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os_fs.c
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/*-
* Public Domain 2014-present MongoDB, Inc.
* Public Domain 2008-2014 WiredTiger, Inc.
*
* This is free and unencumbered software released into the public domain.
*
* Anyone is free to copy, modify, publish, use, compile, sell, or
* distribute this software, either in source code form or as a compiled
* binary, for any purpose, commercial or non-commercial, and by any
* means.
*
* In jurisdictions that recognize copyright laws, the author or authors
* of this software dedicate any and all copyright interest in the
* software to the public domain. We make this dedication for the benefit
* of the public at large and to the detriment of our heirs and
* successors. We intend this dedication to be an overt act of
* relinquishment in perpetuity of all present and future rights to this
* software under copyright law.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#include "wt_internal.h"
/*
* __posix_file_size --
* Get the size of a file in bytes, by file handle.
*/
static int
__posix_file_size(WT_FILE_HANDLE *file_handle, WT_SESSION *wt_session, wt_off_t *sizep)
{
struct stat sb;
WT_DECL_RET;
WT_FILE_HANDLE_POSIX *pfh;
WT_SESSION_IMPL *session;
session = (WT_SESSION_IMPL *)wt_session;
pfh = (WT_FILE_HANDLE_POSIX *)file_handle;
WT_SYSCALL(fstat(pfh->fd, &sb), ret);
if (ret == 0) {
*sizep = sb.st_size;
return (0);
}
WT_RET_MSG(session, ret, "%s: handle-size: fstat", file_handle->name);
}
/*
* __posix_unmap_file --
* Unmap the file.
*/
static void
__posix_unmap_file(WT_FILE_HANDLE *file_handle, WT_SESSION *wt_session)
{
WT_DECL_RET;
WT_FILE_HANDLE_POSIX *pfh;
WT_SESSION_IMPL *session;
session = (WT_SESSION_IMPL *)wt_session;
pfh = (WT_FILE_HANDLE_POSIX *)file_handle;
__wt_verbose(session, WT_VERB_FILEOPS, "%s, file-unmap: buffer=%p, size=%" PRId64,
file_handle->name, (void *)pfh->mmap_buf, pfh->mmap_size);
WT_ASSERT(session, pfh->mmap_buf != NULL);
ret = munmap(pfh->mmap_buf, (size_t)pfh->mmap_size);
pfh->mmap_buf = NULL;
pfh->mmap_size = 0;
if (ret != 0)
__wt_err(session, ret, "could not unmap file %s", file_handle->name);
}
/*
* __posix_map_file --
* Map the virtual address region backed by a file into our address space. This is a "best
* effort" attempt. If mmap fails for any reason, we silently mark the file as not mappable and
* use system calls for it from then on. We do not report the error to the caller: the failure
* to mmap is not a show stopper, it is simply a lost performance-enhancement opportunity.
*/
static void
__posix_map_file(WT_FILE_HANDLE *file_handle, WT_SESSION *wt_session)
{
WT_FILE_HANDLE_POSIX *pfh;
WT_SESSION_IMPL *session;
wt_off_t file_size;
void *previous_address;
session = (WT_SESSION_IMPL *)wt_session;
pfh = (WT_FILE_HANDLE_POSIX *)file_handle;
WT_ASSERT(session, pfh->mmap_file_mappable);
if (__posix_file_size((WT_FILE_HANDLE *)pfh, wt_session, &file_size) != 0) {
__wt_err(session, __wt_errno(), "%s: __posix_file_size", file_handle->name);
pfh->mmap_file_mappable = false;
return;
}
if (file_size <= 0) {
if (pfh->mmap_buf != NULL)
__posix_unmap_file(file_handle, wt_session);
return;
}
/* If the buffer was previously mapped, try to remap it to the same address */
previous_address = pfh->mmap_buf;
if ((pfh->mmap_buf = (uint8_t *)mmap(previous_address, (size_t)file_size, pfh->mmap_prot,
MAP_SHARED | MAP_FILE, pfh->fd, 0)) == MAP_FAILED) {
pfh->mmap_size = 0;
pfh->mmap_buf = NULL;
pfh->mmap_file_mappable = false;
__wt_err(
session, errno, "Could not mmap file %s. Will use system calls.", file_handle->name);
return;
}
pfh->mmap_size = file_size;
__wt_verbose(session, WT_VERB_FILEOPS,
"%s: file-mmap: fd=%d, size=%" PRId64 ", mapped buffer=%p", file_handle->name, pfh->fd,
pfh->mmap_size, (void *)pfh->mmap_buf);
}
/*
* __posix_sync --
* Underlying support function to flush a file descriptor. Fsync calls (or fsync-style calls,
* for example, fdatasync) are not retried on failure, and failure halts the system. Excerpted
* from the LWN.net article https://lwn.net/Articles/752063/: In short, PostgreSQL assumes that
* a successful call to fsync() indicates that all data written since the last successful call
* made it safely to persistent storage. But that is not what the kernel actually does. When a
* buffered I/O write fails due to a hardware-level error, filesystems will respond differently,
* but that behavior usually includes discarding the data in the affected pages and marking them
* as being clean. So a read of the blocks that were just written will likely return something
* other than the data that was written. Given the shared history of UNIX filesystems, and the
* difficulty of knowing what specific error will be returned under specific circumstances, we
* don't retry fsync-style calls and panic if a flush operation fails.
*/
static int
__posix_sync(WT_SESSION_IMPL *session, int fd, const char *name, const char *func)
{
WT_DECL_RET;
#if defined(F_FULLFSYNC)
/*
* OS X fsync documentation: "Note that while fsync() will flush all data from the host to the
* drive (i.e. the "permanent storage device"), the drive itself may not physically write the
* data to the platters for quite some time and it may be written in an out-of-order sequence.
* For applications that require tighter guarantees about the integrity of their data, Mac OS X
* provides the F_FULLFSYNC fcntl. The F_FULLFSYNC fcntl asks the drive to flush all buffered
* data to permanent storage."
*
* OS X F_FULLFSYNC fcntl documentation: "This is currently implemented on HFS, MS-DOS (FAT),
* and Universal Disk Format (UDF) file systems."
*
* See comment in __posix_sync(): sync cannot be retried or fail.
*/
static enum { FF_NOTSET, FF_IGNORE, FF_OK } ff_status = FF_NOTSET;
switch (ff_status) {
case FF_NOTSET:
WT_SYSCALL(fcntl(fd, F_FULLFSYNC, 0) == -1 ? -1 : 0, ret);
if (ret == 0) {
ff_status = FF_OK;
return (0);
}
/*
* If the first F_FULLFSYNC fails, assume the file system doesn't support it and fallback to
* fdatasync or fsync.
*/
ff_status = FF_IGNORE;
__wt_err(session, ret, "fcntl(F_FULLFSYNC) failed, falling back to fdatasync or fsync");
break;
case FF_IGNORE:
break;
case FF_OK:
WT_SYSCALL(fcntl(fd, F_FULLFSYNC, 0) == -1 ? -1 : 0, ret);
if (ret == 0)
return (0);
WT_RET_PANIC(session, ret, "%s: %s: fcntl(F_FULLFSYNC)", name, func);
}
#endif
/*
* Use fsync in case we run on BSD systems that don't flush file size changes as part of fdatasync.
* This is for extra safety and is not a guarantee that we are providing full support for these
* systems and/or other non POSIX 1003.1 Unix systems.
*/
#if defined(HAVE_FDATASYNC) && !defined(BSD)
/* See comment in __posix_sync(): sync cannot be retried or fail. */
WT_SYSCALL(fdatasync(fd), ret);
if (ret == 0)
return (0);
WT_RET_PANIC(session, ret, "%s: %s: fdatasync", name, func);
#else
/* See comment in __posix_sync(): sync cannot be retried or fail. */
WT_SYSCALL(fsync(fd), ret);
if (ret == 0)
return (0);
WT_RET_PANIC(session, ret, "%s: %s: fsync", name, func);
#endif
}
#ifdef __linux__
/*
* __posix_directory_sync --
* Flush a directory to ensure file creation, remove or rename is durable.
*/
static int
__posix_directory_sync(WT_SESSION_IMPL *session, const char *path)
{
WT_DECL_ITEM(tmp);
WT_DECL_RET;
int fd, tret;
char *dir, *dpos;
WT_RET(__wt_scr_alloc(session, 0, &tmp));
WT_ERR(__wt_buf_setstr(session, tmp, path));
/*
* This layer should never see a path that doesn't include a path separator. This code asserts
* that fact, and truncates the non-directory part of the path so dir ends with a '/'.
*/
dir = tmp->mem;
dpos = strrchr(dir, '/');
WT_ASSERT_ALWAYS(session, dpos != NULL, "Path doesn't include a directory: %s", dir);
dpos[1] = '\0';
fd = 0; /* -Wconditional-uninitialized */
WT_SYSCALL_RETRY(((fd = open(dir, O_RDONLY | O_CLOEXEC, 0444)) == -1 ? -1 : 0), ret);
if (ret != 0)
WT_ERR_MSG(session, ret, "%s: directory-sync: open", dir);
ret = __posix_sync(session, fd, dir, "directory-sync");
WT_SYSCALL(close(fd), tret);
if (tret != 0) {
__wt_err(session, tret, "%s: directory-sync: close", dir);
WT_TRET(tret);
}
err:
__wt_scr_free(session, &tmp);
if (ret == 0)
return (ret);
/* See comment in __posix_sync(): sync cannot be retried or fail. */
WT_RET_PANIC(session, ret, "%s: directory-sync", path);
}
#endif
/*
* __posix_fs_exist --
* Return if the file exists.
*/
static int
__posix_fs_exist(
WT_FILE_SYSTEM *file_system, WT_SESSION *wt_session, const char *name, bool *existp)
{
struct stat sb;
WT_DECL_RET;
WT_SESSION_IMPL *session;
WT_UNUSED(file_system);
session = (WT_SESSION_IMPL *)wt_session;
WT_SYSCALL(stat(name, &sb), ret);
if (ret == 0) {
*existp = true;
return (0);
}
if (ret == ENOENT) {
*existp = false;
return (0);
}
WT_RET_MSG(session, ret, "%s: file-exist: stat", name);
}
/*
* __posix_fs_remove --
* Remove a file.
*/
static int
__posix_fs_remove(
WT_FILE_SYSTEM *file_system, WT_SESSION *wt_session, const char *name, uint32_t flags)
{
WT_DECL_RET;
WT_SESSION_IMPL *session;
WT_UNUSED(file_system);
session = (WT_SESSION_IMPL *)wt_session;
/*
* ISO C doesn't require remove return -1 on failure or set errno (note POSIX 1003.1 extends C
* with those requirements). Regardless, use the unlink system call, instead of remove, to
* simplify error handling; where we're not doing any special checking for standards compliance,
* using unlink may be marginally safer.
*/
WT_SYSCALL(unlink(name), ret);
if (ret != 0)
WT_RET_MSG(session, ret, "%s: file-remove: unlink", name);
if (!LF_ISSET(WT_FS_DURABLE))
return (0);
#ifdef __linux__
/* Flush the backing directory to guarantee the remove. */
WT_RET(__wt_log_printf(session, "REMOVE: posix_directory_sync %s", name));
WT_RET(__posix_directory_sync(session, name));
WT_RET(__wt_log_printf(session, "REMOVE: DONE posix_directory_sync %s", name));
#endif
return (0);
}
/*
* __posix_fs_rename --
* Rename a file.
*/
static int
__posix_fs_rename(WT_FILE_SYSTEM *file_system, WT_SESSION *wt_session, const char *from,
const char *to, uint32_t flags)
{
WT_DECL_RET;
WT_SESSION_IMPL *session;
WT_UNUSED(file_system);
session = (WT_SESSION_IMPL *)wt_session;
/*
* ISO C doesn't require rename return -1 on failure or set errno (note POSIX 1003.1 extends C
* with those requirements). Be cautious, force any non-zero return to -1 so we'll check errno.
* We can still end up with the wrong errno (if errno is garbage), or the generic WT_ERROR
* return (if errno is 0), but we've done the best we can.
*/
WT_SYSCALL(rename(from, to) != 0 ? -1 : 0, ret);
if (ret != 0)
WT_RET_MSG(session, ret, "%s to %s: file-rename: rename", from, to);
if (!LF_ISSET(WT_FS_DURABLE))
return (0);
#ifdef __linux__
/*
* Flush the backing directory to guarantee the rename. My reading of POSIX 1003.1 is there's no
* guarantee flushing only one of the from or to directories, or flushing a common parent, is
* sufficient, and even if POSIX were to make that guarantee, existing filesystems are known to
* not provide the guarantee or only provide the guarantee with specific mount options. Flush
* both of the from/to directories until it's a performance problem.
*/
WT_RET(__wt_log_printf(session, "RENAME: posix_directory_sync %s", from));
WT_RET(__posix_directory_sync(session, from));
WT_RET(__wt_log_printf(session, "RENAME: DONE posix_directory_sync %s", from));
/*
* In almost all cases, we're going to be renaming files in the same directory, we can at least
* fast-path that.
*/
{
bool same_directory;
const char *fp, *tp;
fp = strrchr(from, '/');
tp = strrchr(to, '/');
same_directory = (fp == NULL && tp == NULL) ||
(fp != NULL && tp != NULL && fp - from == tp - to &&
memcmp(from, to, (size_t)(fp - from)) == 0);
if (!same_directory)
WT_RET(__posix_directory_sync(session, to));
}
#endif
return (0);
}
/*
* __posix_fs_size --
* Get the size of a file in bytes, by file name.
*/
static int
__posix_fs_size(
WT_FILE_SYSTEM *file_system, WT_SESSION *wt_session, const char *name, wt_off_t *sizep)
{
struct stat sb;
WT_DECL_RET;
WT_SESSION_IMPL *session;
WT_UNUSED(file_system);
session = (WT_SESSION_IMPL *)wt_session;
WT_SYSCALL(stat(name, &sb), ret);
if (ret == 0) {
*sizep = sb.st_size;
return (0);
}
WT_RET_MSG(session, ret, "%s: file-size: stat", name);
}
#if defined(HAVE_POSIX_FADVISE)
/*
* __posix_file_advise --
* POSIX fadvise.
*/
static int
__posix_file_advise(
WT_FILE_HANDLE *file_handle, WT_SESSION *wt_session, wt_off_t offset, wt_off_t len, int advice)
{
WT_DECL_RET;
WT_FILE_HANDLE_POSIX *pfh;
WT_SESSION_IMPL *session;
session = (WT_SESSION_IMPL *)wt_session;
pfh = (WT_FILE_HANDLE_POSIX *)file_handle;
WT_SYSCALL(posix_fadvise(pfh->fd, offset, len, advice), ret);
if (ret == 0)
return (0);
/*
* Treat EINVAL as not-supported, some systems don't support some flags. Quietly fail, callers
* expect not-supported failures, and reset the handle method to prevent future calls.
*/
if (ret == EINVAL) {
file_handle->fh_advise = NULL;
return (__wt_set_return(session, ENOTSUP));
}
WT_RET_MSG(session, ret, "%s: handle-advise: posix_fadvise", file_handle->name);
}
#endif
/*
* __posix_file_close --
* ANSI C close.
*/
static int
__posix_file_close(WT_FILE_HANDLE *file_handle, WT_SESSION *wt_session)
{
WT_DECL_RET;
WT_FILE_HANDLE_POSIX *pfh;
WT_SESSION_IMPL *session;
session = (WT_SESSION_IMPL *)wt_session;
pfh = (WT_FILE_HANDLE_POSIX *)file_handle;
__wt_verbose(session, WT_VERB_FILEOPS, "%s, file-close: fd=%d", file_handle->name, pfh->fd);
if (pfh->mmap_buf != NULL)
__posix_unmap_file(file_handle, wt_session);
/* Close the file handle. */
if (pfh->fd != -1) {
WT_SYSCALL(close(pfh->fd), ret);
if (ret != 0)
__wt_err(session, ret, "%s: handle-close: close", file_handle->name);
}
__wt_free(session, file_handle->name);
__wt_free(session, pfh);
return (ret);
}
/*
* __posix_file_lock --
* Lock/unlock a file.
*/
static int
__posix_file_lock(WT_FILE_HANDLE *file_handle, WT_SESSION *wt_session, bool lock)
{
struct flock fl;
WT_DECL_RET;
WT_FILE_HANDLE_POSIX *pfh;
WT_SESSION_IMPL *session;
session = (WT_SESSION_IMPL *)wt_session;
pfh = (WT_FILE_HANDLE_POSIX *)file_handle;
/*
* WiredTiger requires this function be able to acquire locks past the end of file.
*
* Note we're using fcntl(2) locking: all fcntl locks associated with a file for a given process
* are removed when any file descriptor for the file is closed by the process, even if a lock
* was never requested for that file descriptor.
*/
fl.l_start = 0;
fl.l_len = 1;
fl.l_type = lock ? F_WRLCK : F_UNLCK;
fl.l_whence = SEEK_SET;
WT_SYSCALL(fcntl(pfh->fd, F_SETLK, &fl) == -1 ? -1 : 0, ret);
if (ret == 0)
return (0);
WT_RET_MSG(session, ret, "%s: handle-lock: fcntl", file_handle->name);
}
/*
* __posix_file_read --
* POSIX pread.
*/
static int
__posix_file_read(
WT_FILE_HANDLE *file_handle, WT_SESSION *wt_session, wt_off_t offset, size_t len, void *buf)
{
WT_DECL_RET;
WT_FILE_HANDLE_POSIX *pfh;
WT_SESSION_IMPL *session;
size_t chunk;
ssize_t nr;
uint8_t *addr;
session = (WT_SESSION_IMPL *)wt_session;
pfh = (WT_FILE_HANDLE_POSIX *)file_handle;
__wt_verbose_debug2(session, WT_VERB_READ,
"read: %s, fd=%d, offset=%" PRId64 ", len=%" WT_SIZET_FMT, file_handle->name, pfh->fd, offset,
len);
/* Break reads larger than 1GB into 1GB chunks. */
nr = 0;
for (addr = buf; len > 0; addr += nr, len -= (size_t)nr, offset += nr) {
chunk = WT_MIN(len, WT_GIGABYTE);
/*
* The WT_SYSCALL_RETRY macro expects 0 for success. pread returns > 0 when it successfully
* reads bytes, adjust the return value. pread returns 0 when its EOF and if that is reached
* it is unexpected as we know how much we are reading.
*/
WT_SYSCALL_RETRY((nr = pread(pfh->fd, addr, chunk, offset)) <= 0 ? -1 : 0, ret);
if (ret != 0)
WT_RET_MSG(session, nr == 0 ? WT_ERROR : ret,
"%s: handle-read: pread: failed to read %" WT_SIZET_FMT " bytes at offset %" PRIuMAX,
file_handle->name, chunk, (uintmax_t)offset);
}
WT_STAT_CONN_INCRV(session, block_byte_read_syscall, len);
return (0);
}
/*
* __posix_file_read_mmap --
* Get the buffer from the mapped region.
*/
static int
__posix_file_read_mmap(
WT_FILE_HANDLE *file_handle, WT_SESSION *wt_session, wt_off_t offset, size_t len, void *buf)
{
WT_FILE_HANDLE_POSIX *pfh;
WT_SESSION_IMPL *session;
bool mmap_success;
session = (WT_SESSION_IMPL *)wt_session;
pfh = (WT_FILE_HANDLE_POSIX *)file_handle;
if (pfh->mmap_buf == NULL || pfh->mmap_resizing)
goto use_syscall;
__wt_verbose_debug2(session, WT_VERB_READ,
"read-mmap: %s, fd=%d, offset=%" PRId64 ", len=%" WT_SIZET_FMT
", mapped buffer: %p, mapped size = %" PRId64,
file_handle->name, pfh->fd, offset, len, (void *)pfh->mmap_buf, pfh->mmap_size);
/* Indicate that we might be using the mapped area */
(void)__wt_atomic_addv32(&pfh->mmap_usecount, 1);
/* Check after incrementing use count if we raced a resizing thread. */
if (pfh->mmap_resizing) {
(void)__wt_atomic_subv32(&pfh->mmap_usecount, 1);
goto use_syscall;
}
/*
* If the I/O falls inside the mapped buffer, and the buffer is not being re-sized, we will use
* the mapped buffer.
*/
mmap_success = false;
if (pfh->mmap_buf != NULL && pfh->mmap_size >= offset + (wt_off_t)len && !pfh->mmap_resizing) {
memcpy(buf, (void *)(pfh->mmap_buf + offset), len);
mmap_success = true;
WT_STAT_CONN_INCRV(session, block_byte_read_mmap, len);
}
/* Signal that we are done using the mapped buffer. */
(void)__wt_atomic_subv32(&pfh->mmap_usecount, 1);
if (mmap_success)
return (0);
use_syscall:
/* We couldn't use mmap for some reason, so use the system call. */
return (__posix_file_read(file_handle, wt_session, offset, len, buf));
}
/*
* __posix_file_sync --
* POSIX fsync.
*/
static int
__posix_file_sync(WT_FILE_HANDLE *file_handle, WT_SESSION *wt_session)
{
WT_FILE_HANDLE_POSIX *pfh;
WT_SESSION_IMPL *session;
session = (WT_SESSION_IMPL *)wt_session;
pfh = (WT_FILE_HANDLE_POSIX *)file_handle;
return (__posix_sync(session, pfh->fd, file_handle->name, "handle-sync"));
}
#ifdef HAVE_SYNC_FILE_RANGE
/*
* __posix_file_sync_nowait --
* POSIX fsync.
*/
static int
__posix_file_sync_nowait(WT_FILE_HANDLE *file_handle, WT_SESSION *wt_session)
{
WT_DECL_RET;
WT_FILE_HANDLE_POSIX *pfh;
WT_SESSION_IMPL *session;
session = (WT_SESSION_IMPL *)wt_session;
pfh = (WT_FILE_HANDLE_POSIX *)file_handle;
/* See comment in __posix_sync(): sync cannot be retried or fail. */
WT_SYSCALL(sync_file_range(pfh->fd, (off64_t)0, (off64_t)0, SYNC_FILE_RANGE_WRITE), ret);
if (ret == 0)
return (0);
WT_RET_PANIC(session, ret, "%s: handle-sync-nowait: sync_file_range", file_handle->name);
}
#endif
/*
* __posix_file_truncate --
* POSIX ftruncate.
*/
static int
__posix_file_truncate(WT_FILE_HANDLE *file_handle, WT_SESSION *wt_session, wt_off_t len)
{
WT_DECL_RET;
WT_FILE_HANDLE_POSIX *pfh;
WT_SESSION_IMPL *session;
bool remap;
session = (WT_SESSION_IMPL *)wt_session;
pfh = (WT_FILE_HANDLE_POSIX *)file_handle;
__wt_verbose_debug2(session, WT_VERB_FILEOPS,
"%s, file-truncate: size=%" PRId64 ", mapped size=%" PRId64, file_handle->name, len,
pfh->mmap_size);
/* Always call prepare. It will return whether a remap is needed or not. */
__wti_posix_prepare_remap_resize_file(file_handle, wt_session, len, &remap);
WT_SYSCALL_RETRY(ftruncate(pfh->fd, len), ret);
if (remap) {
if (ret == 0)
__wti_posix_remap_resize_file(file_handle, wt_session);
else {
__wti_posix_release_without_remap(file_handle);
WT_RET_MSG(session, ret, "%s: handle-truncate: ftruncate", file_handle->name);
}
}
return (ret);
}
/*
* __posix_file_write --
* POSIX pwrite.
*/
static int
__posix_file_write(
WT_FILE_HANDLE *file_handle, WT_SESSION *wt_session, wt_off_t offset, size_t len, const void *buf)
{
WT_FILE_HANDLE_POSIX *pfh;
WT_SESSION_IMPL *session;
size_t chunk;
ssize_t nw;
const uint8_t *addr;
session = (WT_SESSION_IMPL *)wt_session;
pfh = (WT_FILE_HANDLE_POSIX *)file_handle;
__wt_verbose_debug2(session, WT_VERB_WRITE,
"write: %s, fd=%d, offset=%" PRId64 ", len=%" WT_SIZET_FMT, file_handle->name, pfh->fd,
offset, len);
/* Break writes larger than 1GB into 1GB chunks. */
for (addr = buf; len > 0; addr += nw, len -= (size_t)nw, offset += nw) {
chunk = WT_MIN(len, WT_GIGABYTE);
if ((nw = pwrite(pfh->fd, addr, chunk, offset)) < 0)
WT_RET_MSG(session, __wt_errno(),
"%s: handle-write: pwrite: failed to write %" WT_SIZET_FMT
" bytes at offset %" PRIuMAX,
file_handle->name, chunk, (uintmax_t)offset);
}
WT_STAT_CONN_INCRV(session, block_byte_write_syscall, len);
return (0);
}
/*
* __posix_file_write_mmap --
* Write the buffer into the mapped region.
*/
static int
__posix_file_write_mmap(
WT_FILE_HANDLE *file_handle, WT_SESSION *wt_session, wt_off_t offset, size_t len, const void *buf)
{
static int remap_opportunities;
WT_FILE_HANDLE_POSIX *pfh;
WT_SESSION_IMPL *session;
bool mmap_success, remap;
session = (WT_SESSION_IMPL *)wt_session;
pfh = (WT_FILE_HANDLE_POSIX *)file_handle;
__wt_verbose_debug2(session, WT_VERB_WRITE,
"write-mmap: %s, fd=%d, offset=%" PRId64 ", len=%" WT_SIZET_FMT
", mapped buffer: %p, mapped size = %" PRId64,
file_handle->name, pfh->fd, offset, len, (void *)pfh->mmap_buf, pfh->mmap_size);
if (pfh->mmap_buf == NULL || pfh->mmap_resizing)
goto use_syscall;
/* Indicate that we might be using the mapped area */
(void)__wt_atomic_addv32(&pfh->mmap_usecount, 1);
/* Check after incrementing use count if we raced a resizing thread. */
if (pfh->mmap_resizing) {
(void)__wt_atomic_subv32(&pfh->mmap_usecount, 1);
goto use_syscall;
}
/*
* If the I/O falls inside the mapped buffer, and the buffer is not being re-sized, we will use
* the mapped buffer.
*/
mmap_success = false;
if (pfh->mmap_buf != NULL && pfh->mmap_size >= offset + (wt_off_t)len && !pfh->mmap_resizing) {
memcpy((void *)(pfh->mmap_buf + offset), buf, len);
mmap_success = true;
WT_STAT_CONN_INCRV(session, block_byte_write_mmap, len);
}
/* Signal that we are done using the mapped buffer. */
(void)__wt_atomic_subv32(&pfh->mmap_usecount, 1);
if (mmap_success)
return (0);
use_syscall:
/* We couldn't use mmap for some reason, so use the system call. */
WT_RET(__posix_file_write(file_handle, wt_session, offset, len, buf));
/*
* If we wrote the file via a system call, we might have extended its size. If the file is mapped,
* remap it with the new size. If we are actively extending the file, don't remap it on every write
* to avoid overhead.
*/
#define WT_REMAP_SKIP 10
if (pfh->mmap_buf != NULL && !pfh->mmap_resizing && pfh->mmap_size < offset + (wt_off_t)len)
/* If we are actively extending the file, don't remap it on every write. */
if ((remap_opportunities++) % WT_REMAP_SKIP == 0) {
__wti_posix_prepare_remap_resize_file(
file_handle, wt_session, offset + (wt_off_t)len, &remap);
if (remap)
__wti_posix_remap_resize_file(file_handle, wt_session);
WT_STAT_CONN_INCRV(session, block_remap_file_write, 1);
}
return (0);
}
/*
* __posix_open_file_cloexec --
* Prevent child access to file handles.
*/
static WT_INLINE int
__posix_open_file_cloexec(WT_SESSION_IMPL *session, int fd, const char *name)
{
#if defined(FD_CLOEXEC) && !defined(O_CLOEXEC)
int f;
/*
* Security: The application may spawn a new process, and we don't want another process to have
* access to our file handles. There's an obvious race between the open and this call, prefer
* the flag to open if available.
*/
if ((f = fcntl(fd, F_GETFD)) == -1 || fcntl(fd, F_SETFD, f | FD_CLOEXEC) == -1)
WT_RET_MSG(session, __wt_errno(), "%s: handle-open: fcntl(FD_CLOEXEC)", name);
return (0);
#else
WT_UNUSED(session);
WT_UNUSED(fd);
WT_UNUSED(name);
return (0);
#endif
}
/*
* __posix_open_file --
* Open a file handle.
*/
static int
__posix_open_file(WT_FILE_SYSTEM *file_system, WT_SESSION *wt_session, const char *name,
WT_FS_OPEN_FILE_TYPE file_type, uint32_t flags, WT_FILE_HANDLE **file_handlep)
{
WT_CONNECTION_IMPL *conn;
WT_DECL_RET;
WT_FILE_HANDLE *file_handle;
WT_FILE_HANDLE_POSIX *pfh;
WT_LOG_MANAGER *log_mgr;
WT_SESSION_IMPL *session;
mode_t mode;
int advise_flag, f;
WT_UNUSED(file_system);
file_handle = NULL;
*file_handlep = NULL;
session = (WT_SESSION_IMPL *)wt_session;
conn = S2C(session);
log_mgr = &conn->log_mgr;
WT_RET(__wt_calloc_one(session, &pfh));
/* Set up error handling. */
pfh->fd = -1;
if (file_type == WT_FS_OPEN_FILE_TYPE_DIRECTORY) {
f = O_RDONLY;
#ifdef O_CLOEXEC
/*
* Security: The application may spawn a new process, and we don't want another process to
* have access to our file handles.
*/
f |= O_CLOEXEC;
#endif
WT_SYSCALL_RETRY(((pfh->fd = open(name, f, 0444)) == -1 ? -1 : 0), ret);
if (ret != 0)
WT_ERR_MSG(session, ret, "%s: handle-open: open-directory", name);
WT_ERR(__posix_open_file_cloexec(session, pfh->fd, name));
goto directory_open;
}
f = LF_ISSET(WT_FS_OPEN_READONLY) ? O_RDONLY : O_RDWR;
if (LF_ISSET(WT_FS_OPEN_CREATE)) {
f |= O_CREAT;
if (LF_ISSET(WT_FS_OPEN_EXCLUSIVE))
f |= O_EXCL;
mode = 0666;
} else
mode = 0;
#ifdef O_BINARY
/* Windows clones: we always want to treat the file as a binary. */
f |= O_BINARY;
#endif
#ifdef O_CLOEXEC
/*
* Security: The application may spawn a new process, and we don't want another process to have
* access to our file handles.
*/
f |= O_CLOEXEC;
#endif
#ifdef O_NOATIME
/* Avoid updating metadata for read-only workloads. */
if (file_type == WT_FS_OPEN_FILE_TYPE_DATA)
f |= O_NOATIME;
#endif
if (file_type == WT_FS_OPEN_FILE_TYPE_LOG && FLD_ISSET(log_mgr->txn_logsync, WT_LOG_DSYNC)) {
#ifdef O_DSYNC
f |= O_DSYNC;
#elif defined(O_SYNC)
f |= O_SYNC;
#else
WT_ERR_MSG(session, ENOTSUP, "unsupported log sync mode configured");
#endif
}
/* Create/Open the file. */
WT_SYSCALL_RETRY(((pfh->fd = open(name, f, mode)) == -1 ? -1 : 0), ret);
if (ret != 0)
WT_ERR_MSG(session, ret, "%s: handle-open: open", name);
#ifdef __linux__
/*
* Durability: some filesystems require a directory sync to be confident the file will appear.
*/
if (LF_ISSET(WT_FS_OPEN_DURABLE)) {
WT_ERR(__wt_log_printf(session, "OPEN/CREATE: posix_directory_sync %s", name));
WT_ERR(__posix_directory_sync(session, name));
WT_ERR(__wt_log_printf(session, "OPEN/CREATE: DONE posix_directory_sync %s", name));
}
#endif
WT_ERR(__posix_open_file_cloexec(session, pfh->fd, name));
#if defined(HAVE_POSIX_FADVISE)
/*
* If the user set an access pattern hint, call fadvise now. Ignore fadvise when doing direct
* I/O, the kernel cache isn't interesting.
*/
if (file_type == WT_FS_OPEN_FILE_TYPE_DATA &&
LF_ISSET(WT_FS_OPEN_ACCESS_RAND | WT_FS_OPEN_ACCESS_SEQ)) {
advise_flag = 0;
if (LF_ISSET(WT_FS_OPEN_ACCESS_RAND))
advise_flag = POSIX_FADV_RANDOM;
if (LF_ISSET(WT_FS_OPEN_ACCESS_SEQ))
advise_flag = POSIX_FADV_SEQUENTIAL;
WT_SYSCALL(posix_fadvise(pfh->fd, 0, 0, advise_flag), ret);
if (ret != 0)
WT_ERR_MSG(session, ret, "%s: handle-open: posix_fadvise", name);
}
#else
WT_UNUSED(advise_flag);
#endif
directory_open:
/* Initialize public information. */
file_handle = (WT_FILE_HANDLE *)pfh;
WT_ERR(__wt_strdup(session, name, &file_handle->name));
pfh->mmap_prot = LF_ISSET(WT_FS_OPEN_READONLY) ? PROT_READ : PROT_READ | PROT_WRITE;
pfh->mmap_flags = LF_ISSET(WT_FS_OPEN_READONLY) ? MAP_PRIVATE : MAP_SHARED;
if (LF_ISSET(WT_FS_OPEN_FORCE_MMAP))
pfh->mmap_file_mappable = true;
if (conn->mmap_all) {
/*
* We are going to use mmap for I/O. So let's mmap the file on opening. If mmap fails, we
* will just mark the file as not mappable (inside the mapping function) and will use system
* calls for I/O on this file. We will not crash the database if mmap fails.
*/
if (file_type == WT_FS_OPEN_FILE_TYPE_DATA || file_type == WT_FS_OPEN_FILE_TYPE_LOG) {
pfh->mmap_file_mappable = true;
__posix_map_file(file_handle, wt_session);
}
}
file_handle->close = __posix_file_close;
#if defined(HAVE_POSIX_FADVISE)
file_handle->fh_advise = __posix_file_advise;
#endif
file_handle->fh_extend = __wti_posix_file_extend;
file_handle->fh_lock = __posix_file_lock;
#ifdef WORDS_BIGENDIAN
/*
* The underlying objects are little-endian, mapping objects isn't currently supported on big-endian
* systems.
*/
#else
file_handle->fh_map = __wti_posix_map;
#ifdef HAVE_POSIX_MADVISE
file_handle->fh_map_discard = __wti_posix_map_discard;
file_handle->fh_map_preload = __wti_posix_map_preload;
#endif
file_handle->fh_unmap = __wti_posix_unmap;
#endif
if (pfh->mmap_file_mappable)
file_handle->fh_read = __posix_file_read_mmap;
else
file_handle->fh_read = __posix_file_read;
file_handle->fh_size = __posix_file_size;
file_handle->fh_sync = __posix_file_sync;
#ifdef HAVE_SYNC_FILE_RANGE
file_handle->fh_sync_nowait = __posix_file_sync_nowait;
#endif
file_handle->fh_truncate = __posix_file_truncate;
if (pfh->mmap_file_mappable)
file_handle->fh_write = __posix_file_write_mmap;
else
file_handle->fh_write = __posix_file_write;
*file_handlep = file_handle;
return (0);
err:
WT_TRET(__posix_file_close((WT_FILE_HANDLE *)pfh, wt_session));
return (ret);
}
/*
* __posix_terminate --
* Terminate a POSIX configuration.
*/
static int
__posix_terminate(WT_FILE_SYSTEM *file_system, WT_SESSION *wt_session)
{
WT_SESSION_IMPL *session;