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printing: traverse_read the printer list for share updates

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The printcap update procedure involves the background printer process
obtaining the printcap information from the printing backend, writing
this to printer_list.tdb, and then notifying all smbd processes of the
new list. The processes then all attempt to simultaneously traverse
printer_list.tdb, in order to update their local share lists.

With a large number of printers, and a large number of per-client smbd
processes, this traversal results in significant lock contention, mostly
due to the fact that the traversal is unnecessarily done with an
exclusive (write) lock on the printer_list.tdb database.

This commit changes the share update code path to perform a read-only
traversal.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=10652

Reported-by: Alex K <korobkin+samba@gmail.com>
Reported-by: Franz Pförtsch <franz.pfoertsch@brose.com>
Signed-off-by: David Disseldorp <ddiss@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>
This commit is contained in:
David Disseldorp 2014-07-10 00:18:10 +02:00 committed by Andreas Schneider
parent 9c5470be1e
commit 1e83435eac
5 changed files with 17 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
source3/printing/load.c
View File

@ -71,5 +71,5 @@ void load_printers(struct tevent_context *ev,
/* load all printcap printers */
if (lp_load_printers() && lp_servicenumber(PRINTERS_NAME) >= 0)
pcap_printer_fn(lp_add_one_printer, NULL);
pcap_printer_read_fn(lp_add_one_printer, NULL);
}

4
source3/printing/pcap.c
View File

@ -229,11 +229,11 @@ void pcap_printer_fn_specific(const struct pcap_cache *pc,
return;
}
void pcap_printer_fn(void (*fn)(const char *, const char *, const char *, void *), void *pdata)
void pcap_printer_read_fn(void (*fn)(const char *, const char *, const char *, void *), void *pdata)
{
NTSTATUS status;
status = printer_list_run_fn(fn, pdata);
status = printer_list_read_run_fn(fn, pdata);
if (!NT_STATUS_IS_OK(status)) {
DEBUG(3, ("Failed to run fn for all printers!\n"));
}

2
source3/printing/pcap.h
View File

@ -39,7 +39,7 @@ bool pcap_cache_add(const char *name, const char *comment, const char *location)
bool pcap_cache_loaded(void);
bool pcap_cache_replace(const struct pcap_cache *cache);
void pcap_printer_fn_specific(const struct pcap_cache *, void (*fn)(const char *, const char *, const char *, void *), void *);
void pcap_printer_fn(void (*fn)(const char *, const char *, const char *, void *), void *);
void pcap_printer_read_fn(void (*fn)(const char *, const char *, const char *, void *), void *);
void pcap_cache_reload(struct tevent_context *ev,
struct messaging_context *msg_ctx,

17
source3/printing/printer_list.c
View File

@ -284,7 +284,8 @@ done:
typedef int (printer_list_trv_fn_t)(struct db_record *, void *);
static NTSTATUS printer_list_traverse(printer_list_trv_fn_t *fn,
void *private_data)
void *private_data,
bool read_only)
{
struct db_context *db;
NTSTATUS status;
@ -294,7 +295,11 @@ static NTSTATUS printer_list_traverse(printer_list_trv_fn_t *fn,
return NT_STATUS_INTERNAL_DB_CORRUPTION;
}
status = dbwrap_traverse(db, fn, private_data, NULL);
if (read_only) {
status = dbwrap_traverse_read(db, fn, private_data, NULL);
} else {
status = dbwrap_traverse(db, fn, private_data, NULL);
}
return status;
}
@ -364,7 +369,7 @@ NTSTATUS printer_list_clean_old(void)
state.status = NT_STATUS_OK;
status = printer_list_traverse(printer_list_clean_fn, &state);
status = printer_list_traverse(printer_list_clean_fn, &state, false);
if (NT_STATUS_EQUAL(status, NT_STATUS_UNSUCCESSFUL) &&
!NT_STATUS_IS_OK(state.status)) {
status = state.status;
@ -417,8 +422,8 @@ static int printer_list_exec_fn(struct db_record *rec, void *private_data)
return 0;
}
NTSTATUS printer_list_run_fn(void (*fn)(const char *, const char *, const char *, void *),
void *private_data)
NTSTATUS printer_list_read_run_fn(void (*fn)(const char *, const char *, const char *, void *),
void *private_data)
{
struct printer_list_exec_state state;
NTSTATUS status;
@ -427,7 +432,7 @@ NTSTATUS printer_list_run_fn(void (*fn)(const char *, const char *, const char *
state.private_data = private_data;
state.status = NT_STATUS_OK;
status = printer_list_traverse(printer_list_exec_fn, &state);
status = printer_list_traverse(printer_list_exec_fn, &state, true);
if (NT_STATUS_EQUAL(status, NT_STATUS_UNSUCCESSFUL) &&
!NT_STATUS_IS_OK(state.status)) {
status = state.status;

4
source3/printing/printer_list.h
View File

@ -100,6 +100,6 @@ NTSTATUS printer_list_mark_reload(void);
*/
NTSTATUS printer_list_clean_old(void);
NTSTATUS printer_list_run_fn(void (*fn)(const char *, const char *, const char *, void *),
void *private_data);
NTSTATUS printer_list_read_run_fn(void (*fn)(const char *, const char *, const char *, void *),
void *private_data);
#endif /* _PRINTER_LIST_H_ */