Re: [PATCH v8 1/2] Add xpread()
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Apr 10, 2014, 19:20 UTC
- Message-ID
- <xmqqtxa1vvms.fsf@gitster.dls.corp.google.com>
- In-Reply-To
- <5346ED16.3050607@kdbg.org>
Johannes Sixt <j6t@kdbg.org> writes:
Show 10 quoted lines
> Am 10.04.2014 20:54, schrieb Yiannis Marangos:
>> +ssize_t xpread(int fd, void *buf, size_t len, off_t offset)
>> +{
>> + ssize_t nr;
>> + if (len > MAX_IO_SIZE)
>> + len = MAX_IO_SIZE;
>
> Odd indentation here.
>
> -- HannesGood eyes, even though this is copy&pasting an existing error from surrounding code ;-)
I'll queue this instead (rebased on top of maint-1.8.5 even though I doubt we would be issuing 1.8.5.6).
-- >8 -- From: Yiannis Marangos <yiannis.marangos@gmail.com> Date: Thu, 10 Apr 2014 21:54:12 +0300 Subject: [PATCH] wrapper.c: add xpread() similar to xread()
It is a common mistake to call read(2)/pread(2) and forget to anticipate that they may return error with EAGAIN/EINTR when the system call is interrupted.
We have xread() helper to relieve callers of read(2) from having to worry about it; add xpread() helper to do the same for pread(2).
Update the caller in the builtin/index-pack.c and the mmap emulation in compat/.
Signed-off-by: Yiannis Marangos <yiannis.marangos@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> --- builtin/index-pack.c | 2 +- compat/mmap.c | 4 +--- git-compat-util.h | 1 + wrapper.c | 18 ++++++++++++++++++ 4 files changed, 21 insertions(+), 4 deletions(-)
diff --git a/builtin/index-pack.c b/builtin/index-pack.c index 9e9eb4b..e7a6b53 100644 --- a/builtin/index-pack.c +++ b/builtin/index-pack.c @@ -542,7 +542,7 @@ static void *unpack_data(struct object_entry *obj, do { ssize_t n = (len < 64*1024) ? len : 64*1024; - n = pread(pack_fd, inbuf, n, from); + n = xpread(pack_fd, inbuf, n, from); if (n < 0) die_errno(_("cannot pread pack file")); if (!n) diff --git a/compat/mmap.c b/compat/mmap.c index c9d46d1..7f662fe 100644 --- a/compat/mmap.c +++ b/compat/mmap.c @@ -14,7 +14,7 @@ void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t of } while (n < length) { - ssize_t count = pread(fd, (char *)start + n, length - n, offset + n); + ssize_t count = xpread(fd, (char *)start + n, length - n, offset + n); if (count == 0) { memset((char *)start+n, 0, length-n); @@ -22,8 +22,6 @@ void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t of } if (count < 0) { - if (errno == EAGAIN || errno == EINTR) - continue; free(start); errno = EACCES; return MAP_FAILED; diff --git a/git-compat-util.h b/git-compat-util.h index 7776f12..9eec5fb 100644 --- a/git-compat-util.h +++ b/git-compat-util.h @@ -534,6 +534,7 @@ extern void *xcalloc(size_t nmemb, size_t size); extern void *xmmap(void *start, size_t length, int prot, int flags, int fd, off_t offset); extern ssize_t xread(int fd, void *buf, size_t len); extern ssize_t xwrite(int fd, const void *buf, size_t len); +extern ssize_t xpread(int fd, void *buf, size_t len, off_t offset); extern int xdup(int fd); extern FILE *xfdopen(int fd, const char *mode); extern int xmkstemp(char *template); diff --git a/wrapper.c b/wrapper.c index 0cc5636..5b3c7fc 100644 --- a/wrapper.c +++ b/wrapper.c @@ -174,6 +174,24 @@ ssize_t xwrite(int fd, const void *buf, size_t len) } } +/* + * xpread() is the same as pread(), but it automatically restarts pread() + * operations with a recoverable error (EAGAIN and EINTR). xpread() DOES + * NOT GUARANTEE that "len" bytes is read even if the data is available. + */ +ssize_t xpread(int fd, void *buf, size_t len, off_t offset) +{ + ssize_t nr; + if (len > MAX_IO_SIZE) + len = MAX_IO_SIZE; + while (1) { + nr = pread(fd, buf, len, offset); + if ((nr < 0) && (errno == EAGAIN || errno == EINTR)) + continue; + return nr; + } +} + ssize_t read_in_full(int fd, void *buf, size_t count) { char *p = buf;
-- 1.9.2-590-g468068b