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Remove dsm_resize() and dsm_remap().

Browse Source 
These interfaces were never used in core, didn't handle failure of
posix_fallocate() correctly and weren't supported on all platforms.
We agreed to remove them in 12.

Author: Thomas Munro
Reported-by: Andres Freund
Discussion: https://postgr.es/m/CAA4eK1%2B%3DyAFUvpFoHXFi_gm8YqmXN-TtkFH%2BVYjvDLS6-SFq-Q%40mail.gmail.com
This commit is contained in:
Thomas Munro 2018-11-06 16:11:12 +13:00
parent b0a1ff8a6a
commit 3c60d0fa23
4 changed files with 12 additions and 174 deletions
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32
src/backend/storage/ipc/dsm.c
View File

@ -653,38 +653,6 @@ dsm_detach_all(void)
&dsm_control_mapped_size, ERROR);
}
/*
* Resize an existing shared memory segment.
*
* This may cause the shared memory segment to be remapped at a different
* address. For the caller's convenience, we return the mapped address.
*/
void *
dsm_resize(dsm_segment *seg, Size size)
{
Assert(seg->control_slot != INVALID_CONTROL_SLOT);
dsm_impl_op(DSM_OP_RESIZE, seg->handle, size, &seg->impl_private,
&seg->mapped_address, &seg->mapped_size, ERROR);
return seg->mapped_address;
}
/*
* Remap an existing shared memory segment.
*
* This is intended to be used when some other process has extended the
* mapping using dsm_resize(), but we've still only got the initial
* portion mapped. Since this might change the address at which the
* segment is mapped, we return the new mapped address.
*/
void *
dsm_remap(dsm_segment *seg)
{
dsm_impl_op(DSM_OP_ATTACH, seg->handle, 0, &seg->impl_private,
&seg->mapped_address, &seg->mapped_size, ERROR);
return seg->mapped_address;
}
/*
* Detach from a shared memory segment, destroying the segment if we
* remove the last reference.

146
src/backend/storage/ipc/dsm_impl.c
View File

@ -127,14 +127,9 @@ int dynamic_shared_memory_type;
* map it.
*
* DSM_OP_ATTACH. Map the segment, whose size must be the request_size.
* The segment may already be mapped; any existing mapping should be removed
* before creating a new one.
*
* DSM_OP_DETACH. Unmap the segment.
*
* DSM_OP_RESIZE. Resize the segment to the given request_size and
* remap the segment at that new size.
*
* DSM_OP_DESTROY. Unmap the segment, if it is mapped. Destroy the
* segment.
*
@ -142,8 +137,7 @@ int dynamic_shared_memory_type;
* op: The operation to be performed.
* handle: The handle of an existing object, or for DSM_OP_CREATE, the
* a new handle the caller wants created.
* request_size: For DSM_OP_CREATE, the requested size. For DSM_OP_RESIZE,
* the new size. Otherwise, 0.
* request_size: For DSM_OP_CREATE, the requested size. Otherwise, 0.
* impl_private: Private, implementation-specific data. Will be a pointer
* to NULL for the first operation on a shared memory segment within this
* backend; thereafter, it will point to the value to which it was set
@ -165,7 +159,7 @@ dsm_impl_op(dsm_op op, dsm_handle handle, Size request_size,
void **impl_private, void **mapped_address, Size *mapped_size,
int elevel)
{
Assert(op == DSM_OP_CREATE || op == DSM_OP_RESIZE || request_size == 0);
Assert(op == DSM_OP_CREATE || request_size == 0);
Assert((op != DSM_OP_CREATE && op != DSM_OP_ATTACH) ||
(*mapped_address == NULL && *mapped_size == 0));
@ -198,31 +192,6 @@ dsm_impl_op(dsm_op op, dsm_handle handle, Size request_size,
}
}
/*
* Does the current dynamic shared memory implementation support resizing
* segments? (The answer here could be platform-dependent in the future,
* since AIX allows shmctl(shmid, SHM_RESIZE, &buffer), though you apparently
* can't resize segments to anything larger than 256MB that way. For now,
* we keep it simple.)
*/
bool
dsm_impl_can_resize(void)
{
switch (dynamic_shared_memory_type)
{
case DSM_IMPL_POSIX:
return true;
case DSM_IMPL_SYSV:
return false;
case DSM_IMPL_WINDOWS:
return false;
case DSM_IMPL_MMAP:
return true;
default:
return false; /* should not happen */
}
}
#ifdef USE_DSM_POSIX
/*
* Operating system primitives to support POSIX shared memory.
@ -296,7 +265,7 @@ dsm_impl_posix(dsm_op op, dsm_handle handle, Size request_size,
/*
* If we're attaching the segment, determine the current size; if we are
* creating or resizing the segment, set the size to the requested value.
* creating the segment, set the size to the requested value.
*/
if (op == DSM_OP_ATTACH)
{
@ -319,16 +288,14 @@ dsm_impl_posix(dsm_op op, dsm_handle handle, Size request_size,
}
request_size = st.st_size;
}
else if (*mapped_size != request_size &&
dsm_impl_posix_resize(fd, request_size) != 0)
else if (dsm_impl_posix_resize(fd, request_size) != 0)
{
int save_errno;
/* Back out what's already been done. */
save_errno = errno;
close(fd);
if (op == DSM_OP_CREATE)
shm_unlink(name);
shm_unlink(name);
errno = save_errno;
/*
@ -346,35 +313,6 @@ dsm_impl_posix(dsm_op op, dsm_handle handle, Size request_size,
return false;
}
/*
* If we're reattaching or resizing, we must remove any existing mapping,
* unless we've already got the right thing mapped.
*/
if (*mapped_address != NULL)
{
if (*mapped_size == request_size)
return true;
if (munmap(*mapped_address, *mapped_size) != 0)
{
int save_errno;
/* Back out what's already been done. */
save_errno = errno;
close(fd);
if (op == DSM_OP_CREATE)
shm_unlink(name);
errno = save_errno;
ereport(elevel,
(errcode_for_dynamic_shared_memory(),
errmsg("could not unmap shared memory segment \"%s\": %m",
name)));
return false;
}
*mapped_address = NULL;
*mapped_size = 0;
}
/* Map it. */
address = mmap(NULL, request_size, PROT_READ | PROT_WRITE,
MAP_SHARED | MAP_HASSEMAPHORE | MAP_NOSYNC, fd, 0);
@ -457,10 +395,9 @@ dsm_impl_posix_resize(int fd, off_t size)
* Operating system primitives to support System V shared memory.
*
* System V shared memory segments are manipulated using shmget(), shmat(),
* shmdt(), and shmctl(). There's no portable way to resize such
* segments. As the default allocation limits for System V shared memory
* are usually quite low, the POSIX facilities may be preferable; but
* those are not supported everywhere.
* shmdt(), and shmctl(). As the default allocation limits for System V
* shared memory are usually quite low, the POSIX facilities may be
* preferable; but those are not supported everywhere.
*/
static bool
dsm_impl_sysv(dsm_op op, dsm_handle handle, Size request_size,
@ -473,13 +410,6 @@ dsm_impl_sysv(dsm_op op, dsm_handle handle, Size request_size,
char name[64];
int *ident_cache;
/* Resize is not supported for System V shared memory. */
if (op == DSM_OP_RESIZE)
{
elog(elevel, "System V shared memory segments cannot be resized");
return false;
}
/* Since resize isn't supported, reattach is a no-op. */
if (op == DSM_OP_ATTACH && *mapped_address != NULL)
return true;
@ -670,13 +600,6 @@ dsm_impl_windows(dsm_op op, dsm_handle handle, Size request_size,
char name[64];
MEMORY_BASIC_INFORMATION info;
/* Resize is not supported for Windows shared memory. */
if (op == DSM_OP_RESIZE)
{
elog(elevel, "Windows shared memory segments cannot be resized");
return false;
}
/* Since resize isn't supported, reattach is a no-op. */
if (op == DSM_OP_ATTACH && *mapped_address != NULL)
return true;
@ -905,7 +828,7 @@ dsm_impl_mmap(dsm_op op, dsm_handle handle, Size request_size,
/*
* If we're attaching the segment, determine the current size; if we are
* creating or resizing the segment, set the size to the requested value.
* creating the segment, set the size to the requested value.
*/
if (op == DSM_OP_ATTACH)
{
@ -928,24 +851,7 @@ dsm_impl_mmap(dsm_op op, dsm_handle handle, Size request_size,
}
request_size = st.st_size;
}
else if (*mapped_size > request_size && ftruncate(fd, request_size))
{
int save_errno;
/* Back out what's already been done. */
save_errno = errno;
CloseTransientFile(fd);
if (op == DSM_OP_CREATE)
unlink(name);
errno = save_errno;
ereport(elevel,
(errcode_for_dynamic_shared_memory(),
errmsg("could not resize shared memory segment \"%s\" to %zu bytes: %m",
name, request_size)));
return false;
}
else if (*mapped_size < request_size)
else
{
/*
* Allocate a buffer full of zeros.
@ -985,8 +891,7 @@ dsm_impl_mmap(dsm_op op, dsm_handle handle, Size request_size,
/* Back out what's already been done. */
save_errno = errno;
CloseTransientFile(fd);
if (op == DSM_OP_CREATE)
unlink(name);
unlink(name);
errno = save_errno ? save_errno : ENOSPC;
ereport(elevel,
@ -997,35 +902,6 @@ dsm_impl_mmap(dsm_op op, dsm_handle handle, Size request_size,
}
}
/*
* If we're reattaching or resizing, we must remove any existing mapping,
* unless we've already got the right thing mapped.
*/
if (*mapped_address != NULL)
{
if (*mapped_size == request_size)
return true;
if (munmap(*mapped_address, *mapped_size) != 0)
{
int save_errno;
/* Back out what's already been done. */
save_errno = errno;
CloseTransientFile(fd);
if (op == DSM_OP_CREATE)
unlink(name);
errno = save_errno;
ereport(elevel,
(errcode_for_dynamic_shared_memory(),
errmsg("could not unmap shared memory segment \"%s\": %m",
name)));
return false;
}
*mapped_address = NULL;
*mapped_size = 0;
}
/* Map it. */
address = mmap(NULL, request_size, PROT_READ | PROT_WRITE,
MAP_SHARED | MAP_HASSEMAPHORE | MAP_NOSYNC, fd, 0);

4
src/include/storage/dsm.h
View File

@ -33,11 +33,9 @@ extern void dsm_detach_all(void);
extern void dsm_set_control_handle(dsm_handle h);
#endif
/* Functions that create, update, or remove mappings. */
/* Functions that create or remove mappings. */
extern dsm_segment *dsm_create(Size size, int flags);
extern dsm_segment *dsm_attach(dsm_handle h);
extern void *dsm_resize(dsm_segment *seg, Size size);
extern void *dsm_remap(dsm_segment *seg);
extern void dsm_detach(dsm_segment *seg);
/* Resource management functions. */

4
src/include/storage/dsm_impl.h
View File

@ -59,7 +59,6 @@ typedef enum
DSM_OP_CREATE,
DSM_OP_ATTACH,
DSM_OP_DETACH,
DSM_OP_RESIZE,
DSM_OP_DESTROY
} dsm_op;
@ -68,9 +67,6 @@ extern bool dsm_impl_op(dsm_op op, dsm_handle handle, Size request_size,
void **impl_private, void **mapped_address, Size *mapped_size,
int elevel);
/* Some implementations cannot resize segments. Can this one? */
extern bool dsm_impl_can_resize(void);
/* Implementation-dependent actions required to keep segment until shutdown. */
extern void dsm_impl_pin_segment(dsm_handle handle, void *impl_private,
void **impl_private_pm_handle);