Hi,
I am seeing abnormal kernel<->userland interaction for range-exceeding
offsets during readdir.
A suggested patch for btrfs is below, but I think there could also
be involvement of (read: a bug in) Glibc.
Would the copied parties please have a look, as it may spans both glibc
and btrfs.
Thanks,
Jan
parent 81841fa96da5597a411f5f274a664f186b2d2549 (v2.6.29-rc2-21-g81841fa)
commit fa8ea6611fedecba8e5fdf2a5dfd82affa5a982e
Author: Jan Engelhardt <jengelh@medozas.de>
Date: Sat Jan 17 20:26:25 2009 +0100
btrfs: readdir problem workaround for 32-bit off_t
Kernel is i586, as is the userland.
btrfs sets filp->f_pos == (2^63-1) when it has reached the
end of a directory. This is problematic.
In obtuse 32-bit mode (no _FILE_OFFSET_BITS), readdir(3) will not return
the last entry.
However, when compiled with -D_FILE_OFFSET_BITS=64, it will return the
last entry. But telldir() will return (uint32_t)-1, which does not quite
match up with the 2^63-1.
$ cat test.c
#include <dirent.h>
#include <stdio.h>
int main(int argc, const char **argv)
{
DIR *r = opendir(argv[1]);
struct dirent *de;
while ((de = readdir(r)) != NULL)
printf("%lld %s\n", (long long)telldir(r), de->d_name);
return 0;
}
$ gcc test.c -o test -ggdb3
$ ./test /tmp/z
2 .
2 ..
3 a
4 b
5 lib
$ gcc test.c -o test -ggdb3 -D_FILE_OFFSET_BITS=64
$ ./test /tmp/z
2 .
2 ..
3 a
4 b
5 lib
4294967295 strace.log
This has deep effects and my boot hangs. (Got btrfs as the root fs.)
I have no idea who exactly of Glibc and btrfs is at fault with what,
but this change makes btrfs usable for the moment.
Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
---
fs/btrfs/inode.c | 5 +----
1 files changed, 1 insertions(+), 4 deletions(-)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 8adfe05..901be02 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3264,10 +3264,7 @@ skip:
}
/* Reached end of directory/root. Bump pos past the last item. */
- if (key_type == BTRFS_DIR_INDEX_KEY)
- filp->f_pos = INT_LIMIT(typeof(filp->f_pos));
- else
- filp->f_pos++;
+ filp->f_pos++;
nopos:
ret = 0;
err:
--
# Created with git-export-patch
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