src/xcalls/x_lseek.c

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#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <misc/debug.h>
#include <misc/errno.h>
#include <core/tx.h>
#include <core/config.h>
#include <core/koa.h>
#include <core/buffer.h>
#include <core/txdesc.h>
#include <core/stats.h>
#include <libc/syscalls.h>
#include <xcalls/xcalls.h>


typedef struct x_lseek_undo_args_s x_lseek_undo_args_t;

struct x_lseek_undo_args_s {
        int   fd;
        off_t old_position;
};


static
void
x_lseek_undo(void *args, int *result)
{
        x_lseek_undo_args_t *args_undo = (x_lseek_undo_args_t *) args;
        int                 local_result = 0;

        if (txc_libc_lseek(args_undo->fd, 
                           args_undo->old_position, SEEK_SET) < 0)
        {
                local_result = errno;
                goto done;
        }
done:
        if (result) {
                *result = local_result;
        }
}


off_t 
XCALL_DEF(x_lseek)(int fd, off_t offset, int whence, int *result)
{
        txc_tx_t            *txd;
        txc_koamgr_t        *koamgr = txc_g_koamgr;
        txc_koa_t           *koa;
        txc_sentinel_t      *sentinel;
        txc_result_t        xret;
        int                 ret;
        x_lseek_undo_args_t *args_undo;
        int                 local_result;


        txd = txc_tx_get_txd();

        switch(txc_tx_get_xactstate(txd)) {
                case TXC_XACTSTATE_TRANSACTIONAL_IRREVOCABLE:
                case TXC_XACTSTATE_NONTRANSACTIONAL:
                        if ((ret = txc_libc_lseek(fd, offset, whence)) < 0) {
                                local_result = errno;
                        } else {
                                local_result = 0;
                        }
                        goto done;

                case TXC_XACTSTATE_TRANSACTIONAL_RETRYABLE:
                        txc_koa_lock_fd(koamgr, fd);
                        xret = txc_koa_lookup_fd2koa(koamgr, fd, &koa);
                        if (xret == TXC_R_FAILURE) {
                                /* 
                                 * The KOA mapped to the file descriptor has gone. Report
                                 * this error as invalid file descriptor.
                                 */
                                txc_koa_unlock_fd(koamgr, fd);
                                local_result = EBADF;
                                ret = -1;
                                goto done;
                        }
                        sentinel = txc_koa_get_sentinel(koa);
                        xret = txc_sentinel_tryacquire(txd, sentinel, 
                                                       TXC_SENTINEL_ACQUIREONRETRY);
                        txc_koa_unlock_fd(koamgr, fd);
                        if (xret == TXC_R_BUSYSENTINEL) {
                                txc_tx_abort_transaction(txd, TXC_ABORTREASON_BUSYSENTINEL);
                                TXC_INTERNALERROR("Never gets here. Transaction abort failed.\n");
                        }

                        /* Got sentinel. Continue with the rest of the stuff. */

                        if ((args_undo = (x_lseek_undo_args_t *)
                                         txc_buffer_linear_malloc(txd->buffer_linear, 
                                                                  sizeof(x_lseek_undo_args_t)))
                             == NULL)
                        {       
                                local_result = ENOMEM;
                                ret = -1;
                                goto error_handler_0;
                        }
                        args_undo->fd = fd;

                        /* 
                         * If seek is relative to current file position then we can find
                         * out our current position using simple arithmetic. Otherwise we
                         * need a second lseek to get the current position.
                         */
                        if (whence == SEEK_CUR) {
                                if ((ret = txc_libc_lseek(fd, offset, whence)) < 0) {
                                        local_result = errno;
                                        goto error_handler_1;
                                }
                                args_undo->old_position = ret - offset;
                        } else {
                                args_undo->old_position = txc_libc_lseek(fd, 0, SEEK_CUR);
                                if ((ret = txc_libc_lseek(fd, offset, whence)) < 0) {
                                        local_result = errno;
                                        goto error_handler_1;
                                }
                        }
                        txc_tx_register_undo_action(txd, x_lseek_undo, 
                                                    (void *) args_undo, result,
                                                    TXC_TX_REGULAR_UNDO_ACTION_ORDER);
                        local_result = 0;
                        /* 
                         * ret was assigned offset location as measured in bytes from the 
                         * beginning of the file 
                         */
                        txc_stats_txstat_increment(txd, XCALL, x_lseek, 1);
                        goto done;

                default:
                        TXC_INTERNALERROR("Unknown transaction state\n");
        }

error_handler_1:
        txc_buffer_linear_free(txd->buffer_linear,
                                   sizeof(x_lseek_undo_args_t));
error_handler_0:
done:
        if (result) {
                *result = local_result;
        }
        return ret;
}

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