, Johannes Schindelin
Daniel Barkalow <barkalow@iabervon.org> writes:
> This takes care of copying the original contents into the replacement
> file after the lock is held, so that concurrent additions can't miss
> each other's changes.
>
> Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>
> ---
> cache.h | 1 +
> lockfile.c | 17 +++++++++++++++++
> 2 files changed, 18 insertions(+), 0 deletions(-)
>
> diff --git a/cache.h b/cache.h
> index 2a1e7ec..4a113b0 100644
> --- a/cache.h
> +++ b/cache.h
> @@ -391,6 +391,7 @@ struct lock_file {
> char filename[PATH_MAX];
> };
> 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 hold_locked_index(struct lock_file *, int);
> diff --git a/lockfile.c b/lockfile.c
> index 663f18f..95fd3d1 100644
> --- a/lockfile.c
> +++ b/lockfile.c
> @@ -160,6 +160,23 @@ int hold_lock_file_for_update(struct lock_file *lk, const char *path, int die_on
> return fd;
> }
>
> +int hold_lock_file_for_append(struct lock_file *lk, const char *path, int die_on_error)
> +{
> + int fd = lock_file(lk, path);
> + struct stat st;
> + if (!stat(path, &st)) {
> + int orig_fd = open(path, O_RDONLY);
> + size_t mmap_size = xsize_t(st.st_size);
> + void *mmap = xmmap(NULL, mmap_size, PROT_READ, MAP_PRIVATE,
> + orig_fd, 0);
> + write_or_die(fd, mmap, mmap_size);
> + munmap(mmap, mmap_size);
> + }
> + if (fd < 0 && die_on_error)
> + die("unable to create '%s.lock': %s", path, strerror(errno));
Copying and checking are the other way around, aren't they? Grab the
lock, error out if you cannot, then read and copy.
> + return fd;
> +}
> +
> int close_lock_file(struct lock_file *lk)
> {
> int fd = lk->fd;
> --
> 1.5.4.3.610.gea6cd
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 2/8] Add a lockfile function to append to a file
2008-04-17 23:32 Daniel Barkalow
2008-04-17 23:41 ` Junio C Hamano
@ 2008-04-17 23:51 ` Junio C Hamano
1 sibling, 0 replies; 7+ messages in thread
From: Junio C Hamano @ 2008-04-17 23:51 UTC (permalink / raw)
To: Daniel Barkalow; +Cc: git, Johannes Schindelin
Daniel Barkalow <barkalow@iabervon.org> writes:
> +int hold_lock_file_for_append(struct lock_file *lk, const char *path, int die_on_error)
> +{
> + int fd = lock_file(lk, path);
> + struct stat st;
> + if (!stat(path, &st)) {
> + int orig_fd = open(path, O_RDONLY);
> + size_t mmap_size = xsize_t(st.st_size);
> + void *mmap = xmmap(NULL, mmap_size, PROT_READ, MAP_PRIVATE,
> + orig_fd, 0);
> + write_or_die(fd, mmap, mmap_size);
> + munmap(mmap, mmap_size);
> + }
> + if (fd < 0 && die_on_error)
> + die("unable to create '%s.lock': %s", path, strerror(errno));
> + return fd;
> +}
Another glitch. What should we do when stat(path) fails but the file
cannot be read?
I think the sequence actually should be:
fd = lock_file();
if (fd < 0)
error out;
orig_fd = open(path, O_RDONLY);
if (orig_fd < 0) {
if (errno != ENOENT)
die("unable to open %s", path);
copy;
}
return fd;
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH 2/8] Add a lockfile function to append to a file
@ 2008-04-18 0:02 Daniel Barkalow
2008-04-20 4:59 ` Junio C Hamano
0 siblings, 1 reply; 7+ messages in thread
From: Daniel Barkalow @ 2008-04-18 0:02 UTC (permalink / raw)
To: Junio C Hamano; +Cc: git, Johannes Schindelin
This takes care of copying the original contents into the replacement
file after the lock is held, so that concurrent additions can't miss
each other's changes.
Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>
---
How about this? Also doesn't leak a fd and catches trying to append to a
file you can't read. Should I worry about mmap failing after the open?
cache.h | 1 +
lockfile.c | 23 +++++++++++++++++++++++
2 files changed, 24 insertions(+), 0 deletions(-)
diff --git a/cache.h b/cache.h
index 50b28fa..8d066bf 100644
--- a/cache.h
+++ b/cache.h
@@ -391,6 +391,7 @@ struct lock_file {
char filename[PATH_MAX];
};
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 hold_locked_index(struct lock_file *, int);
diff --git a/lockfile.c b/lockfile.c
index 663f18f..f1b5416 100644
--- a/lockfile.c
+++ b/lockfile.c
@@ -160,6 +160,29 @@ int hold_lock_file_for_update(struct lock_file *lk, const char *path, int die_on
return fd;
}
+int hold_lock_file_for_append(struct lock_file *lk, const char *path, int die_on_error)
+{
+ int fd = lock_file(lk, path);
+ struct stat st;
+ if (fd < 0) {
+ if (die_on_error)
+ die("unable to create '%s.lock': %s",
+ path, strerror(errno));
+ } else if (!stat(path, &st)) {
+ int orig_fd = open(path, O_RDONLY);
+ size_t mmap_size = xsize_t(st.st_size);
+ void *mmap;
+ if (orig_fd < 0)
+ die("unable to read %s to append to it", path);
+ mmap = xmmap(NULL, mmap_size, PROT_READ, MAP_PRIVATE,
+ orig_fd, 0);
+ write_or_die(fd, mmap, mmap_size);
+ munmap(mmap, mmap_size);
+ close(orig_fd);
+ }
+ return fd;
+}
+
int close_lock_file(struct lock_file *lk)
{
int fd = lk->fd;
--
1.5.4.3.610.gea6cd
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH 2/8] Add a lockfile function to append to a file
2008-04-18 0:02 [PATCH 2/8] Add a lockfile function to append to a file Daniel Barkalow
@ 2008-04-20 4:59 ` Junio C Hamano
2008-04-20 16:14 ` Johannes Schindelin
2008-04-20 19:43 ` Daniel Barkalow
0 siblings, 2 replies; 7+ messages in thread
From: Junio C Hamano @ 2008-04-20 4:59 UTC (permalink / raw)
To: Daniel Barkalow; +Cc: git, Johannes Schindelin
Daniel Barkalow <barkalow@iabervon.org> writes:
> This takes care of copying the original contents into the replacement
> file after the lock is held, so that concurrent additions can't miss
> each other's changes.
>
> Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>
> ---
> How about this? Also doesn't leak a fd and catches trying to append to a
> file you can't read. Should I worry about mmap failing after the open?
We have copy.c to copy small existing files, while detecting failure to
copy properly. How about doing something like this instead?
cache.h | 1 +
lockfile.c | 28 ++++++++++++++++++++++++++++
2 files changed, 29 insertions(+), 0 deletions(-)
diff --git a/cache.h b/cache.h
index 50b28fa..8d066bf 100644
--- a/cache.h
+++ b/cache.h
@@ -391,6 +391,7 @@ struct lock_file {
char filename[PATH_MAX];
};
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 hold_locked_index(struct lock_file *, int);
diff --git a/lockfile.c b/lockfile.c
index 663f18f..e9e0095 100644
--- a/lockfile.c
+++ b/lockfile.c
@@ -160,6 +160,34 @@ int hold_lock_file_for_update(struct lock_file *lk, const char *path, int die_on
return fd;
}
+int hold_lock_file_for_append(struct lock_file *lk, const char *path, int die_on_error)
+{
+ int fd, orig_fd;
+
+ fd = lock_file(lk, path);
+ if (fd < 0) {
+ if (die_on_error)
+ die("unable to create '%s.lock': %s", path, strerror(errno));
+ return fd;
+ }
+
+ orig_fd = open(path, O_RDONLY);
+ if (orig_fd < 0) {
+ if (errno != ENOENT) {
+ if (die_on_error)
+ die("cannot open '%s' for copying", path);
+ close(fd);
+ return error("cannot open '%s' for copying", path);
+ }
+ } else if (copy_fd(orig_fd, fd)) {
+ if (die_on_error)
+ exit(128);
+ close(fd);
+ return -1;
+ }
+ return fd;
+}
+
int close_lock_file(struct lock_file *lk)
{
int fd = lk->fd;
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH 2/8] Add a lockfile function to append to a file
2008-04-20 4:59 ` Junio C Hamano
@ 2008-04-20 16:14 ` Johannes Schindelin
2008-04-20 19:43 ` Daniel Barkalow
1 sibling, 0 replies; 7+ messages in thread
From: Johannes Schindelin @ 2008-04-20 16:14 UTC (permalink / raw)
To: Junio C Hamano; +Cc: Daniel Barkalow, git
Hi,
On Sat, 19 Apr 2008, Junio C Hamano wrote:
> Daniel Barkalow <barkalow@iabervon.org> writes:
>
> > This takes care of copying the original contents into the replacement
> > file after the lock is held, so that concurrent additions can't miss
> > each other's changes.
> >
> > Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>
> > ---
> > How about this? Also doesn't leak a fd and catches trying to append to a
> > file you can't read. Should I worry about mmap failing after the open?
>
> We have copy.c to copy small existing files, while detecting failure to
> copy properly. How about doing something like this instead?
I like it.
Ciao,
Dscho
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 2/8] Add a lockfile function to append to a file
2008-04-20 4:59 ` Junio C Hamano
2008-04-20 16:14 ` Johannes Schindelin
@ 2008-04-20 19:43 ` Daniel Barkalow
1 sibling, 0 replies; 7+ messages in thread
From: Daniel Barkalow @ 2008-04-20 19:43 UTC (permalink / raw)
To: Junio C Hamano; +Cc: git, Johannes Schindelin
On Sat, 19 Apr 2008, Junio C Hamano wrote:
> Daniel Barkalow <barkalow@iabervon.org> writes:
>
> > This takes care of copying the original contents into the replacement
> > file after the lock is held, so that concurrent additions can't miss
> > each other's changes.
> >
> > Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>
> > ---
> > How about this? Also doesn't leak a fd and catches trying to append to a
> > file you can't read. Should I worry about mmap failing after the open?
>
> We have copy.c to copy small existing files, while detecting failure to
> copy properly. How about doing something like this instead?
Yeah, that's obviously the right thing to use.
-Daniel
*This .sig left intentionally blank*
^ permalink raw reply [flat|nested] 7+ messages in thread
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Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
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2008-04-18 0:02 [PATCH 2/8] Add a lockfile function to append to a file Daniel Barkalow
2008-04-20 4:59 ` Junio C Hamano
2008-04-20 16:14 ` Johannes Schindelin
2008-04-20 19:43 ` Daniel Barkalow
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2008-04-17 23:32 Daniel Barkalow
2008-04-17 23:41 ` Junio C Hamano
2008-04-17 23:51 ` Junio C Hamano
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