[libvirt] [RFC PATCH 3/4] block: Enable QEMU to retrieve passed fd before attempting open
Corey Bryant
coreyb at linux.vnet.ibm.com
Mon May 21 20:19:57 UTC 2012
With this patch, when QEMU needs to "open" a file, it will first
check to see if a matching filename/fd pair were passed via the
-filefd command line option or the getfd_file monitor command.
If a match is found, QEMU will use the passed fd and will not
attempt to open the file. Otherwise, if a match is not found,
QEMU will attempt to open the file on it's own.
Signed-off-by: Corey Bryant <coreyb at linux.vnet.ibm.com>
---
block.c | 31 +++++++++++++++++++++++++++++++
block/raw-posix.c | 20 ++++++++++----------
block/raw-win32.c | 4 ++--
block/vdi.c | 4 ++--
block/vmdk.c | 21 +++++++++------------
block/vpc.c | 2 +-
block/vvfat.c | 4 ++--
block_int.h | 12 ++++++++++++
vl.c | 6 ++++++
9 files changed, 75 insertions(+), 29 deletions(-)
diff --git a/block.c b/block.c
index af2ab4f..6472114 100644
--- a/block.c
+++ b/block.c
@@ -102,6 +102,37 @@ static BlockDriverState *bs_snapshots;
/* If non-zero, use only whitelisted block drivers */
static int use_bdrv_whitelist;
+static int filename_match(QemuOpts *opts, void *opaque)
+{
+ const char *file = qemu_opt_get(opts, "file");
+ int fd = qemu_opt_get_number(opts, "fd", -1);
+
+ return (strcmp((char *)opaque, file) == 0) ? fd : 0;
+}
+
+int file_open(const char *filename, int flags, mode_t mode)
+{
+ int fd;
+
+#ifdef _WIN32
+ return qemu_open(filename, flags, mode);
+#else
+
+ fd = qemu_opts_foreach(qemu_find_opts("filefd"), filename_match,
+ (void *)filename, 1);
+ if (fd != 0) {
+ return dup(fd);
+ }
+
+ fd = qemu_get_fd_file(filename, false);
+ if (fd != -1) {
+ return dup(fd);
+ }
+
+ return qemu_open(filename, flags, mode);
+#endif
+}
+
#ifdef _WIN32
static int is_windows_drive_prefix(const char *filename)
{
diff --git a/block/raw-posix.c b/block/raw-posix.c
index 03fcfcc..4f7b40f 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -208,7 +208,7 @@ static int raw_open_common(BlockDriverState *bs, const char *filename,
s->open_flags |= O_DSYNC;
s->fd = -1;
- fd = qemu_open(filename, s->open_flags, 0644);
+ fd = file_open(filename, s->open_flags, 0644);
if (fd < 0) {
ret = -errno;
if (ret == -EROFS)
@@ -568,8 +568,8 @@ static int raw_create(const char *filename, QEMUOptionParameter *options)
options++;
}
- fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY,
- 0644);
+ fd = file_open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY,
+ 0644);
if (fd < 0) {
result = -errno;
} else {
@@ -741,7 +741,7 @@ static int hdev_open(BlockDriverState *bs, const char *filename, int flags)
if ( bsdPath[ 0 ] != '\0' ) {
strcat(bsdPath,"s0");
/* some CDs don't have a partition 0 */
- fd = open(bsdPath, O_RDONLY | O_BINARY | O_LARGEFILE);
+ fd = file_open(bsdPath, O_RDONLY | O_BINARY | O_LARGEFILE, 0);
if (fd < 0) {
bsdPath[strlen(bsdPath)-1] = '1';
} else {
@@ -798,7 +798,7 @@ static int fd_open(BlockDriverState *bs)
#endif
return -EIO;
}
- s->fd = open(bs->filename, s->open_flags & ~O_NONBLOCK);
+ s->fd = file_open(bs->filename, s->open_flags & ~O_NONBLOCK, 0);
if (s->fd < 0) {
s->fd_error_time = get_clock();
s->fd_got_error = 1;
@@ -872,7 +872,7 @@ static int hdev_create(const char *filename, QEMUOptionParameter *options)
options++;
}
- fd = open(filename, O_WRONLY | O_BINARY);
+ fd = file_open(filename, O_WRONLY | O_BINARY, 0);
if (fd < 0)
return -errno;
@@ -950,7 +950,7 @@ static int floppy_probe_device(const char *filename)
if (strstart(filename, "/dev/fd", NULL))
prio = 50;
- fd = open(filename, O_RDONLY | O_NONBLOCK);
+ fd = file_open(filename, O_RDONLY | O_NONBLOCK, 0);
if (fd < 0) {
goto out;
}
@@ -1003,7 +1003,7 @@ static void floppy_eject(BlockDriverState *bs, bool eject_flag)
close(s->fd);
s->fd = -1;
}
- fd = open(bs->filename, s->open_flags | O_NONBLOCK);
+ fd = file_open(bs->filename, s->open_flags | O_NONBLOCK, 0);
if (fd >= 0) {
if (ioctl(fd, FDEJECT, 0) < 0)
perror("FDEJECT");
@@ -1053,7 +1053,7 @@ static int cdrom_probe_device(const char *filename)
int prio = 0;
struct stat st;
- fd = open(filename, O_RDONLY | O_NONBLOCK);
+ fd = file_open(filename, O_RDONLY | O_NONBLOCK, 0);
if (fd < 0) {
goto out;
}
@@ -1177,7 +1177,7 @@ static int cdrom_reopen(BlockDriverState *bs)
*/
if (s->fd >= 0)
close(s->fd);
- fd = open(bs->filename, s->open_flags, 0644);
+ fd = file_open(bs->filename, s->open_flags, 0644);
if (fd < 0) {
s->fd = -1;
return -EIO;
diff --git a/block/raw-win32.c b/block/raw-win32.c
index e4b0b75..ec4ac96 100644
--- a/block/raw-win32.c
+++ b/block/raw-win32.c
@@ -255,8 +255,8 @@ static int raw_create(const char *filename, QEMUOptionParameter *options)
options++;
}
- fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY,
- 0644);
+ fd = file_open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY,
+ 0644);
if (fd < 0)
return -EIO;
set_sparse(fd);
diff --git a/block/vdi.c b/block/vdi.c
index 119d3c7..b3ec9b2 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -648,8 +648,8 @@ static int vdi_create(const char *filename, QEMUOptionParameter *options)
options++;
}
- fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY | O_LARGEFILE,
- 0644);
+ fd = file_open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY | O_LARGEFILE,
+ 0644);
if (fd < 0) {
return -errno;
}
diff --git a/block/vmdk.c b/block/vmdk.c
index 18e9b4c..bda4c1a 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1161,10 +1161,9 @@ static int vmdk_create_extent(const char *filename, int64_t filesize,
VMDK4Header header;
uint32_t tmp, magic, grains, gd_size, gt_size, gt_count;
- fd = open(
- filename,
- O_WRONLY | O_CREAT | O_TRUNC | O_BINARY | O_LARGEFILE,
- 0644);
+ fd = file_open(filename,
+ O_WRONLY | O_CREAT | O_TRUNC | O_BINARY | O_LARGEFILE,
+ 0644);
if (fd < 0) {
return -errno;
}
@@ -1484,15 +1483,13 @@ static int vmdk_create(const char *filename, QEMUOptionParameter *options)
(flags & BLOCK_FLAG_COMPAT6 ? 6 : 4),
total_size / (int64_t)(63 * 16 * 512));
if (split || flat) {
- fd = open(
- filename,
- O_WRONLY | O_CREAT | O_TRUNC | O_BINARY | O_LARGEFILE,
- 0644);
+ fd = file_open(filename,
+ O_WRONLY | O_CREAT | O_TRUNC | O_BINARY | O_LARGEFILE,
+ 0644);
} else {
- fd = open(
- filename,
- O_WRONLY | O_BINARY | O_LARGEFILE,
- 0644);
+ fd = file_open(filename,
+ O_WRONLY | O_BINARY | O_LARGEFILE,
+ 0644);
}
if (fd < 0) {
return -errno;
diff --git a/block/vpc.c b/block/vpc.c
index 5cd13d1..c1efb10 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -678,7 +678,7 @@ static int vpc_create(const char *filename, QEMUOptionParameter *options)
}
/* Create the file */
- fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, 0644);
+ fd = file_open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, 0644);
if (fd < 0) {
return -EIO;
}
diff --git a/block/vvfat.c b/block/vvfat.c
index 2dc9d50..1573d8f 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -1156,7 +1156,7 @@ static int open_file(BDRVVVFATState* s,mapping_t* mapping)
if(!s->current_mapping ||
strcmp(s->current_mapping->path,mapping->path)) {
/* open file */
- int fd = open(mapping->path, O_RDONLY | O_BINARY | O_LARGEFILE);
+ int fd = file_open(mapping->path, O_RDONLY | O_BINARY | O_LARGEFILE, 0);
if(fd<0)
return -1;
vvfat_close_current_file(s);
@@ -2215,7 +2215,7 @@ static int commit_one_file(BDRVVVFATState* s,
for (i = s->cluster_size; i < offset; i += s->cluster_size)
c = modified_fat_get(s, c);
- fd = open(mapping->path, O_RDWR | O_CREAT | O_BINARY, 0666);
+ fd = file_open(mapping->path, O_RDWR | O_CREAT | O_BINARY, 0666);
if (fd < 0) {
fprintf(stderr, "Could not open %s... (%s, %d)\n", mapping->path,
strerror(errno), errno);
diff --git a/block_int.h b/block_int.h
index b80e66d..f3b6144 100644
--- a/block_int.h
+++ b/block_int.h
@@ -453,4 +453,16 @@ void stream_start(BlockDriverState *bs, BlockDriverState *base,
BlockDriverCompletionFunc *cb,
void *opaque, Error **errp);
+/**
+ * file_open:
+ * @filename: the filename to attempt to open
+ * @flags: O_ flags that determine how the file is open
+ * @mode: the mode to create the file with if #O_CREAT is included in @flags
+ *
+ * This function behaves just like the @open libc function. It may, however,
+ * get the file descriptor from the QEMU command line or monitor if QEMU is
+ * being run with fewer privileges.
+ */
+int file_open(const char *filename, int flags, mode_t mode);
+
#endif /* BLOCK_INT_H */
diff --git a/vl.c b/vl.c
index 23ab3a3..6a55166 100644
--- a/vl.c
+++ b/vl.c
@@ -3201,6 +3201,12 @@ int main(int argc, char **argv, char **envp)
case QEMU_OPTION_qtest_log:
qtest_log = optarg;
break;
+ case QEMU_OPTION_filefd:
+ opts = qemu_opts_parse(qemu_find_opts("filefd"), optarg, 0);
+ if (!opts) {
+ exit(1);
+ }
+ break;
default:
os_parse_cmd_args(popt->index, optarg);
}
--
1.7.7.6
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