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Date: Thu, 28 Jul 2016 00:08:27 +0900
From: Namhyung Kim <namhyung@...nel.org>
To: kvm@...r.kernel.org, qemu-devel@...gnu.org,
virtualization@...ts.linux-foundation.org
Cc: LKML <linux-kernel@...r.kernel.org>,
Anton Vorontsov <anton@...msg.org>,
Colin Cross <ccross@...roid.com>,
Kees Cook <keescook@...omium.org>,
Tony Luck <tony.luck@...el.com>,
Matt Fleming <matt@...eblueprint.co.uk>,
linux-efi@...r.kernel.org
Subject: [PATCH 3/7] pstore: Manage buffer position for async write
Some pstore backend only supports async mode, so it's possible to do
some IO at the same time. In this case we need to manage the single
psinfo->buf not to broken by concurrent IO.
For example PSTORE_TYPE_CONSOLE IO is serialized by psinfo->buf_lock but
later IO can be issued before finishing previous request. In this case
it overwrites psinfo->buf so the previous result might be broken.
This patch adds psinfo->bufpos field to keep track of current position
in order to use psinfo->buf as a ring buffer. However it's just a
simple, best-effort way of doing that, and provides no 100% guarantee.
It's only effective for small concurrent IO like PSTORE_TYPE_CONSOLE
IMHO.
The new PSTORE_FLAGS_ASYNC flag enables management of buffer position.
The pstore_prepare_buf() is called before accessing the psinfo->buf and
the pstore_update_buf() is called after accessing the buf.
The pstore_get_buf() is provided for psinfo->write callback to determine
the current position of available buffer.
Cc: Anton Vorontsov <anton@...msg.org>
Cc: Colin Cross <ccross@...roid.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Tony Luck <tony.luck@...el.com>
Cc: Matt Fleming <matt@...eblueprint.co.uk>
Cc: linux-efi@...r.kernel.org
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
drivers/firmware/efi/efi-pstore.c | 2 +-
fs/pstore/platform.c | 48 +++++++++++++++++++++++++++++++--------
include/linux/pstore.h | 4 ++++
3 files changed, 44 insertions(+), 10 deletions(-)
diff --git a/drivers/firmware/efi/efi-pstore.c b/drivers/firmware/efi/efi-pstore.c
index 4daa5acd9117..ae0ffe259e07 100644
--- a/drivers/firmware/efi/efi-pstore.c
+++ b/drivers/firmware/efi/efi-pstore.c
@@ -259,7 +259,7 @@ static int efi_pstore_write(enum pstore_type_id type,
efivar_entry_set_safe(efi_name, vendor, PSTORE_EFI_ATTRIBUTES,
!pstore_cannot_block_path(reason),
- size, psi->buf);
+ size, pstore_get_buf(psi));
if (reason == KMSG_DUMP_OOPS)
efivar_run_worker();
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 76dd604a0f2c..26e2808cf554 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -150,6 +150,27 @@ bool pstore_cannot_block_path(enum kmsg_dump_reason reason)
}
EXPORT_SYMBOL_GPL(pstore_cannot_block_path);
+static void *pstore_prepare_buf(struct pstore_info *psi, size_t len)
+{
+ if (psi->bufpos + len > psi->bufsize ||
+ (psi->flags & PSTORE_FLAGS_ASYNC) == 0)
+ psi->bufpos = 0;
+
+ return psi->buf + psi->bufpos;
+}
+
+static void pstore_update_buf(struct pstore_info *psi, size_t len)
+{
+ if (psi->flags & PSTORE_FLAGS_ASYNC)
+ psi->bufpos += len;
+}
+
+void *pstore_get_buf(struct pstore_info *psi)
+{
+ return psi->buf + psi->bufpos;
+}
+EXPORT_SYMBOL_GPL(pstore_get_buf);
+
#ifdef CONFIG_PSTORE_ZLIB_COMPRESS
/* Derived from logfs_compress() */
static int compress_zlib(const void *in, void *out, size_t inlen, size_t outlen)
@@ -455,18 +476,21 @@ static size_t copy_kmsg_to_buffer(int hsize, size_t len)
{
size_t total_len;
size_t diff;
+ void *dst;
total_len = hsize + len;
+ dst = pstore_prepare_buf(psinfo, total_len);
if (total_len > psinfo->bufsize) {
diff = total_len - psinfo->bufsize + hsize;
- memcpy(psinfo->buf, big_oops_buf, hsize);
- memcpy(psinfo->buf + hsize, big_oops_buf + diff,
+ memcpy(dst, big_oops_buf, hsize);
+ memcpy(dst + hsize, big_oops_buf + diff,
psinfo->bufsize - hsize);
total_len = psinfo->bufsize;
} else
- memcpy(psinfo->buf, big_oops_buf, total_len);
+ memcpy(dst, big_oops_buf, total_len);
+ pstore_update_buf(psinfo, total_len);
return total_len;
}
@@ -500,7 +524,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
}
oopscount++;
while (total < kmsg_bytes) {
- char *dst;
+ char *dst, *buf;
unsigned long size;
int hsize;
int zipped_len = -1;
@@ -514,6 +538,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
} else {
dst = psinfo->buf;
size = psinfo->bufsize;
+ psinfo->bufpos = 0;
}
hsize = sprintf(dst, "%s#%d Part%u\n", why, oopscount, part);
@@ -524,8 +549,9 @@ static void pstore_dump(struct kmsg_dumper *dumper,
break;
if (big_oops_buf && is_locked) {
- zipped_len = pstore_compress(dst, psinfo->buf,
- hsize + len, psinfo->bufsize);
+ buf = pstore_prepare_buf(psinfo, hsize + len);
+ zipped_len = pstore_compress(dst, buf, hsize + len,
+ psinfo->bufsize - psinfo->bufpos);
if (zipped_len > 0) {
compressed = true;
@@ -543,6 +569,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
pstore_new_entry = 1;
total += total_len;
+ pstore_update_buf(psinfo, total_len);
part++;
}
if (is_locked)
@@ -573,6 +600,7 @@ static void pstore_console_write(struct console *con, const char *s, unsigned c)
while (s < e) {
unsigned long flags;
+ void *dst;
u64 id;
if (c > psinfo->bufsize)
@@ -584,8 +612,10 @@ static void pstore_console_write(struct console *con, const char *s, unsigned c)
} else {
spin_lock_irqsave(&psinfo->buf_lock, flags);
}
- memcpy(psinfo->buf, s, c);
+ dst = pstore_prepare_buf(psinfo, c);
+ memcpy(dst, s, c);
psinfo->write(PSTORE_TYPE_CONSOLE, 0, &id, 0, 0, 0, c, psinfo);
+ pstore_update_buf(psinfo, c);
spin_unlock_irqrestore(&psinfo->buf_lock, flags);
s += c;
c = e - s;
@@ -619,8 +649,8 @@ static int pstore_write_compat(enum pstore_type_id type,
bool compressed, size_t size,
struct pstore_info *psi)
{
- return psi->write_buf(type, reason, id, part, psinfo->buf, compressed,
- size, psi);
+ return psi->write_buf(type, reason, id, part, pstore_get_buf(psinfo),
+ compressed, size, psi);
}
/*
diff --git a/include/linux/pstore.h b/include/linux/pstore.h
index 9790904de6d2..14f524177b1f 100644
--- a/include/linux/pstore.h
+++ b/include/linux/pstore.h
@@ -52,6 +52,7 @@ struct pstore_info {
spinlock_t buf_lock; /* serialize access to 'buf' */
char *buf;
size_t bufsize;
+ size_t bufpos;
struct mutex read_mutex; /* serialize open/read/close */
int flags;
int (*open)(struct pstore_info *psi);
@@ -79,8 +80,11 @@ struct pstore_info {
#define PSTORE_FLAGS_FTRACE (1 << 2)
#define PSTORE_FLAGS_PMSG (1 << 3)
+#define PSTORE_FLAGS_ASYNC (1 << 30)
+
extern int pstore_register(struct pstore_info *);
extern void pstore_unregister(struct pstore_info *);
extern bool pstore_cannot_block_path(enum kmsg_dump_reason reason);
+extern void *pstore_get_buf(struct pstore_info *);
#endif /*_LINUX_PSTORE_H*/
--
2.8.0
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