summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorGustavo A. R. Silva <gustavoars@kernel.org>2020-05-07 14:22:10 -0500
committerSong Liu <songliubraving@fb.com>2020-05-13 12:02:23 -0700
commit358369f03ac94637c9fd9d8f94a2dfde86b9f25f (patch)
treeaad637516aada9aff42bad4332d9b442d54394df
parent3f99980c8f70bc56584450c0a69973eef7b65913 (diff)
md/raid1: Replace zero-length array with flexible-array
The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues. This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> Signed-off-by: Song Liu <songliubraving@fb.com>
-rw-r--r--drivers/md/md-linear.h2
-rw-r--r--drivers/md/raid1.h2
-rw-r--r--drivers/md/raid10.h2
3 files changed, 3 insertions, 3 deletions
diff --git a/drivers/md/md-linear.h b/drivers/md/md-linear.h
index 8381d651d4ed..24e97db50ebb 100644
--- a/drivers/md/md-linear.h
+++ b/drivers/md/md-linear.h
@@ -12,6 +12,6 @@ struct linear_conf
struct rcu_head rcu;
sector_t array_sectors;
int raid_disks; /* a copy of mddev->raid_disks */
- struct dev_info disks[0];
+ struct dev_info disks[];
};
#endif
diff --git a/drivers/md/raid1.h b/drivers/md/raid1.h
index e7ccad898736..b7eb09e8c025 100644
--- a/drivers/md/raid1.h
+++ b/drivers/md/raid1.h
@@ -180,7 +180,7 @@ struct r1bio {
* if the IO is in WRITE direction, then multiple bios are used.
* We choose the number when they are allocated.
*/
- struct bio *bios[0];
+ struct bio *bios[];
/* DO NOT PUT ANY NEW FIELDS HERE - bios array is contiguously alloced*/
};
diff --git a/drivers/md/raid10.h b/drivers/md/raid10.h
index d3eaaf3eb1bc..79cd2b7d3128 100644
--- a/drivers/md/raid10.h
+++ b/drivers/md/raid10.h
@@ -153,7 +153,7 @@ struct r10bio {
};
sector_t addr;
int devnum;
- } devs[0];
+ } devs[];
};
/* bits for r10bio.state */