fix pread()'s short read in index-pack

Since v1.6.0.2~13^2~ the completion of a thin pack uses sha1write() for
its ability to compute a SHA1 on the written data.  This also provides
data buffering which, along with commit 92392b4a45, will confuse pread()
whenever an appended object is 1) freed due to memory pressure because
of the depth-first delta processing, and 2) needed again because it has
many delta children, and 3) its data is still buffered by sha1write().

Let's fix the issue by simply forcing cached data out when such an
object is written so it can be pread()'d at leisure.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

diff --git a/csum-file.c b/csum-file.c
index 28389541a32454f2d988bb02e4268ffe12755bbc..cfc1ac42b9fc9489237cd0bcd1652fb4df243512 100644 (file)
--- a/csum-file.c
+++ b/csum-file.c
@@ -11,7 +11,7 @@
 #include "progress.h"
 #include "csum-file.h"
 
-static void sha1flush(struct sha1file *f, unsigned int count)
+static void flush(struct sha1file *f, unsigned int count)
 {
        void *buf = f->buffer;
 
@@ -32,22 +32,28 @@ static void sha1flush(struct sha1file *f, unsigned int count)
        }
 }
 
-int sha1close(struct sha1file *f, unsigned char *result, unsigned int flags)
+void sha1flush(struct sha1file *f)
 {
-       int fd;
        unsigned offset = f->offset;
 
        if (offset) {
                SHA1_Update(&f->ctx, f->buffer, offset);
-               sha1flush(f, offset);
+               flush(f, offset);
                f->offset = 0;
        }
+}
+
+int sha1close(struct sha1file *f, unsigned char *result, unsigned int flags)
+{
+       int fd;
+
+       sha1flush(f);
        SHA1_Final(f->buffer, &f->ctx);
        if (result)
                hashcpy(result, f->buffer);
        if (flags & (CSUM_CLOSE | CSUM_FSYNC)) {
                /* write checksum and close fd */
-               sha1flush(f, 20);
+               flush(f, 20);
                if (flags & CSUM_FSYNC)
                        fsync_or_die(f->fd, f->name);
                if (close(f->fd))
@@ -76,7 +82,7 @@ int sha1write(struct sha1file *f, void *buf, unsigned int count)
                left -= nr;
                if (!left) {
                        SHA1_Update(&f->ctx, f->buffer, offset);
-                       sha1flush(f, offset);
+                       flush(f, offset);
                        offset = 0;
                }
                f->offset = offset;

diff --git a/csum-file.h b/csum-file.h
index 72c9487f4fd9fcab5e02fc2dc6afd3cb7f9c036a..01f13b550118769ed7fbe35fce9bd8c91d87e42d 100644 (file)
--- a/csum-file.h
+++ b/csum-file.h
@@ -24,6 +24,7 @@ extern struct sha1file *sha1fd(int fd, const char *name);
 extern struct sha1file *sha1fd_throughput(int fd, const char *name, struct progress *tp);
 extern int sha1close(struct sha1file *, unsigned char *, unsigned int);
 extern int sha1write(struct sha1file *, void *, unsigned int);
+extern void sha1flush(struct sha1file *f);
 extern void crc32_begin(struct sha1file *);
 extern uint32_t crc32_end(struct sha1file *);
 

diff --git a/index-pack.c b/index-pack.c
index c45ae20e8ffacefa43c5d0ab9daf0ff6ef181d4a..2a366206a4e830d0bb66d6ac708cd512a94d6d37 100644 (file)
--- a/index-pack.c
+++ b/index-pack.c
@@ -707,6 +707,7 @@ static struct object_entry *append_obj_to_pack(struct sha1file *f,
        obj[1].idx.offset = obj[0].idx.offset + n;
        obj[1].idx.offset += write_compressed(f, buf, size);
        obj[0].idx.crc32 = crc32_end(f);
+       sha1flush(f);
        hashcpy(obj->idx.sha1, sha1);
        return obj;
 }