Andy Whitcroft wrote:
> Junio C Hamano wrote:
>> Andy Whitcroft <apw@xxxxxxxxxxxx> writes:
>>
>>> We have an xread() wrapper to help us with those nasty
>>> interrupt returns and yet we fail to use it consistently.
>>> This patch updates those plain read()'s which do not
>>> have any handling for errors, or which treat those errors
>>> as user visible fatal errors.
>>>
>>> This feels right to me, but perhaps there is some good
>>> reason that things are done this way ... if so could
>>> someone elighten me.
>> Thanks.
>>
>> I do not think any of the changes you did introduced new bugs,
>> but I think some of them are still wrong. xread() protects us
>> from EINTR happening before any byte is read, but it can still
>> give a short read. Many callers have a loop like this:
>>
>> do {
>> size = xread(...);
>> yet_to_go -= size;
>> } while (yet_to_go);
>>
>> but some are not (e.g. add_excludes_from_file_1() in dir.c
>> expects xread() does not return before reading full buffer).
>
> Yes, that is true. I was going to fix that in the next step with the
> writes. But yes thats likely to involve them becoming 'read_in_full'
> style thing and in fact churn us more.
>
> Ignore this one and I'll look to do it 'right'.
Ok, after much hacking about I think I've got something sensible sorted
out for this. Following this email are four patches which convert the
various read/write/xread/xwrite users over to xread/read_in_full and
xwrite/write_in_full as appropriate. Its pretty invasive as obviously
I/O is pretty common in an SCM.
next with this stack passes the builtin test suite. I additionally used
the attached patch to induce severe short read/write semantics. Before
this patch series git was _very_ unhappy, unable to even create a
repository.
This series is against next.
-apw
diff --git a/git-compat-util.h b/git-compat-util.h
index 55456da..931cbed 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -210,6 +210,7 @@ static inline void *xmmap(void *start, size_t length,
static inline ssize_t xread(int fd, void *buf, size_t len)
{
ssize_t nr;
+ if (len > 5) len = 5;
while (1) {
nr = read(fd, buf, len);
if ((nr < 0) && (errno == EAGAIN || errno == EINTR))
@@ -221,6 +222,7 @@ static inline ssize_t xread(int fd, void *buf, size_t len)
static inline ssize_t xwrite(int fd, const void *buf, size_t len)
{
ssize_t nr;
+ if (len > 5) len = 5;
while (1) {
nr = write(fd, buf, len);
if ((nr < 0) && (errno == EAGAIN || errno == EINTR))