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infra: new Lamport ordering method

This commit is contained in:
Thomas Schoebel-Theuer 2020-03-01 16:06:24 +01:00
parent 722d99487f
commit 7d6bdf945f
1 changed files with 47 additions and 2 deletions
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49
kernel/sy_old/sy_generic.c
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@ -886,6 +886,8 @@ EXPORT_SYMBOL_GPL(mars_remaining_space);
/* Timestamp Ordering */
/* Description of the OLD odering method:
*/
/* Timestamp ordering (e.g. via Lamport Clock) is easy when
* the object exists.
* When unlink() comes into play, it becomes more complex:
@ -896,9 +898,14 @@ EXPORT_SYMBOL_GPL(mars_remaining_space);
* Idea: use a substitute object ".deleted-$object".
*/
int compat_deletions = 1;
static DEFINE_MUTEX(ordered_lock);
int ordered_unlink(const char *path, const struct lamport_time *stamp, int serial, int mode)
static
int compat_ordered_unlink(const char *path,
const struct lamport_time *stamp,
int serial, int mode)
{
struct kstat stat;
char serial_str[32];
@ -934,7 +941,10 @@ int ordered_unlink(const char *path, const struct lamport_time *stamp, int seria
return status;
}
int ordered_symlink(const char *oldpath, const char *newpath, const struct lamport_time *stamp)
static
int compat_ordered_symlink(const char *oldpath,
const char *newpath,
const struct lamport_time *stamp)
{
struct kstat stat;
struct lamport_time now;
@ -968,6 +978,18 @@ int ordered_symlink(const char *oldpath, const char *newpath, const struct lampo
return status;
}
/* NEW timestamp ordering method.
* Timestamp ordering (e.g. via Lamport Clock) is easy when
* the object exists.
* When unlink() comes into play, it becomes more complex:
* where to store the timestamp of the object when it is
* deleted?
* The new method simply uses a special value MARS_DELETED_STR
* as a marker for symlinks.
* In order to prevent long-term accumulation of suchalike
* "zombie" symlinks, some cleanup via unlink() is necessary.
* We offload cleanup to "marsadm cron".
*/
char *ordered_readlink(const char *path)
{
@ -979,6 +1001,29 @@ char *ordered_readlink(const char *path)
return res;
}
int ordered_unlink(const char *path,
const struct lamport_time *stamp,
int serial, int mode)
{
if (compat_deletions)
return compat_ordered_unlink(path, stamp, serial, mode);
return ordered_symlink(MARS_DELETED_STR, path, stamp);
}
int ordered_symlink(const char *oldpath,
const char *newpath,
const struct lamport_time *stamp)
{
int status;
if (compat_deletions)
return compat_ordered_symlink(oldpath, newpath, stamp);
status = mars_symlink(oldpath, newpath, stamp, true);
return status;
}
//////////////////////////////////////////////////////////////
// thread binding