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[Qemu-devel] [PATCH v3 1/4] block: make bdrv_find_backing_image compare
From: |
Jeff Cody |
Subject: |
[Qemu-devel] [PATCH v3 1/4] block: make bdrv_find_backing_image compare canonical filenames |
Date: |
Tue, 16 Oct 2012 15:49:09 -0400 |
Currently, bdrv_find_backing_image compares bs->backing_file with
what is passed in as a backing_file name. Mismatches may occur,
however, when bs->backing_file and backing_file are not both
absolute or relative.
Use path_combine() to make sure any relative backing filenames are
relative to the current image filename being searched, and then use
realpath() to make all comparisons based on absolute filenames.
If either backing_file or bs->backing_file is determine to be a
protocol, then no filename normalization is performed.
This also changes bdrv_find_backing_image to no longer be recursive,
but iterative.
Signed-off-by: Jeff Cody <address@hidden>
---
block.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 54 insertions(+), 6 deletions(-)
diff --git a/block.c b/block.c
index e95f613..5e7fc9e 100644
--- a/block.c
+++ b/block.c
@@ -3123,22 +3123,70 @@ int bdrv_snapshot_load_tmp(BlockDriverState *bs,
return -ENOTSUP;
}
+/* backing_file can either be relative, or absolute, or a protocol. If it is
+ * relative, it must be relative to the chain. So, passing in bs->filename
+ * from a BDS as backing_file should not be done, as that may be relative to
+ * the CWD rather than the chain. */
BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
const char *backing_file)
{
- if (!bs->drv) {
+ char *filename_full = NULL;
+ char *backing_file_full = NULL;
+ char *filename_tmp = NULL;
+ int is_protocol = 0;
+ BlockDriverState *curr_bs = NULL;
+ BlockDriverState *retval = NULL;
+
+ if (!bs || !bs->drv || !backing_file) {
return NULL;
}
- if (bs->backing_hd) {
- if (strcmp(bs->backing_file, backing_file) == 0) {
- return bs->backing_hd;
+ filename_full = g_malloc(PATH_MAX);
+ backing_file_full = g_malloc(PATH_MAX);
+ filename_tmp = g_malloc(PATH_MAX);
+
+ is_protocol = path_has_protocol(backing_file);
+
+ for (curr_bs = bs; curr_bs->backing_hd; curr_bs = curr_bs->backing_hd) {
+
+ /* If either of the filename paths is actually a protocol, then
+ * compare unmodified paths; otherwise make paths relative */
+ if (is_protocol || path_has_protocol(curr_bs->backing_file)) {
+ if (strcmp(backing_file, curr_bs->backing_file) == 0) {
+ retval = curr_bs->backing_hd;
+ break;
+ }
} else {
- return bdrv_find_backing_image(bs->backing_hd, backing_file);
+ /* If not an absolute filename path, make it relative to the
current
+ * image's filename path */
+ path_combine(filename_tmp, PATH_MAX, curr_bs->filename,
+ backing_file);
+
+ /* We are going to compare absolute pathnames */
+ if (!realpath(filename_tmp, filename_full)) {
+ continue;
+ }
+
+ /* We need to make sure the backing filename we are comparing
against
+ * is relative to the current image filename (or absolute) */
+ path_combine(filename_tmp, PATH_MAX, curr_bs->filename,
+ curr_bs->backing_file);
+
+ if (!realpath(filename_tmp, backing_file_full)) {
+ continue;
+ }
+
+ if (strcmp(backing_file_full, filename_full) == 0) {
+ retval = curr_bs->backing_hd;
+ break;
+ }
}
}
- return NULL;
+ g_free(filename_full);
+ g_free(backing_file_full);
+ g_free(filename_tmp);
+ return retval;
}
int bdrv_get_backing_file_depth(BlockDriverState *bs)
--
1.7.11.4
- [Qemu-devel] [PATCH v3 0/4] block-commit fixes, Jeff Cody, 2012/10/16
- [Qemu-devel] [PATCH v3 1/4] block: make bdrv_find_backing_image compare canonical filenames,
Jeff Cody <=
- [Qemu-devel] [PATCH v3 2/4] block: in commit, determine base image from the top image, Jeff Cody, 2012/10/16
- [Qemu-devel] [PATCH v3 3/4] qemu-iotests: qemu-io tests update for block-commit (040), Jeff Cody, 2012/10/16
- [Qemu-devel] [PATCH v3 4/4] qemu-iotests: add relative backing file tests for block-commit (040), Jeff Cody, 2012/10/16
- Re: [Qemu-devel] [PATCH v3 0/4] block-commit fixes, Eric Blake, 2012/10/16