Hello
Charles P. Wright wrote:
> Vladimir,
>
> We actually came across this while working on Unionfs in the kernel,
> which uses lseek to inquire about directory positions and then resume
> directory reading operations (much like nfsd does).
>
Ok, please try whether the attached patch makes reiser4 to behave similar to
others.
> I've attached a user space program that demonstrates the behavior.
>
> The relevant strace entries are:
> open("/mnt/r4/", O_RDONLY) = 3
> getdents(3, /* 5 entries */, 268) = 80
> lseek(3, 0, SEEK_CUR) = -1 ENOENT
> lseek(3, 4294967295, SEEK_SET) = -1 EINVAL
>
> The third line is the one of concern.
>
> The same program run on another file system yields a trace like:
> open("/mnt", O_RDONLY) = 3
> getdents(3, /* 4 entries */, 268) = 68
> lseek(3, 0, SEEK_CUR) = 2147483647
> lseek(3, 2147483647, SEEK_SET) = 2147483647
>
> Charles
>
> On Mon, 2005-08-22 at 20:19 +0400, Vladimir V. Saveliev wrote:
>>Hello
>>
>>Charles P. Wright wrote:
>>>Hello,
>>>
>>>I've noticed that Reiser4's behavior deviates from other file systems
>>>when seeking with directories. After reading a directory, if you run
>>>vfs_lseek(dir, 0, SEEK_CUR), then -ENOENT is returned. This means that
>>>you can't pass the identifier back to vfs_lseek with SEEK_SET.
>>>
>>Would you please send your test program?
>>
>>------------------------------------------------------------------------
>>
>>#include <stdio.h>
>>#include <linux/types.h>
>>#include <linux/unistd.h>
>>#include <linux/dirent.h>
>>#include <sys/types.h>
>>#include <fcntl.h>
>>#include <sys/errno.h>
>>#include <unistd.h>
>>#include <stdlib.h>
>>
>>_syscall3(int, getdents, uint, fd, struct dirent *, dirp, uint, count);
>>
>>int main(int argc, char *argv[])
>>{
>> struct dirent dirent;
>> int fd;
>> int nread;
>> struct dirent *p;
>> off_t offset;
>>
>> if (argc != 2) {
>> fprintf(stderr, "No dir specified\n");
>> exit(1);
>> }
>>
>> if ((fd = open(argv[1], O_RDONLY)) < 0) {
>> fprintf(stderr, "Could not open directory %s\n", argv[1]);
>> exit(2);
>> }
>>
>> while ((nread = getdents(fd, &dirent, sizeof(dirent))) > 0) {
>> p = &dirent;
>> while (nread > 0) {
>> printf("d_reclen = %d, d_name = %s, d_off = %lu\n",
>> p->d_reclen, p->d_name, p->d_off);
>> nread -= p->d_reclen;
>> p = (struct dirent *)((char *)p + p->d_reclen);
>> }
>> offset = lseek(fd, 0, SEEK_CUR);
>> printf("Offset is %llu\n", offset);
offset is off_t. off_t is long int in this program.
You should have therefore
printf("Offset is %ld\n", offset);
>> if (lseek(fd, offset, SEEK_SET) < 0) {
>> perror("lseek");
>> exit(1);
>> }
>> }
>> exit(0);
>>}
This patch changes lseek part the end of reiser4 directory to not return ENOENT.
fs/reiser4/plugin/dir/dir.c | 9 ++++++---
1 files changed, 6 insertions(+), 3 deletions(-)
diff -puN fs/reiser4/plugin/dir/dir.c~reiser4-fix-llseek
fs/reiser4/plugin/dir/dir.c
--- linux-2.6.12-rc6-mm1/fs/reiser4/plugin/dir/dir.c~reiser4-fix-llseek
2005-08-23 15:22:43.363256896 +0400
+++ linux-2.6.12-rc6-mm1-vs/fs/reiser4/plugin/dir/dir.c 2005-08-23
15:59:29.523105778 +0400
@@ -854,7 +854,10 @@ dir_rewind(struct file *dir, readdir_pos
memset(pos, 0, sizeof *pos);
return dir_go_to(dir, pos, tap);
} else if (destination >= inode->i_size)
- return RETERR(-ENOENT);
+ /* seek past the end of directory */
+ dir->f_pos = inode->i_size;
+ return 0;
+ }
if (shift < 0) {
/* I am afraid of negative numbers */
@@ -1629,7 +1632,7 @@ readdir_common(struct file *f /* directo
repeat:
result = dir_readdir_init(f, &tap, &pos);
- if (result == 0) {
+ if (result == 0 && f->f_pos != inode->i_size) {
result = tap_load(&tap);
/* scan entries one by one feeding them to @filld */
while (result == 0) {
@@ -1669,7 +1672,7 @@ readdir_common(struct file *f /* directo
if (result >= 0)
f->f_version = inode->i_version;
- } else if (result == -E_NO_NEIGHBOR || result == -ENOENT)
+ } else if (result == -E_NO_NEIGHBOR || f->f_pos == inode->i_size ||
result == -ENOENT)
result = 0;
tap_done(&tap);
detach_fsdata(f);
_
