src/xcalls/x_open.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_open_undo_args_s x_open_undo_args_t;

struct x_open_undo_args_s {
        int       fd;
        txc_koa_t *koa;
};


static
void
x_open_undo(void *args, int *result)
{
        int                local_errno = 0; 
        x_open_undo_args_t *myargs = (x_open_undo_args_t *) args;
        txc_koamgr_t       *koamgr;

        koamgr = txc_koa_get_koamgr(myargs->koa);
        txc_koa_lock_alias_cache(koamgr);
        txc_koa_lock_fd(koamgr, myargs->fd);
        txc_koa_detach_fd(myargs->koa, myargs->fd, 0);
        if (txc_libc_close(myargs->fd) < 0) {
                local_errno = errno;
        }       
        txc_koa_unlock_fd(koamgr, myargs->fd);
        txc_koa_unlock_alias_cache(koamgr);
        if (result) {
                *result = local_errno;
        }
}


int
XCALL_DEF(x_open)(const char *pathname, int flags, mode_t mode, 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                fildes;
        int                ret;
        ino_t              inode;
        x_open_undo_args_t *args_undo; 
        int                open_flags = O_RDWR | flags;
        int                local_result = 0;

        txd = txc_tx_get_txd();

        switch(txc_tx_get_xactstate(txd)) {
                case TXC_XACTSTATE_TRANSACTIONAL_RETRYABLE:
                        /* Serialize open/create/close file operations to detect aliasing */
                        txc_koa_lock_alias_cache(koamgr);
                        txc_koa_path2inode(pathname, &inode);
                        if (inode == 0) {
                                /* File does not exist. */
                                txc_koa_unlock_alias_cache(koamgr);
                                local_result = EACCES;
                                ret = -1;
                                goto done;
                        } else {
                                if ((ret = fildes = txc_libc_open(pathname, open_flags, mode)) < 0) { 
                                        txc_koa_unlock_alias_cache(koamgr);
                                        local_result = errno;
                                        goto done;
                                }
                                if (txc_koa_alias_cache_lookup_inode(koamgr, inode, &koa) 
                                    == TXC_R_SUCCESS) 
                                {
                                        /* 
                                         * CASE 1:
                                         *  - KOA exists in the alias cache so other in-flight 
                                         *    transaction may operate on the file.
                                         */
                                        txc_koa_lock_fds_refby_koa(koa);
                                        txc_koa_lock_fd(koamgr, fildes);
                                        txc_koa_attach_fd(koa, fildes, 0);
                                        sentinel = txc_koa_get_sentinel(koa);
                                        xret = txc_sentinel_tryacquire(txd, sentinel, 0);
                                        if (xret == TXC_R_BUSYSENTINEL) {
                                                txc_libc_close(fildes);
                                                txc_koa_detach_fd(koa, fildes, 0);
                                                /* 
                                                 * Explicitly release the lock on fildes because we 
                                                 * have detached it from the KOA.
                                                 */
                                                txc_koa_unlock_fd(koamgr, fildes);
                                                txc_koa_unlock_fds_refby_koa(koa);
                                                txc_koa_unlock_alias_cache(koamgr);
                                                txc_tx_abort_transaction(txd, TXC_ABORTREASON_BUSYSENTINEL);
                                                TXC_INTERNALERROR("Never gets here. Transaction abort failed.\n");
                                        }

                                        args_undo = (x_open_undo_args_t *)
                                                    txc_buffer_linear_malloc(txd->buffer_linear, 
                                                                             sizeof(x_open_undo_args_t));
                                        if (args_undo == NULL) {
                                                TXC_INTERNALERROR("Allocation failed. Linear buffer out of space.\n");
                                        }
                                        args_undo->koa = koa;
                                        args_undo->fd = fildes;

                                        txc_tx_register_undo_action  (txd, x_open_undo, 
                                                                      (void *) args_undo, result,
                                                                      TXC_KOA_CREATE_UNDO_ACTION_ORDER);

                                        /* 
                                         * Don't need to explicitly release the lock on fildes 
                                         * because it is attached to KOA koa, so it will be  
                                         * released by the following operation:
                                         *   txc_koa_unlock_fds_refby_koa(koa);
                                         */
                                        txc_koa_unlock_fds_refby_koa(koa);
                                        txc_koa_unlock_alias_cache(koamgr);
                                        ret = fildes;
                                } else {
                                        /* 
                                         * CASE 2:
                                         * - KOA does not exist in the alias cache so there is no
                                         *   way for some other in-flight transaction to have a reference 
                                         *   to the file to operate on it.
                                         */
                                        txc_koa_create(koamgr, &koa, TXC_KOA_IS_FILE, (void *) inode);
                                        txc_koa_lock_fd(koamgr, fildes);
                                        txc_koa_attach_fd(koa, fildes, 0);
                                        sentinel = txc_koa_get_sentinel(koa);
                                        xret = txc_sentinel_tryacquire(txd, sentinel, 0);
                                        if (xret != TXC_R_SUCCESS) {
                                                TXC_INTERNALERROR("Cannot acquire the sentinel of the KOA I've just created!\n");
                                        }
                                        args_undo = (x_open_undo_args_t *)
                                                    txc_buffer_linear_malloc(txd->buffer_linear, 
                                                                             sizeof(x_open_undo_args_t));
                                        if (args_undo == NULL) {
                                                TXC_INTERNALERROR("Allocation failed. Linear buffer out of space.\n");
                                        }
                                        args_undo->koa = koa;
                                        args_undo->fd = fildes;

                                        txc_tx_register_undo_action  (txd, x_open_undo, 
                                                                      (void *) args_undo, result,
                                                                      TXC_KOA_CREATE_UNDO_ACTION_ORDER);

                                        txc_koa_unlock_fd(koamgr, fildes);
                                        txc_koa_unlock_alias_cache(koamgr);
                                        ret = fildes;
                                }
                        }
                        txc_stats_txstat_increment(txd, XCALL, x_open, 1);
                        break;
                case TXC_XACTSTATE_TRANSACTIONAL_IRREVOCABLE:
                case TXC_XACTSTATE_NONTRANSACTIONAL:
                        /* 
                         * Even if xCalls don't provide transactional properties when called
                         * outside of a transaction, we still need to create a KOA and assign
                         * a sentinel to be used later by any transactional xCalls. Thus we
                         * still need to properly synchronize accesses to internal data
                         * structures.
                         */
                        txc_koa_lock_alias_cache(koamgr);
                        if ((ret = fildes = txc_libc_open(pathname, open_flags, mode)) < 0) { 
                                txc_koa_unlock_alias_cache(koamgr);
                                local_result = errno;
                                goto done;
                        }
                        txc_koa_path2inode(pathname, &inode);
                        if (txc_koa_alias_cache_lookup_inode(koamgr, inode, &koa) 
                            != TXC_R_SUCCESS) 
                        {
                                txc_koa_create(koamgr, &koa, TXC_KOA_IS_FILE, (void *) inode);
                        }       
                        txc_koa_lock_fd(koamgr, fildes);
                        txc_koa_attach_fd(koa, fildes, 0);
                        sentinel = txc_koa_get_sentinel(koa);
                        txc_koa_unlock_fd(koamgr, fildes);
                        txc_koa_unlock_alias_cache(koamgr);
                        ret = fildes;
        }
done:
        if (result) {
                *result = local_result;
        }
        return ret;
}

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