fs_io.cc

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/*
 * Copyright (C) 1996-2025 The Squid Software Foundation and contributors
 *
 * Squid software is distributed under GPLv2+ license and includes
 * contributions from numerous individuals and organizations.
 * Please see the COPYING and CONTRIBUTORS files for details.
 */
 
/* DEBUG: section 06    Disk I/O Routines */
 
#include "squid.h"
#include "comm/Loops.h"
#include "compat/unistd.h"
#include "fd.h"
#include "fde.h"
#include "fs_io.h"
#include "globals.h"
#include "MemBuf.h"
#include "StatCounters.h"
 
#include <cerrno>
 
static PF diskHandleRead;
static PF diskHandleWrite;
 
#if _SQUID_WINDOWS_ || _SQUID_OS2_
static int
diskWriteIsComplete(int fd)
{
    return fd_table[fd].disk.write_q ? 0 : 1;
}
 
#endif
 
/* hack needed on SunStudio to avoid linkage convention mismatch */
static void cxx_xfree(void *ptr)
{
    xfree(ptr);
}
 
dwrite_q::dwrite_q(const size_t aSize, char * const aBuffer, FREE * const aFree):
    buf(aBuffer),
    capacity(aSize),
    free_func(aFree)
{
    assert(buf || !free_func);
    if (!buf) {
        buf = static_cast<char *>(xmalloc(aSize));
        free_func = cxx_xfree; // dwrite_q buffer xfree()
    } else {
        len = aSize;
    }
}
 
dwrite_q::~dwrite_q()
{
    if (free_func)
        free_func(buf);
}
 
/*
 * opens a disk file specified by 'path'.  This function always
 * blocks!  There is no callback.
 */
int
file_open(const char *path, int mode)
{
    if (FILE_MODE(mode) == O_WRONLY)
        mode |= O_APPEND;
 
    errno = 0;
 
    auto fd = xopen(path, mode, 0644);
 
    ++ statCounter.syscalls.disk.opens;
 
    if (fd < 0) {
        int xerrno = errno;
        debugs(50, 3, "error opening file " << path << ": " << xstrerr(xerrno));
        fd = DISK_ERROR;
    } else {
        debugs(6, 5, "FD " << fd);
        commSetCloseOnExec(fd);
        fd_open(fd, FD_FILE, path);
    }
 
    return fd;
}
 
/* close a disk file. */
void
file_close(int fd)
{
    fde *F = &fd_table[fd];
    PF *read_callback;
    assert(fd >= 0);
    assert(F->flags.open);
 
    if ((read_callback = F->read_handler)) {
        F->read_handler = nullptr;
        read_callback(-1, F->read_data);
    }
 
    if (F->flags.write_daemon) {
#if _SQUID_WINDOWS_ || _SQUID_OS2_
        /*
         * on some operating systems, you can not delete or rename
         * open files, so we won't allow delayed close.
         */
        while (!diskWriteIsComplete(fd))
            diskHandleWrite(fd, nullptr);
#else
        F->flags.close_request = true;
        debugs(6, 2, "file_close: FD " << fd << ", delaying close");
        return;
#endif
 
    }
 
    /*
     * Assert there is no write callback.  Otherwise we might be
     * leaking write state data by closing the descriptor
     */
    assert(F->write_handler == nullptr);
 
    xclose(fd);
 
    debugs(6, F->flags.close_request ? 2 : 5, "file_close: FD " << fd << " really closing");
 
    fd_close(fd);
 
    ++ statCounter.syscalls.disk.closes;
}
 
/*
 * This function has the purpose of combining multiple writes.  This is
 * to facilitate the ASYNC_IO option since it can only guarantee 1
 * write to a file per trip around the comm.c select() loop. That's bad
 * because more than 1 write can be made to the access.log file per
 * trip, and so this code is purely designed to help batch multiple
 * sequential writes to the access.log file.  Squid will never issue
 * multiple writes for any other file type during 1 trip around the
 * select() loop.       --SLF
 */
static void
diskCombineWrites(_fde_disk *fdd)
{
    /*
     * We need to combine multiple write requests on an FD's write
     * queue But only if we don't need to seek() in between them, ugh!
     * XXX This currently ignores any seeks (file_offset)
     */
 
    if (fdd->write_q != nullptr && fdd->write_q->next != nullptr) {
        size_t wantCapacity = 0;
 
        for (dwrite_q *q = fdd->write_q; q != nullptr; q = q->next)
            wantCapacity += q->len - q->buf_offset; // XXX: might overflow
 
        const auto wq = new dwrite_q(wantCapacity);
        while (const auto q = fdd->write_q) {
            const auto len = q->len - q->buf_offset;
            memcpy(wq->buf + wq->len, q->buf + q->buf_offset, len);
            wq->len += len;
            fdd->write_q = q->next;
            delete q;
        };
 
        fdd->write_q_tail = wq;
 
        fdd->write_q = wq;
    }
}
 
/* write handler */
static void
diskHandleWrite(int fd, void *)
{
    int len = 0;
    fde *F = &fd_table[fd];
 
    _fde_disk *fdd = &F->disk;
    int status = DISK_OK;
    bool do_close;
 
    if (!fdd->write_q)
        return;
 
    debugs(6, 3, "diskHandleWrite: FD " << fd);
 
    F->flags.write_daemon = false;
 
    assert(fdd->write_q != nullptr);
 
    assert(fdd->write_q->len > fdd->write_q->buf_offset);
 
    debugs(6, 3, "diskHandleWrite: FD " << fd << " writing " <<
           (fdd->write_q->len - fdd->write_q->buf_offset) << " bytes at " <<
           fdd->write_q->file_offset);
 
    errno = 0;
 
    if (fdd->write_q->file_offset != -1) {
        errno = 0;
        if (lseek(fd, fdd->write_q->file_offset, SEEK_SET) == -1) {
            int xerrno = errno;
            debugs(50, DBG_IMPORTANT, "ERROR: in seek for FD " << fd << ": " << xstrerr(xerrno));
            // XXX: handle error?
        }
    }
 
    len = FD_WRITE_METHOD(fd,
                          fdd->write_q->buf + fdd->write_q->buf_offset,
                          fdd->write_q->len - fdd->write_q->buf_offset);
    const auto xerrno = errno;
 
    debugs(6, 3, "diskHandleWrite: FD " << fd << " len = " << len);
 
    ++ statCounter.syscalls.disk.writes;
 
    fd_bytes(fd, len, IoDirection::Write);
 
    if (len < 0) {
        if (!ignoreErrno(xerrno)) {
            status = xerrno == ENOSPC ? DISK_NO_SPACE_LEFT : DISK_ERROR;
            debugs(50, DBG_IMPORTANT, "ERROR: diskHandleWrite: FD " << fd << ": disk write failure: " << xstrerr(xerrno));
 
            /*
             * If there is no write callback, then this file is
             * most likely something important like a log file, or
             * an interprocess pipe.  Its not a swapfile.  We feel
             * that a write failure on a log file is rather important,
             * and Squid doesn't otherwise deal with this condition.
             * So to get the administrators attention, we exit with
             * a fatal message.
             */
 
            if (fdd->wrt_handle == nullptr)
                fatal("Write failure -- check your disk space and cache.log");
 
            /*
             * If there is a write failure, then we notify the
             * upper layer via the callback, at the end of this
             * function.  Meanwhile, flush all pending buffers
             * here.  Let the upper layer decide how to handle the
             * failure.  This will prevent experiencing multiple,
             * repeated write failures for the same FD because of
             * the queued data.
             */
            while (const auto q = fdd->write_q) {
                fdd->write_q = q->next;
                delete q;
            }
        }
 
        len = 0;
    }
 
    if (const auto q = fdd->write_q) {
        /* q might become NULL from write failure above */
        q->buf_offset += len;
 
        if (q->buf_offset > q->len)
            debugs(50, DBG_IMPORTANT, "diskHandleWriteComplete: q->buf_offset > q->len (" <<
                   q << "," << (int) q->buf_offset << ", " << q->len << ", " <<
                   len << " FD " << fd << ")");
 
        assert(q->buf_offset <= q->len);
 
        if (q->buf_offset == q->len) {
            /* complete write */
            fdd->write_q = q->next;
            delete q;
        }
    }
 
    if (fdd->write_q == nullptr) {
        /* no more data */
        fdd->write_q_tail = nullptr;
    } else {
        /* another block is queued */
        diskCombineWrites(fdd);
        Comm::SetSelect(fd, COMM_SELECT_WRITE, diskHandleWrite, nullptr, 0);
        F->flags.write_daemon = true;
    }
 
    do_close = F->flags.close_request;
 
    if (fdd->wrt_handle) {
        DWCB *callback = fdd->wrt_handle;
        void *cbdata;
        fdd->wrt_handle = nullptr;
 
        if (cbdataReferenceValidDone(fdd->wrt_handle_data, &cbdata)) {
            callback(fd, status, len, cbdata);
            /*
             * NOTE, this callback can close the FD, so we must
             * not touch 'F', 'fdd', etc. after this.
             */
            return;
            /* XXX But what about close_request??? */
        }
    }
 
    if (do_close)
        file_close(fd);
}
 
/* write block to a file */
/* write back queue. Only one writer at a time. */
/* call a handle when writing is complete. */
void
file_write(int fd,
           off_t file_offset,
           void const *ptr_to_buf,
           int len,
           DWCB * handle,
           void *handle_data,
           FREE * free_func)
{
    fde *F = &fd_table[fd];
    assert(fd >= 0);
    assert(F->flags.open);
    /* if we got here. Caller is eligible to write. */
    const auto wq = new dwrite_q(len, static_cast<char *>(const_cast<void *>(ptr_to_buf)), free_func);
    wq->file_offset = file_offset;
 
    if (!F->disk.wrt_handle_data) {
        F->disk.wrt_handle = handle;
        F->disk.wrt_handle_data = cbdataReference(handle_data);
    } else {
        /* Detect if there is multiple concurrent users of this fd.. we only support one callback */
        assert(F->disk.wrt_handle_data == handle_data && F->disk.wrt_handle == handle);
    }
 
    /* add to queue */
    if (F->disk.write_q == nullptr) {
        /* empty queue */
        F->disk.write_q = F->disk.write_q_tail = wq;
    } else {
        F->disk.write_q_tail->next = wq;
        F->disk.write_q_tail = wq;
    }
 
    if (!F->flags.write_daemon) {
        diskHandleWrite(fd, nullptr);
    }
}
 
/* Read from FD */
static void
diskHandleRead(int fd, void *data)
{
    dread_ctrl *ctrl_dat = (dread_ctrl *)data;
    fde *F = &fd_table[fd];
    int len;
    int rc = DISK_OK;
    int xerrno;
 
    /*
     * FD < 0 indicates premature close; we just have to free
     * the state data.
     */
 
    if (fd < 0) {
        delete ctrl_dat;
        return;
    }
 
#if WRITES_MAINTAIN_DISK_OFFSET
    if (F->disk.offset != ctrl_dat->offset) {
#else
    {
#endif
        debugs(6, 3, "diskHandleRead: FD " << fd << " seeking to offset " << ctrl_dat->offset);
        errno = 0;
        if (lseek(fd, ctrl_dat->offset, SEEK_SET) == -1) {
            xerrno = errno;
            // shouldn't happen, let's detect that
            debugs(50, DBG_IMPORTANT, "ERROR: in seek for FD " << fd << ": " << xstrerr(xerrno));
            // XXX handle failures?
        }
        ++ statCounter.syscalls.disk.seeks;
        F->disk.offset = ctrl_dat->offset;
    }
 
    errno = 0;
    len = FD_READ_METHOD(fd, ctrl_dat->buf, ctrl_dat->req_len);
    xerrno = errno;
 
    if (len > 0)
        F->disk.offset += len;
 
    ++ statCounter.syscalls.disk.reads;
 
    fd_bytes(fd, len, IoDirection::Read);
 
    if (len < 0) {
        if (ignoreErrno(xerrno)) {
            Comm::SetSelect(fd, COMM_SELECT_READ, diskHandleRead, ctrl_dat, 0);
            return;
        }
 
        debugs(50, DBG_IMPORTANT, "diskHandleRead: FD " << fd << ": " << xstrerr(xerrno));
        len = 0;
        rc = DISK_ERROR;
    } else if (len == 0) {
        rc = DISK_EOF;
    }
 
    if (cbdataReferenceValid(ctrl_dat->client_data))
        ctrl_dat->handler(fd, ctrl_dat->buf, len, rc, ctrl_dat->client_data);
 
    cbdataReferenceDone(ctrl_dat->client_data);
 
    delete ctrl_dat;
}
 
/* start read operation */
/* buffer must be allocated from the caller.
 * It must have at least req_len space in there.
 * call handler when a reading is complete. */
void
file_read(int fd, char *buf, int req_len, off_t offset, DRCB * handler, void *client_data)
{
    assert(fd >= 0);
    const auto ctrl_dat = new dread_ctrl(fd, offset, buf, req_len, handler, cbdataReference(client_data));
    diskHandleRead(fd, ctrl_dat);
}
 
void
safeunlink(const char *s, int quiet)
{
    ++ statCounter.syscalls.disk.unlinks;
 
    if (unlink(s) < 0 && !quiet) {
        int xerrno = errno;
        debugs(50, DBG_IMPORTANT, "ERROR: safeunlink: Could not delete " << s << ": " << xstrerr(xerrno));
    }
}
 
bool
FileRename(const SBuf &from, const SBuf &to)
{
    debugs(21, 2, "renaming " << from << " to " << to);
 
    // non-const copy for c_str()
    SBuf from2(from);
    // ensure c_str() lifetimes even if `to` and `from` share memory
    SBuf to2(to.rawContent(), to.length());
 
#if _SQUID_OS2_ || _SQUID_WINDOWS_
    remove(to2.c_str());
#endif
 
    if (rename(from2.c_str(), to2.c_str()) == 0)
        return true;
 
    int xerrno = errno;
    debugs(21, (xerrno == ENOENT ? 2 : DBG_IMPORTANT), "ERROR: Cannot rename " << from << " to " << to << ": " << xstrerr(xerrno));
 
    return false;
}
 
int
fsBlockSize(const char *path, int *blksize)
{
    struct statvfs sfs;
 
    if (xstatvfs(path, &sfs)) {
        int xerrno = errno;
        debugs(50, DBG_IMPORTANT, "" << path << ": " << xstrerr(xerrno));
        *blksize = 2048;
        return 1;
    }
 
    *blksize = (int) sfs.f_frsize;
 
    // Sanity check; make sure we have a meaningful value.
    if (*blksize < 512)
        *blksize = 2048;
 
    return 0;
}
 
#define fsbtoblk(num, fsbs, bs) \
    (((fsbs) != 0 && (fsbs) < (bs)) ? \
            (num) / ((bs) / (fsbs)) : (num) * ((fsbs) / (bs)))
int
fsStats(const char *path, int *totl_kb, int *free_kb, int *totl_in, int *free_in)
{
    struct statvfs sfs;
 
    if (xstatvfs(path, &sfs)) {
        int xerrno = errno;
        debugs(50, DBG_IMPORTANT, "" << path << ": " << xstrerr(xerrno));
        return 1;
    }
 
    *totl_kb = (int) fsbtoblk(sfs.f_blocks, sfs.f_frsize, 1024);
    *free_kb = (int) fsbtoblk(sfs.f_bfree, sfs.f_frsize, 1024);
    *totl_in = (int) sfs.f_files;
    *free_in = (int) sfs.f_ffree;
    return 0;
}