From: Junio C Hamano <gitster@pobox•com>
To: Johannes Sixt <j6t@kdbg•org>
Cc: Yiannis Marangos <yiannis.marangos@gmail•com>, git@vger•kernel.org
Subject: Re: [PATCH v8 1/2] Add xpread()
Date: Thu, 10 Apr 2014 12:20:59 -0700 [thread overview]
Message-ID: <xmqqtxa1vvms.fsf@gitster.dls.corp.google.com> (raw)
In-Reply-To: <5346ED16.3050607@kdbg.org> (Johannes Sixt's message of "Thu, 10 Apr 2014 21:12:22 +0200")
Johannes Sixt <j6t@kdbg•org> writes:
> 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.
>
> -- Hannes
Good 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
prev parent reply other threads:[~2014-04-10 19:21 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-09 22:06 [PATCH] Verify index file before we opportunistically update it Yiannis Marangos
2014-04-09 22:06 ` Yiannis Marangos
2014-04-09 22:34 ` [PATCH v2] " Yiannis Marangos
2014-04-09 23:05 ` Junio C Hamano
2014-04-09 22:52 ` [PATCH v3] " Yiannis Marangos
2014-04-10 5:22 ` [PATCH v4] " Yiannis Marangos
2014-04-10 5:34 ` [PATCH v5] " Yiannis Marangos
2014-04-10 10:40 ` Duy Nguyen
2014-04-10 11:57 ` Yiannis Marangos
2014-04-10 16:57 ` Junio C Hamano
2014-04-10 13:11 ` [PATCH v6] " Yiannis Marangos
2014-04-10 18:31 ` [PATCH v7 1/2] Add xpread() and xpwrite() Yiannis Marangos
2014-04-10 18:31 ` [PATCH v7 2/2] Verify index file before we opportunistically update it Yiannis Marangos
2014-04-10 19:28 ` Junio C Hamano
2014-04-11 2:57 ` Duy Nguyen
2014-04-11 19:24 ` Junio C Hamano
2014-04-11 20:43 ` Junio C Hamano
2014-04-11 23:30 ` Yiannis Marangos
2014-04-12 0:10 ` Duy Nguyen
2014-04-12 4:19 ` Junio C Hamano
2014-04-12 7:05 ` Junio C Hamano
2014-04-12 10:13 ` Duy Nguyen
2014-04-14 18:50 ` Junio C Hamano
2014-04-11 7:47 ` Torsten Bögershausen
2014-04-11 15:58 ` Yiannis Marangos
2014-04-11 10:36 ` Duy Nguyen
2014-04-10 18:35 ` [PATCH v7 1/2] Add xpread() and xpwrite() Junio C Hamano
2014-04-10 18:44 ` Yiannis Marangos
2014-04-10 18:54 ` [PATCH v8 1/2] Add xpread() Yiannis Marangos
2014-04-10 19:12 ` Johannes Sixt
2014-04-10 19:20 ` Junio C Hamano [this message]
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