[lvm-devel] master - device: Remove some data copying between buffers.
Alasdair Kergon
agk at sourceware.org
Wed Jan 10 15:53:37 UTC 2018
Gitweb: https://sourceware.org/git/?p=lvm2.git;a=commitdiff;h=dcb2a5a6116ed4853933e1a72e185a8109aab9cc
Commit: dcb2a5a6116ed4853933e1a72e185a8109aab9cc
Parent: 4d568b709cec5f84c8a8a278747b997a75b4c463
Author: Alasdair G Kergon <agk at redhat.com>
AuthorDate: Wed Jan 10 13:18:56 2018 +0000
Committer: Alasdair G Kergon <agk at redhat.com>
CommitterDate: Wed Jan 10 15:48:03 2018 +0000
device: Remove some data copying between buffers.
Callers that read larger amounts of data now get a pointer to read-only
data directly without copying it through an intermediate buffer. This
data is owned by the device layer so the callers no longer free it.
---
lib/config/config.c | 4 +---
lib/device/dev-io.c | 38 ++++++++++++++++++--------------------
lib/device/device.h | 1 +
lib/format_text/format-text.c | 6 +-----
lib/label/label.c | 2 --
5 files changed, 21 insertions(+), 30 deletions(-)
diff --git a/lib/config/config.c b/lib/config/config.c
index 7217cd9..9dd8a61 100644
--- a/lib/config/config.c
+++ b/lib/config/config.c
@@ -534,9 +534,6 @@ static void _process_config_file_buffer(int failed, void *context, void *data)
}
out:
- if (!failed && !pcfp->use_mmap)
- dm_free(data);
-
if (pcfp->config_file_read_fd_callback)
pcfp->config_file_read_fd_callback(!pcfp->ret, pcfp->config_file_read_fd_context, NULL);
}
@@ -612,6 +609,7 @@ int config_file_read_fd(struct dm_pool *mem, struct dm_config_tree *cft, struct
if (!(buf = dev_read_circular(dev, (uint64_t) offset, size, (uint64_t) offset2, size2, reason)))
goto_out;
_process_config_file_buffer(0, pcfp, buf);
+ dm_free(buf);
} else if (!dev_read_callback(dev, (uint64_t) offset, size, reason, _process_config_file_buffer, pcfp))
goto_out;
r = pcfp->ret;
diff --git a/lib/device/dev-io.c b/lib/device/dev-io.c
index 18a09d1..30e4235 100644
--- a/lib/device/dev-io.c
+++ b/lib/device/dev-io.c
@@ -284,7 +284,7 @@ static int _aligned_io(struct device_area *where, char *buffer,
where->size, (uint64_t) where->start, widened.size, (uint64_t) widened.start, dev_name(where->dev), _reason_text(reason));
}
- if (!buffer_was_widened && !((uintptr_t) buffer & mask))
+ if (should_write && !buffer_was_widened && !((uintptr_t) buffer & mask))
/* Perform the I/O directly. */
bounce = buffer;
#ifndef DEBUG_MEM
@@ -308,7 +308,7 @@ static int _aligned_io(struct device_area *where, char *buffer,
}
#endif
- devbuf = EXTRA_IO(reason) ? &where->dev->last_extra_devbuf : &where->dev->last_devbuf;
+ devbuf = DEV_DEVBUF(where->dev, reason);
_release_devbuf(devbuf);
devbuf->malloc_address = bounce_buf;
devbuf->buf = bounce;
@@ -345,9 +345,6 @@ static int _aligned_io(struct device_area *where, char *buffer,
}
/* read */
- if (bounce_buf)
- memcpy(buffer, bounce + (where->start - widened.start),
- (size_t) where->size);
/* We store what we just read as it often also satisfies the next request */
devbuf->data = bounce + (where->start - widened.start);
@@ -782,7 +779,10 @@ static void _dev_inc_error_count(struct device *dev)
dev->max_error_count, dev_name(dev));
}
-static int _dev_read(struct device *dev, uint64_t offset, size_t len, dev_io_reason_t reason, char *buf)
+/*
+ * Data is returned (read-only) at dev->last_[extra_]devbuf->data
+ */
+static int _dev_read(struct device *dev, uint64_t offset, size_t len, dev_io_reason_t reason)
{
struct device_area where;
int ret;
@@ -797,7 +797,7 @@ static int _dev_read(struct device *dev, uint64_t offset, size_t len, dev_io_rea
where.start = offset;
where.size = len;
- ret = _aligned_io(&where, buf, 0, reason);
+ ret = _aligned_io(&where, NULL, 0, reason);
if (!ret)
_dev_inc_error_count(dev);
@@ -814,30 +814,24 @@ char *dev_read(struct device *dev, uint64_t offset, size_t len, dev_io_reason_t
return NULL;
}
- if (!_dev_read(dev, offset, len, reason, buf)) {
+ if (!_dev_read(dev, offset, len, reason)) {
log_error("Read from %s failed", dev_name(dev));
dm_free(buf);
return NULL;
}
+ memcpy(buf, DEV_DEVBUF(dev, reason)->data, len);
+
return buf;
}
-/* Callback fn is responsible for dm_free */
int dev_read_callback(struct device *dev, uint64_t offset, size_t len, dev_io_reason_t reason,
lvm_callback_fn_t dev_read_callback_fn, void *callback_context)
{
- char *buf;
int r = 0;
- if (!(buf = dm_malloc(len))) {
- log_error("Buffer allocation failed for device read.");
- goto out;
- }
-
- if (!_dev_read(dev, offset, len, reason, buf)) {
+ if (!_dev_read(dev, offset, len, reason)) {
log_error("Read from %s failed", dev_name(dev));
- dm_free(buf);
goto out;
}
@@ -845,7 +839,7 @@ int dev_read_callback(struct device *dev, uint64_t offset, size_t len, dev_io_re
out:
if (dev_read_callback_fn)
- dev_read_callback_fn(!r, callback_context, buf);
+ dev_read_callback_fn(!r, callback_context, DEV_DEVBUF(dev, reason)->data);
return r;
}
@@ -879,18 +873,22 @@ char *dev_read_circular(struct device *dev, uint64_t offset, size_t len,
return NULL;
}
- if (!_dev_read(dev, offset, len, reason, buf)) {
+ if (!_dev_read(dev, offset, len, reason)) {
log_error("Read from %s failed", dev_name(dev));
dm_free(buf);
return NULL;
}
- if (!_dev_read(dev, offset2, len2, reason, buf + len)) {
+ memcpy(buf, DEV_DEVBUF(dev, reason)->data, len);
+
+ if (!_dev_read(dev, offset2, len2, reason)) {
log_error("Circular read from %s failed", dev_name(dev));
dm_free(buf);
return NULL;
}
+ memcpy(buf + len, DEV_DEVBUF(dev, reason)->data, len2);
+
return buf;
}
diff --git a/lib/device/device.h b/lib/device/device.h
index 1728596..cf44362 100644
--- a/lib/device/device.h
+++ b/lib/device/device.h
@@ -124,6 +124,7 @@ typedef enum dev_io_reason {
* Is this I/O for a device's extra metadata area?
*/
#define EXTRA_IO(reason) ((reason) == DEV_IO_MDA_EXTRA_HEADER || (reason) == DEV_IO_MDA_EXTRA_CONTENT)
+#define DEV_DEVBUF(dev, reason) (EXTRA_IO((reason)) ? &(dev)->last_extra_devbuf : &(dev)->last_devbuf)
struct device_list {
struct dm_list list;
diff --git a/lib/format_text/format-text.c b/lib/format_text/format-text.c
index 7e80a11..26a5007 100644
--- a/lib/format_text/format-text.c
+++ b/lib/format_text/format-text.c
@@ -385,9 +385,6 @@ static void _process_raw_mda_header(int failed, void *context, void *data)
bad:
prmp->ret = 0;
out:
- if (!failed)
- dm_free(data);
-
if (prmp->ret && prmp->mdah_callback_fn)
prmp->mdah_callback_fn(0, prmp->mdah_callback_context, mdah);
}
@@ -1474,8 +1471,7 @@ static void _vgname_from_mda_validate(int failed, void *context, void *data)
}
out:
- if (!failed)
- dm_free(data);
+ ;
}
int vgname_from_mda(const struct format_type *fmt,
diff --git a/lib/label/label.c b/lib/label/label.c
index 362a1b0..919a507 100644
--- a/lib/label/label.c
+++ b/lib/label/label.c
@@ -226,8 +226,6 @@ static void _find_labeller(int failed, void *context, void *data)
}
}
- dm_free(readbuf);
-
if (!l) {
if ((info = lvmcache_info_from_pvid(dev->pvid, dev, 0)))
_update_lvmcache_orphan(info);
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