Fix: mmap write() for large subbuffers and handle EINTR (v2)

[lttng-tools.git] / src / common / kernel-consumer / kernel-consumer.c

diff --git a/src/common/kernel-consumer/kernel-consumer.c b/src/common/kernel-consumer/kernel-consumer.c
index bbc31f8e3be14bdb3927c87a1aabb40e28e777b5..3c9687306dc2aa2e904ef35f9954bdcc37e1d436 100644 (file)
--- a/src/common/kernel-consumer/kernel-consumer.c
+++ b/src/common/kernel-consumer/kernel-consumer.c
@@ -49,7 +49,7 @@ ssize_t lttng_kconsumer_on_read_subbuffer_mmap(
                struct lttng_consumer_stream *stream, unsigned long len)
 {
        unsigned long mmap_offset;
-       ssize_t ret = 0;
+       ssize_t ret = 0, written = 0;
        off_t orig_offset = stream->out_fd_offset;
        int fd = stream->wait_fd;
        int outfd = stream->out_fd;
@@ -59,30 +59,40 @@ ssize_t lttng_kconsumer_on_read_subbuffer_mmap(
        if (ret != 0) {
                errno = -ret;
                perror("kernctl_get_mmap_read_offset");
+               written = ret;
                goto end;
        }
 
        while (len > 0) {
                ret = write(outfd, stream->mmap_base + mmap_offset, len);
-               if (ret >= len) {
-                       len = 0;
-               } else if (ret < 0) {
-                       errno = -ret;
+               if (ret < 0) {
+                       if (errno == EINTR) {
+                               /* restart the interrupted system call */
+                               continue;
+                       } else {
+                               perror("Error in file write");
+                               if (written == 0) {
+                                       written = ret;
+                               }
+                               goto end;
+                       }
+               } else if (ret > len) {
                        perror("Error in file write");
+                       written += ret;
                        goto end;
+               } else {
+                       len -= ret;
+                       mmap_offset += ret;
                }
                /* This won't block, but will start writeout asynchronously */
                lttng_sync_file_range(outfd, stream->out_fd_offset, ret,
                                SYNC_FILE_RANGE_WRITE);
                stream->out_fd_offset += ret;
+               written += ret;
        }
-
        lttng_consumer_sync_trace_file(stream, orig_offset);
-
-       goto end;
-
 end:
-       return ret;
+       return written;
 }
 
 /*
@@ -94,7 +104,7 @@ ssize_t lttng_kconsumer_on_read_subbuffer_splice(
                struct lttng_consumer_local_data *ctx,
                struct lttng_consumer_stream *stream, unsigned long len)
 {
-       ssize_t ret = 0;
+       ssize_t ret = 0, written = 0;
        loff_t offset = 0;
        off_t orig_offset = stream->out_fd_offset;
        int fd = stream->wait_fd;
@@ -107,8 +117,11 @@ ssize_t lttng_kconsumer_on_read_subbuffer_splice(
                                SPLICE_F_MOVE | SPLICE_F_MORE);
                DBG("splice chan to pipe ret %zd", ret);
                if (ret < 0) {
-                       errno = -ret;
                        perror("Error in relay splice");
+                       if (written == 0) {
+                               written = ret;
+                       }
+                       ret = errno;
                        goto splice_error;
                }
 
@@ -116,8 +129,18 @@ ssize_t lttng_kconsumer_on_read_subbuffer_splice(
                                SPLICE_F_MOVE | SPLICE_F_MORE);
                DBG("splice pipe to file %zd", ret);
                if (ret < 0) {
-                       errno = -ret;
                        perror("Error in file splice");
+                       if (written == 0) {
+                               written = ret;
+                       }
+                       ret = errno;
+                       goto splice_error;
+               }
+               if (ret > len) {
+                       errno = EINVAL;
+                       perror("Wrote more data than requested");
+                       written += ret;
+                       ret = errno;
                        goto splice_error;
                }
                len -= ret;
@@ -125,6 +148,7 @@ ssize_t lttng_kconsumer_on_read_subbuffer_splice(
                lttng_sync_file_range(outfd, stream->out_fd_offset, ret,
                                SYNC_FILE_RANGE_WRITE);
                stream->out_fd_offset += ret;
+               written += ret;
        }
        lttng_consumer_sync_trace_file(stream, orig_offset);
 
@@ -132,7 +156,7 @@ ssize_t lttng_kconsumer_on_read_subbuffer_splice(
 
 splice_error:
        /* send the appropriate error description to sessiond */
-       switch(ret) {
+       switch (ret) {
        case EBADF:
                lttng_consumer_send_error(ctx, CONSUMERD_SPLICE_EBADF);
                break;
@@ -148,7 +172,7 @@ splice_error:
        }
 
 end:
-       return ret;
+       return written;
 }
 
 /*
@@ -351,13 +375,14 @@ ssize_t lttng_kconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
 
                        /* splice the subbuffer to the tracefile */
                        ret = lttng_consumer_on_read_subbuffer_splice(ctx, stream, len);
-                       if (ret < 0) {
+                       if (ret != len) {
                                /*
                                 * display the error but continue processing to try
                                 * to release the subbuffer
                                 */
                                ERR("Error splicing to tracefile");
                        }
+
                        break;
                case LTTNG_EVENT_MMAP:
                        /* read the used subbuffer size */
@@ -369,7 +394,7 @@ ssize_t lttng_kconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
                        }
                        /* write the subbuffer to the tracefile */
                        ret = lttng_consumer_on_read_subbuffer_mmap(ctx, stream, len);
-                       if (ret < 0) {
+                       if (ret != len) {
                                /*
                                 * display the error but continue processing to try
                                 * to release the subbuffer