Messages in this thread Patch in this message | | | Date | Sat, 17 Jan 2009 20:39:17 +0100 (CET) | From | Jan Engelhardt <> | Subject | btrfs: readdir problem workaround for 32-bit off_t |
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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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